Conservation Science and Habitat Protection at Audubon ...egret.org/pdfs/Ardeid2006.pdf2006 the ARDEID page 1 The tidal waters that illuminate the coastal landscapes of Bolinas lagoon

◗ local wetlands

International

Importance

◗ non-native crustacean

Signal Crayfish

◗ protecting habitat

Heronry Life Span

◗ vernal pools

Nitrogen Pollution

◗ mapping ecosystems

Charting the Course

2006

the

Ardeid

Conservation Science and

Habitat Protection at Audubon

Canyon Ranch

Audubon Canyon RanchConservtion Science andHabitat Protection

Executive StaffSkip Schwartz, Executive DirectorJohn Petersen, Associate DirectorYvonne Pierce, Administrative DirectorScience StaffJohn Kelly, PhD, Director, Conservation Science

and Habitat ProtectionEmiko Condeso, Research CoordinatorDaniel Gluesenkamp, PhD, Habitat Protection

and Restoration SpecialistGwen Heistand, Bolinas Lagoon Preserve BiologistJeanne Wirka, Bouverie Preserve BiologistField BiologistsAmanda GardnerJennifer JordanMark McCaustlandMark RodgersLand StewardsBill Arthur, Bolinas Lagoon PreserveDavid Greene, Tomales Bay propertiesJohn Martin, Bouverie PreserveResearch AssociatesJules EvensHelen PrattRich StallcupResource Management AssociatesLen BluminRoberta Downey

the ARDEID 2006

Nancy Abreu (H); Ken Ackerman(D,G,R); Drew Alden (C); Leslie Allen(R); Sarah Allen (S); Janica Anderson(H); Bob Baez (S,W); Norah Bain (H);Bruce Bajema (H,S); Tom Baty (W);Sherm Bielfelt (G,R); GordonBennett (S); Mark Bir (R); Gay Bishop(S); Giselle Block (H); Len Blumin(R); Patti Blumin (H,R); EllenBlustein (H,S); Noelle Bon (H); JanetBosshard (H); Tom Bradner (E,R);Anna-Marie Bratton (E,R); EmilyBrockman (W); Shannon Burke (R);Kathy Burnell and Girl Scout Troop880 (R); Phil Burton (H); DeniseCadman (H); Ann Cassidy (H);George Clyde (W); Rig Currie (W);George Curth (H); Sandy Curth (H);Karen Davis (H); Melissa Davis (H,W); Jack Dineen (H); RobertaDowney (R); Joe Drennan (W); JudyDugan (E,R); Bob Dyer (H); GladysEllis (H); Jules Evens (C,S,W); KatieFehring (S,W); David Ferrera (W);John Finger (C); Binny Fischer(H,W); Carol Fraker (H); Harry Fuller(W); George Gamble (H); CassieGruenstein (W); Amanda Gardner(H,W); Tony Gilbert (H,S,W); BerylGlitz (H); Dohn Glitz (H) PhilipGreene (H); Madelon Halpern (H);Fred Hanson (S,W); Roger Harshaw(S); Christian Hellwig (H); DianeHichwa (H); Tom Hildreth (H); PatHildreth (H); Jake Hobson (H); KimHobson (H); Joan Hoffman (H);Roger Hothem (H); Lisa Hug (S,W);

Shelly Hughes (H); Jeri Jacobson (H);Rick Johnson (H,S,W); Gail Kabat(W); Guy Kay (H); RichardKirschman (S); Ellen Krebs (H); CarolKuelper (S); Eva Laevastu (H); JoanLamphier (H,W); Judy Laursen (R);Stephanie Lennox (H); Robin Leong(H); Eileen Libby (H); Joan Lippman(H); Art Magill (R); Lyn Magill (R);Julie Marlowe (W); Roger Marlowe(W); Diane Merrill (H); Jean Miller(H); Dan Murphy (S,W); Len Nelson(H); Wally Neville (H); Terry Nordbye(S,W); Ed Nute (S); Mariam Ortwerth(H); Peg Paulivitch (H); Tony Paz (E);Precious Peoples (H); Kate Peterlein(S); Ryan Phelan (H); Bob Pitts (H);Linda Reichel (H); Jeff Reichel (H);Rudi Richardson (W); Glenda Ross(D,G,R); Ellen Sabine (H); MarilynSanders (H); Phyllis Schmitt (H,R);Gordon Schremp (H); LaurieSchremp (H); Rob Schwartz (R);Alice Shultz (H); Joe Smith (W); PatSmith (H); Amy Southwick (R); AnneSpencer (S); Rich Stallcup (S);Barbara Starke (R); JeanStarkweather (H); Lowell Sykes (H,S);Judy Temko (H,S); Janet Thiessen(H); Melissa Thompson (H,S);Francis Toldi (W); Sheila Town (R);Susan Tremblay (R); Tanis Walters(S); Varia Walle (H); Jim White (S, W);Diane Williams (S); Phyllis Williams(H); Will Wilson (S,W); Wendy Wood(H); Patrick Woodworth (H,S,W);Katy Zaremba (C).

In this issue

International Importance: Habitat protection on Bolinas Lagoon and Tomales Bay ◗ by John P. Kelly ......................................................................................................................page 1

Singal Crayfish in Stuart Creek: Controlling Pacifastucus lenistulus at Bouverie Preserve ◗ by Jeanne Wirka ....................................................................................................................page 4

What’s the Life Span of a Heronry? Habitat protection and nesting colonies◗ by John P. Kelly ......................................................................................................................page 6

Sonoma Valley Vernal Pools: Is nitrogen pollution harming fragile ecosystems?◗ by Daniel Gluesenkamp and Jeanne Wirka ..........................................................................page 8

Charting the Course: The importance of mapping in the protection of native ecosystems◗ by Jennifer Jordan ................................................................................................................page 10

Cover: Invasive, non-native signal crayfish can measure up to 16 cm long. Photo by Mike Lane / AlamyArdeid masthead Great Blue Heron ink wash painting by Claudia Chapline

Volunteers for ACR research or habitat restoration projects since TheArdeid 2005. Please call (415) 663-8203 if your name should havebeen included in this list.

PROJECT CLASSIFICATIONS:C = Coastal Habitat Restoration at Toms Point ◆ D = Douglas Fir Manage-ment at Bouverie Preserve; ◆ E = Ehrharta erecta Removal at Bolinas LagoonPreserve ◆ G = Grassland Management at Bouverie Preserve ◆ H = Heron/Egret Research ◆ R = Invasive Plant Removal and Habitat Restoration ◆ S =Shorebird Censuses on Tomales Bay Shorebird Censuses ◆ W = Tomales BayWaterbird Census

The Watch

2006 the ARDEID page 1

The tidal waters that illuminate thecoastal landscapes of Bolinas lagoon

and Tomales Bay easily capture one’sattention. They trace the contours of theland and highlight the moods of coastalwind and weather. They mark the move-ments of waterbirds on the surface, mirrorflocks that sail overhead, and enhance thepower of sunsets. But these waters are notmerely captivating and beautiful: they areecologically special. Bolinas Lagoon andTomales Bay are two of 22 wetlands in theUnited States that have been designatedas wetlands of international importanceby the Convention on Wetlands (Figure 1).

Popularly known as the “RamsarConvention,” the Convention onWetlands is an intergovernmental treatyfor national action and international

cooperation for conservation (see box onpage 2). Key documents that substantiateRamsar designation address standard cri-teria (Table 1) by citing relevant scientificevidence. This article highlights suchwork by scientific investigators attractedto the rich and abundant life in BolinasLagoon and Tomales Bay.

Actually, Bolinas Lagoon and TomalesBay are part of a larger, relatively undis-turbed complex of wetlands along theMarin/Sonoma coast that includesDrakes and Limantour Esteros, AbbottsLagoon, Estero Americano, Estero SanAntonio, and Bodega Harbor. The near-ness of these wetlands to each other,along with their common geographicposition in the Pacific Flyway, connec-tions to the same coastal ocean waters,

and shared proximity to the urbanizedSan Francisco Estuary, results in a systemof estuaries that are likely to be intercon-nected in numerous ways.

For example, the neighboring wetlandsexhibit different hydrographic regimesand nutrient cycles. This creates a broadrange of habitat conditions, differences inthe timing and composition of species,and alternating opportunities for species

Habitat values in Bolinas Lagoon and Tomales Bay

International Importanceby John P. Kelly

Figure 1. Wetlands of international importance in the United States; numbers refer to the sequence ofrecognition by the Ramsar Convention: 1= Izembek National Wildlife Refuge (NWR); 2 = Forsythe NWR; 3= Okefenokee NWR; 4 = Ash Meadows NWR; 5 = Everglades National Park; 6 = Chesapeake Bay Estuar-ine Complex; 7 = Cheyenne Bottoms; 8 = Cache-Lower White Rivers; 9 = Horicon Marsh; 10 = CatahoulaLake; 11 = Delaware Bay Estuary; 12 = Pelican Island NWR; 13 = Caddo Lake; 14 = Connecticut RiverEstuary; 15 = Cache River-Cypress Creek Wetlands; 16 = Sand Lake NWR; 17 = Bolinas Lagoon; 18 =Quivira NWR; 19 = Tomales Bay; 20 = Tijuana River National Estuarine Research Reserve; 21 = GrasslandEcological Area; 22 = Kawainui and Hamakua Marsh Complex.

Table 1. Ramsar Criteria used to identify wetlandsof international importance1.

Importance for conserving representative, rare orunique wetland types

Criterion 1: contains a representative, rare, orunique example of a natural or near-natural wetland type found within theappropriate biogeographic region.

Importance for conserving species and ecologicalcommunities

Criterion 2: supports vulnerable, endangered, orcritically endangered species orthreatened ecological communities.

Criterion 3: supports populations of plant and/oranimal species important formaintaining the biological diversity ofa particular biogeographic region.

Criterion 4: supports plant and/or animal speciesat a critical stage in their life cycles, orprovides refuge during adverseconditions.

Importance for conserving taxonomic groupsCriterion 5: regularly supports 20,000 or more

waterbirds.Criterion 6: regularly supports 1% of the

individuals in a population of onespecies or subspecies of waterbird.

Criterion 7: supports a significant proportion ofindigenous fish subspecies, speciesor families, life-history stages, speciesinteractions and/or populations thatare representative of wetlandbenefits and/or values and therebycontributes to global biologicaldiversity.

Criterion 8: is an important source of food forfishes, spawning ground, nurseryand/or migration path on which fishstocks, either within the wetland orelsewhere, depend.

Criterion 9: regularly supports 1% of theindividuals in a population of onespecies or subspecies of wetland-dependent non-avian animal species.

1Adopted by the 7th (1999) and 9th (2005) Meetings of theConference of the Contracting Parties.

page 2 the ARDEID 2006

recruitment or recolonization betweensites. As a group, these wetlands supportcommon populations of mobile species,including the largest concentration ofharbor seals (Phoca vitulina) inCalifornia (Allen et al. 1989). BolinasLagoon and Tomales Bay are key compo-nents of this network of coastal estuaries,providing important foraging, breeding,nursery, and roosting grounds for a widevariety of coastal and estuarine species(Table 1, Criteria 1 and 3).

Estuaries along the west coast of NorthAmerica tend to be more dynamic, geo-morphologically, than in other regions ofthe continent, because of their relativelyrecent geologic history. This dynamism isamplified in Tomales Bay and BolinasLagoon by their association with the SanAndreas Fault, which underlies both sys-tems (Criterion 1). The fault-generatedconfiguration of Tomales Bay differs fromother smaller coastal estuaries and lagoonsin that approximately 90% of its 28.5 km2

area is subtidal, providing vast areas ofopen water through the tidal cycle. Thiscontrasts with the predominance of tidechannels and exposed mudflats during lowtide periods in Bolinas Lagoon.

The natural tidal landscapes of BolinasLagoon and Tomales Bay contributestrongly to the international significanceof these areas (Criteria 1 and 2). Rare andimportant habitat types in Tomales Bayinclude vast eelgrass beds that support arich diversity of birds, marine fishes, andinvertebrates (Criterion 2). The north endof the bay is mantled by one of the finestmobile sand dune systems along theCentral California coast, with unique duneslack wetland communities that formbetween the dunes (Criterion 2). BolinasLagoon supports a rich and relatively nat-ural balance of tidal sloughs, emergenttidal marsh, and transitional shorelinevegetation. It is important to rememberthat healthy emergent tidal marsh is rarein California estuaries because of wide-spread habitat degradation since the mid-1850s (Nichols et al. 1986).

Both estuaries provide habitat formany rare, threatened, and endangeredplant and animal species (Table 2; Table 1,Criterion 2). Among these is the beautifulsalt marsh annual, Point Reyes bird’s beak(Cordylanthus maritimus ssp. palustris),which forms colonies in numerous loca-tions where freshwater streams flow intotidal marshes (Kelly and Fletcher 1994).Both estuaries support impressive num-bers of the Salt Marsh CommonYellowthroat, an elegant and secretivewarbler and California Species of Special

Concern that thrives in well-establishedbrackish marshes (Hobson et al. 1985,Kelly and Wood 1996, Nur et al. 1997).Both estuaries provide wintering habitatfor the federally threatened WesternSnowy Plover (Charadrius alexandrinusnivosus), which suffers critically from theloss of undisturbed beaches (Page et al.1986; USFWS 1993). The natural transi-tions between salt marsh and upland veg-etation in both Tomales Bay and BolinasLagoon are of particular value, providinghigh-tide refugia and feeding areas for thestate-threatened California Black Rail andother tidal marsh species (Criterion 4;Evens et al. 1991).

Each rare or endangered species has aunique story related to important localhabitat values (Criterion 2). For example,the federally endangered myrtle’s silver-spot butterfly (Speyeria zerene myrtleae)is restricted to dune and grassland areasimmediately adjacent to the coast and isknown only from a few sites in northern

Marin County (Launer et al. 1994). It layseggs only on native violets, possibly onlyon Viola adunca, and is seriously threat-ened by habitat loss and invasions byEuropean beachgrass (Ammophila are-naria) and ice plant (Carpobrotus edulis).Current work by Audubon Canyon Ranchto remove these invasive species andrestore coastal dunes in northern TomalesBay could benefit this rare butterfly.

Long-term monitoringBolinas Lagoon and Tomales Bay are

extraordinary feeding areas for birds.Long-term studies of bird use have clearlyestablished the importance of these areasas Ramsar sites (Criteria 3–6). The abun-dance and diversity of waterbirds that useTomales Bay (Kelly and Tappen 1998,Kelly 2001a, Kelly and Stallcup 2003) andBolinas Lagoon (Shuford et al. 1989)reveal the biogeographic importance ofthese areas as over-wintering areas and,secondarily, as migratory stopover sites(Criterion 4). Episodic invasions ofanchovies in Bolinas Lagoon can attractspectacular numbers of roosting andfeeding Brown Pelicans (up to 6000) andhordes of Elegant Terns (also as many as6000; Shuford et al. 1989).

Shuford and others (1989) found thattwo-thirds of the 70 most numerous birdspecies using Bolinas Lagoon occurred aswinter residents. Bolinas Lagoon is also amajor spring staging area for migratingWestern Sandpipers (Shuford et al. 1989).During winter, Tomales Bay supports asmany as 25,000 waterbirds (877 km2; Kellyand Tappen 1998), up to 20,700 shore-birds (Kelly 2001a), and 10,000–20,000thousand gulls (mostly California Gulls;Criterion 5; Kelly et al 1996). Winter

The Ramsar ConventionThe Convention on Wetlands is an intergovernmental treaty adopted on 2

February, 1971, on the southern shore of the Caspian Sea, in the Iranian city ofRamsar. Consequently, it has become popularly known as the “Ramsar Convention.”Ramsar is the first of the modern global intergovernmental treaties on the conserva-tion of natural resources (http://ramsar.org).

Over the years, the Conference of the Contracting Parties (COP, the decision-making body of delegates from all the Member States) has kept the RamsarConvention abreast with changing world priorities and trends in environmentalthinking. When countries join the Convention, their first obligation is to designateone or more wetlands for inclusion in the List of Wetlands of InternationalImportance (the “Ramsar List”) and to promote their conservation. The Conventioncurrently has 152 Contracting Parties. More than 1600 wetlands have been desig-nated as Wetlands of International Importance, covering over 1.4 million km2, andthe list of wetlands continues to grow. The Convention’s mission is the conservationand wise use of wetlands through local, regional and national actions and interna-tional cooperation, as a contribution towards achieving sustainable developmentthroughout the world.

Table 2. Estimated numbers of species with specialconservation status in Tomales Bay and BolinasLagoon (Ramsar documents; Kelly and Stallcup2003, WRA et al. 1996, PWA and WRA 2006). Thenumbers of federally threatened or endangeredspecies are in parentheses.

Taxonomic group Tomales Bay Bolinas Lagoon

Plants 48 (6) 27* (2)*Invertebrates 9 (3) 11*Fishes 3 (3) 6*Reptiles 2 2 Amphibians 2 (1) 2 (1)Birds 48 (6) 25 (6)Mammals 8 8* (3)*

*special status species that “may occur or are known to occur”in Bolinas Lagoon (PWA and WRA 2006)


waterbird counts by Audubon CanyonRanch suggest that Tomales Bay may pro-vide the highest quality winter habitat forBufflehead on the West Coast south of theColumbia River (Kelly and Tappen 1998).In addition, Tomales Bay may support12% of the statewide Bufflehead numbers,6% of Surf Scoters, and 31% of BlackBrant (well above one percent of theworldwide population indicated byCriterion 6; Kelly and Tappen 1998).

Both sites provide important nestingand feeding areas for Great Blue Heronsand Great Egrets (Pratt 1983, Kelly et al.1993, Kelly et al. 2006) and valuable for-aging areas for the state’s largest nestingconcentration of Osprey (Evens 2000). Itis not surprising that several fundamen-tal aspects of shorebird ecology havebeen determined by field studies inthese rich and productive coastal sys-tems (e.g., Page and Whittaker 1975, Kus1985, Warnock et al. 1995, Kelly 2001b,Kelly and Weathers 2002).

Importance for fishesTomales Bay and Bolinas Lagoon are

enormously productive nurseries formarine and estuarine fishes (Criterion 7).Numerous species of surfperch (Embioto-cidae), distinguished by an impressivearray of color patterns and fin shapes,ride tidal currents in and out of theseestuaries. Leopard sharks (Thiakis semi-fasciata) forage along channel edges andover tidal flats, where they nip off clamsiphons and suck worms from the mud.Vast subtidal meadows of eelgrass(Zostera marina) in Tomales Bay are ofworldwide significance because of theirvalue as spawning substrate for an aver-age of 30–50 million Pacific herring(Clupea harengus pallasi) each year(Criterion 3; Suer 1987, Watanabe andWalters 2004). Work conducted at ACR’sCypress Grove Research Center showedthat tens of thousands of California batrays (Myliobatis californica) forage inten-sively for crustaceans and other inverte-brate prey over the inundated mudflats ofTomales Bay (Hopkins 2003).

A 1995 survey of published andunpublished sources documented theoccurrence of 163 species of fishes inTomales Bay and its watershed (Kelly andFox 1995), and California Fish and Gamesurveys have found at least 68 species offishes within Bolinas Lagoon (PWA et al1996, PWA and WRA 2006). Such varietyreflects the wide range of habitat condi-tions and salinity regimes found inhealthy coastal bays and lagoons.

Anadromous salmonids pass throughboth estuaries en route to spawning areasin tributary creeks. Federally threatenedCentral California coast steelhead(Oncorhynchus mykiss) have been docu-mented in Pine Gulch Creek, which flowsinto Bolinas Lagoon, and are believed tospawn in other suitable lagoon tributaries(Criteria 2, 7, and 8; PWA and WRA 2006).Anecdotal accounts indicate that federallythreatened coho salmon (O. kisutch) wereonce common in Pine Gulch Creek buthave since become rare (WRA et al. 1996,PWA and WRA 2006). Approximately 10%of California’s coho migrate throughTomales Bay and into Lagunitas andOlema Creeks to spawn and thereforerepresent a potentially critical part of theprotected population known as theCentral California “EvolutionarilySignificant Unit” (Criterion 9). In addi-tion, brackish tributaries of Tomales Bayhave been found to support the extremelyrare tidewater goby (Eucycloglobius new-berryi; Criterion 2), although the specieswas not detected in recent surveys.

The recognition of Bolinas Lagoon andTomales Bay as Ramsar sites estab-

lishes their national and internationalvalue. However, their futures remain chal-lenged by problems related to watershedprotection, habitat management, recre-ational pressure, invasive species, andother coastal management issues.Conservation science at Audubon CanyonRanch continues to work toward improv-ing habitat protection and stewardship ofthese and other wetlands in central coastalCalifornia.

References citedAllen, S. G., H. R. Huber, C. A. Ribic, and D. G. Ainley.

1989. Population dynamics of harbor seals in theGulf of the Farallones, California. California Fish andGame 75: 224-232.

Evens, J. G. 2000. Population size and reproductivesuccess of Osprey at Kent Lake, Marin County, CA –1999. Avocet Research Associates. Report to MarinMunicipal Water District, Corte Madera, CA.

Evens, J. G., G. W. Page, S. A. Laymon, and R. W.Stallcup. 1991. Distribution, relative abundance andstatus of the California Black Rail in western NorthAmerica. Condor 93: 952-966.

Hobson, L., P. Perrine, E. B. Roberts, M. L. Foster, P.Wooden. 1986. A breeding season survey of Saltmarsh Common Yellowthroats (Geothlypis trichassinuosa) in the San Francisco Bay region. SanFrancisco Bay Bird Observatory report to the U. S.Fish and Wildlife Service, Sacramento, CA.

Hopkins, T. E., and J. J. Cech. 2003. The influence ofenvironmental variables on the distribution andabundance of three elasmobranchs in TomalesBay, California. Environmental Biology of Fishes66: 279-291.

Kelly, J. P. 2001a. Distribution and abundance of wintershorebirds on Tomales Bay, California: implicationsfor conservation. Western Birds 32: 145-166.

Kelly, J. P. 2001b. Hydrographic correlates of winterDunlin abundance and distribution in a temperateestuary. Waterbirds 24(3): 309-322.

Kelly, J. P., K. Etienne, C. Strong, M. McCaustland, andM. L. Parkes. 2006. Annotated atlas and implicationsfor the conservation of heron and egret nesting

colonies in the San Francisco Bay area. AudubonCanyon Ranch. ACR Technical Report 90-3-17[online: http://www.egret.org].

Kelly, J. P., J. G. Evens, R. W. Stallcup, and D.Wimpfheimer. 1996. The effects of aquaculture onhabitat use by wintering shorebirds. California Fishand Game 82(4): 160-174.

Kelly, J. P., and G. Fletcher. 1994. Habitat correlates anddistribution of Cordylanthus maritimus(Scrophulariaceae) on Tomales Bay, California.Madroño 41:316-327.

Kelly, J.P, and K. J. Fox. 1995. Fish species of TomalesBay and its watershed. The Tomales Bay Association,Point Reyes Station, CA.

Kelly, J. P., H. M. Pratt, and P. L. Greene. 1993. Thedistribution, reproductive success, and habitatcharacteristics of heron and egret breedingcolonies in the San Francisco Bay area. ColonialWaterbirds 16:18-27.

Kelly, J. P., and R. W. Stallcup. 2003. Documentedoccurrences of bird species on Tomales Bay,California, prior to January 2003, and a protocol forfuture bird species inventories. A report to the PointReyes National Seashore and the All TaxaBiodiversity Inventory of Tomales Bay. ACR Tech.Rpt. 89-12-6. Audubon Canyon Ranch, Marshall, CA94940. 103 pp

Kelly, J. P., and S. L. Tappen. 1998. Distribution, abun-dance, and implications for conservation of winterwaterbirds on Tomales Bay, California. Western Birds29: 103-120.

Kelly, J. P., and C. Wood. 1996. Within-season and diur-nal variation in foraging behavior of the CommonYellowthroat. Condor 98: 491-500.

Kelly, J. P., and W. W. Weathers. 2002. Effects of feedingtime constraints on body mass regulation andenergy expenditure in wintering Dunlin (Calidrisalpina). Behavioral Ecology 13: 766-775.

Kus. B. E. 1985. Aspects of flocking behavior and pred-ator avoidance in wintering shorebirds. Ph.D. disser-tation, University of California, Davis.

Launer, A.E., D.D. Murphy, J.M. Hoekstra and H.R.Sparrow, 1994. The endangered Myrtle’s silverspotbutterfly: present status and initial conservationplanning. Journal of Research on the Lepidoptera 31(1-2): 132-146

Nichols, H., J. E. Hoern, S. N. Luoma, and, D. H.Peterson. 1986. The modification of an estuary.Science 231: 567-573.

Nur, N., S. Zack, J.G. Evens and T. Gardali. 1997. Tidalmarsh birds of the San Francisco Bay region: status,distribution and conservation of five Category 2taxa. Final report to the U. S. Geological Survey -Biological Resources Division.

Page, G. W., F. C. Bidstrup, R. J. Ramer, and L. E.Stenzel. 1986. Distribution of wintering SnowyPlovers in California and adjacent states. WesternBirds 17: 145-170.

Page, G. W., and D. F. Whitacre. 1975. Raptor predationon wintering shorebirds. Condor 77: 73-83.

Pratt, H. 1983. Marin County California heroncolonies. Western Birds 14: 169-184.

PWA and WRA. 2006. Projecting the future evolution ofBolinas Lagoon. Public draft prepared for the MarinCounty Open Space District by Philip Williams &Associates, Ltd, in association with WetlandResearch Associates, Inc. Philip Williams andAssociates, San Francisco, CA.

Shuford, D. W., G. W. Page, J. G. Evens, and L. E.Stenzel. 1989. Seasonal abundance of waterbirds atPoint Reyes: a coastal California perspective.Western Birds 20: 137-265.

Suer, A. L. 1987. The herring of San Francisco andTomales Bays. Ocean Research Institute, SanFrancisco.

USFWS (U. S. Fish and Wildilfe Service). 1993.Determination of Threatened Status for the PacificCoast population of the Western Snowy Plover.Federal Register 58: 12864-12874.

Warnock, N. G., W. Page, and L. E. Stenzel. 1995. Non-migratory movements of Dunlins on their Californiawintering grounds. Wilson Bulletin 107: 131-139.

Watanabe, R. T., and K. Walters. 2004. Summary ofthe 2003-2004 pacific herring spawning seasonand commercial herring fishery for Tomales Bay.California Department of Fish and Game report[online:http://www.dfg.ca.gov/mrd/herring/archive.html].

WRA (Wetlands Research Associates), Philip WilliamsAssociates, and Avocet Research Associates. 1996.Bolinas Lagoon Management Plan Update. MarinCounty Open Space District, San Rafael, CA.


Ahike to the waterfall through theshady coolness of Stuart Canyon,

preferably punctuated by frequentencounters with newts on the CanyonTrail, continues to be the highlight formost visitors to the Bouverie Preserve.And no wonder. Stuart Creek, with itsperennial flows, excellent water quality,and wide array of aquatic microhabitats,is one of the most pristine and biologi-cally diverse creeks in Sonoma County.The Bouverie Preserve is also one of thefew places in California where the rangesof all three newt species found west of theRocky Mountains (California, red-bellied,and rough-skinned) overlap. While newtshave long ruled the roost at Bouverie,data from a recent study of amphibians atthe Preserve have shed light on a poten-tially major threat to the continued repro-ductive success of all three newt species,as well as other aquatic taxa: that poten-tial threat is the signal crayfish(Pacifastucus lenisculus).

The signal crayfish is a relatively large,freshwater crustacean native to theKlamath Basin (mostly Oregon andWashington but also north of the KlamathRiver in California) and southwesternCanada. This western version of the tasty“crawdad” species found elsewhere in theU.S. has been observed in Stuart Creek forat least 15 years (John Petersen, personalcommunication). While the impact of thecrayfish on native fauna in Stuart Creekhas not been studied directly, ample evi-dence exists from other sites in Californiathat invasive crayfish negatively affectamphibians such as the Pacific treefrog(Hyla regilla), foothill yellow-legged frog (Rana boylii), and California newt(Taricha torosa) (Cook 2005, Gambrantand Katz 1996, Gambrant et al. 1997, GISD2006, Watters et al. 2004), all of which arefound in Stuart Creek.

Since the early 1900s, signal crayfishhave been introduced multiple times intorivers and lakes in more southerly parts ofCalifornia, in other western states, inEurope, and in Japan. Highly competitivewith other crayfish species, the signal

crayfish has causedthe extirpation ordecline of indige-nous crayfishspecies wherever ithas been intro-duced. In California,it is implicated inthe extinction of thesooty crayfish (P.nigrescens), onceendemic to SanFrancisco Bay, and iscurrently threaten-ing the narrowly-endemic Shastacrayfish (P. fortis), astate- and federally-listed endangeredspecies found onlyin Shasta County.Because they areopportunistic, poly-trophic feeders, sig-nal crayfish alongwith other invasivecrayfish species,such as the redswamp crayfish(Procambarusclarkii) from thesoutheastern U.S.,can also have a dev-astating impact onother aquatic taxa,including macro-invertebrates, fish,amphibians, andaquatic plants (GISD2006, Griffiths et al.2004, Kerby et al.2005, Light 2004, Watters et al. 2004). Theyprey on native aquatic species’ eggs andlarvae and compete with juveniles andadults of native species for shelter that isneeded for protection from predators(Griffiths et al. 2004; Light 2004).

In his recent study of amphibians atthe Bouverie Preserve, herpetologistDavid Cook made several findings thatsuggest that signal crayfish may be having

a significant negative impact on nativeamphibians in Stuart Creek (Cook 2005).Cook found that larval red-bellied newts(Taricha rivularis) were found in muchhigher concentrations in the upperreaches of Stuart Creek where crayfish areabsent, even though adults were presentin all reaches of the stream surveyed. Inother local streams, red-bellied newts donot appear to demonstrate a preference

Controlling Pacifastucus lenisculus at the Bouverie Preserve

Signal Crayfish in Stuart Creekby Jeanne Wirka

Figure 1. The Lower and Upper dams along Stuart Creek, on the Bouverie Pre-serve, may be important in controlling invasions by non-native, signal crayfish.

Figure 2. The Lower Dam flow outlet on Bouverie Preserve’s Stuart Creek.The presence of thick “ladder” vegetation on the right and under the flowingwater could facilitate the movement of non-native crayfish.

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for breeding in upstream habitats and lar-val newt distribution would be expectedto be the same as the distribution ofadults (David Cook, personal communi-cation). Cook was also unable to locateany larval California newts in summer of2005, even though egg masses had beenpresent in May 2005. These egg masseswere found in the lower reach of the creekwhere crayfish numbers appeared to behighest. Rough-skinned newts (Tarichagranulosa) may be similarly impacted.Finally, while adult foothill yellow-leggedfrogs are found at the preserve, Cookfound no evidence of successful breeding,even though certain reaches of StuartCreek provide excellent breeding habitat.The foothill yellow-legged frog is listed asa Species of Special Concern by theCalifornia Department of Fish and Game.

While these findings are not encourag-ing, the good news is that the distributionof crayfish in Stuart Creek offers a rareopportunity to both study and potentiallyeradicate or significantly reduce theirnumbers by taking advantage of high-velocity flows and existing barriers toupstream dispersal. At sites in other partsof California, researchers have found thatsome portion of crayfish populations inhigh-velocity streams will wash down-stream during high-flow events in winter,only to disperse back upstream as flowssubside (Kerby et al. 2005; Watters et al.2004). It is likely that this same patternoccurs during high-flow events at StuartCreek (David Cook, personal communica-tion). This seasonal “flushing” has beenshown to be an important opportunity toactively control re-invasion of streams byinvasive crayfish, especially where barri-ers exist to limit recolonization upstream(Kerby et al. 2005, Watters et al. 2004).

Cook’s surveys of Stuart Creek foundthat signal crayfish had invaded abovethe first abandoned concrete dam,located on Sonoma Land Trust Propertynear the entrance to the Canyon Trail(Lower Dam), but not above the secondabandoned concrete dam, locatedbetween Creek Access 4 and 5 (UpperDam; Figure 1). Physical inspection of thetwo dams confirmed that the lower damappears to be more accessible to crayfishdue to encroachment of entwined rootsand other aquatic vegetation, whereasthe lack of similar “ladder” vegetation orconcrete on the Upper Dam appears topresent a substantial barrier to crayfishdispersal (Figure 2).

The presence of barriers has beenshown to be an important factor in suc-cessful control of invasive crayfish inother California streams. Trapping or net-ting alone, in the absence of barriers,does nothing to prevent future reinvasion.However, trapping or netting after high-flow events, where a natural or man-madebarrier to recolonization exists, can create“crayfish-free” zones that may alleviatepredation pressure on native amphibianpopulations (Gambrant et al. 1997,Watters et al. 2004).

Building on findings from other sites inCalifornia, Bouverie staff have launchedthe first phase of what we hope will be amulti-year effort to control and study theinvasion of signal crayfish in Stuart Creek.The timing could not be better, as Cook’s(2005) study quantified relative abundancesof amphibians in Stuart Creek and pro-vides baseline data to assess the effects ofcrayfish eradication. The objectives of thefirst phase of the project are to quantifythe distribution of signal crayfish in StuartCreek and to fortify the existing human-made barriers to upstream dispersal. The

fortification will include theremoval of any ladder vegeta-tion and installation of metalflashing to create a slippery,vegetation-free surface thatthe crayfish cannot climb. Wewill also be monitoring closelyto see if the barriers cause anynegative consequences fornative species. They shouldnot affect upstream migrationof steelhead fry, because thatoccurs during periods of highflow, when water will be flow-ing well above the barrier.Nor should they affect move-ment of adult amphibians,which can crawl on land, andno other native species in

Stuart Creek is known to “crawl”upstream (David Cook, personal commu-nication). Next spring and summer, wewill also monitor the effects of theenhanced barriers on crayfish dispersalupstream.

Our hope is that high-flow events inStuart Creek may eventually take care ofthe bulk of the crayfish problem naturally,by washing the crayfish below the barri-ers. The project also includes some initialpilot trapping to assess the need and fea-sibility of larger-scale trapping after flowevents, to eradicate remaining individu-als. The long-term goal is to assesswhether the hoped-for declines in cray-fish abundance increase the breedingsuccess of native amphibians at Bouverie,thus protecting the long-term biologicaldiversity of the Preserve.

References citedCook, D. 2005. Amphibians of Bouverie Preserve.

Unpublished study prepared for Audubon CanyonRanch. 22 pages.

Gambrant, S. C, and L. B. Kats. 1996. Effect of intro-duced crayfish and mosquito fish on Californianewts. Conservation Biology 10: 1155-1162.

Gambrant, S. C., L. B. Kats, and C.B. Anzalone. 1997.Aggression by non-native crayfish deters breedingCalifornia newts. Conservation Biology 11: 793-796.

GISD (Global Invasive Species Database). 2006.Pacificus leniusculus. Website of the IUCN/SSCInvasive Species Specialist Group (ISSG) athttp://issg.appfa.auckland.ac.nz/database/species/ecology.asp?si=725&fr=1&sts=sss. Accessed on May30, 2006.

Griffiths, S. W., P. Collen, and J. D. Armstrong. 2004.Competition for shelter among over-winteringsignal crayfish an juvenile Atlantic salmon. Journalof Fish Biology 65: 436-447.

Kerby, J. L., S. P. D. Riley, L. B. Kats, and P. Wilson. 2005.Barriers and flow as limiting factors in the spread ofan invasive crayfish (Procambarus clarkia) in south-ern California streams. Biological Conservation 126:402-409.

Light, T. 2004. Behavioral effects of invaders: aliencrayfish and native sculpin in a California stream.Biological Invasions 7: 353-367.

Watters, T., L. Jones, S. O’Hare, M. Kerby, and L. Kats.2004. Seasonal removal of invasive stream predatorsto protect sensitive amphibian populations. Posterat the Ecological Society of America 2004 AnnualMeeting.

Gerritt Van Sickle, of ACR's Juniper Program, helps with Stuart Creek field work.A signal crayfish is retrieved.

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Some heronries seem to be permanentfeatures of coastal or wetland land-

scapes. As centers of intensive nestingactivity, such sites become conspicuousreminders that our environment is funda-mentally natural, driven by ecologicalprocesses that continue year after year. Butnature is always changing, and the long-term persistence of colony sites is rare.

In fact, heronries are often desertedafter only a few years, as new colonies areroutinely established in alternative loca-tions. This process is an important aspectof heron and egret nesting biology, allow-ing the birds to respond adaptively to nestdisturbance, shifts in wetland hydrology,and changes in the quality of nearby feed-ing areas. The extent to which these birdsdepend on existing colony sites can bedifficult to measure. Some clues can befound in the persistence patterns ofheronries monitored for many years.

The nesting colony at AudubonCanyon Ranch’s Picher Canyon nearBolinas Lagoon has persisted far longerthan most other colony sites in our region.Helen Pratt (1983) determined that theheronry has probably been active since atleast the early 20th century and couldhave been active as farback as the late 1800s,but its actual age is un-known. Although theabundances of nestingherons and egrets in theSan Francisco Bay regionare stable or increasing(Kelly et. al 2006), thesizes of particular colo-nies such as the one atACR’s Picher Canyon canbe impressively dynamic,as nesting birds moveamong colony sitesbetween years (Figure 1).New colonies are ofteninitiated with a few nestsand grow, either gradu-ally or abruptly, intolarger colonies in subse-quent years.

The number of consecutive years thatheronries remain active is closely relatedto the number of nests in the colony andthe species that nest there. The relation-ship between colony size and persistenceis evident in the regional dynamics ofcolony sites. In 1991–2005, an average of73 active colony sites supported approxi-mately 62 Great Blue Heron colonies, 25Great Egret colonies, 13 Black-crownedNight-Heron colonies, and 12 SnowyEgret colonies each year. Based on obser-vations from these sites, almost all activeheronries in any year are likely to havebeen active during previous years, butsmaller colonies of less than five neststend to become inactive within five yearsunless they reach higher levels of nestabundance associated with increasingpersistence (Figure 2).

Great Blue Heron colonies generallybecome inactive within five years if theyremain smaller than six nests, but theytend to persist, on average, for 12 or moreyears if they grow to more than 20 nests(Figure 3). The persistence of Great Egret,Black-crowned Night-Heron, andSnowy Egret colonies increases sub-stantially only after reaching an abun-

dance of 20–30 nests per species. Colonysites with less than ten nests of all speciescombined tend to remain active, on aver-age, for approximately eight years (Figure3). These general patterns probablyunderestimate the average persistence ofheronries, because some sites were activeprior to discovery or will remain activebeyond the 15-year monitoring period.However, the results show clearly that thenumber of years a colony site is occupiedis closely related to maximum colony size.

In general, the regional persistencepatterns of heronries suggest that conser-vation efforts should prioritize the protec-tion of colony sites with 20 or more activenests and that long-term protection ismost appropriate for colony sites withmore than 100 nests. However, theprotection of smaller colonies should notbe ignored, because they may be moresensitive to disturbance or prone toabandonment than larger colonies. Theimportance of protecting mixed-speciesheronries is enhanced by the presence ofadditional nesting species, and values

Habitat protection and nesting colonies

What’s the life span of a heronry?

by John P. Kelly

Figure 1. Annual number of nesting Great Blue Herons (solid bars)and Great Egrets (hatched bars) at ACR’s Bolinas Lagoon Preserve.

Figure 2. Relationship between the maximum size ofheronries (all species) and the number of consecutiveyears occupied, in the San Francisco Bay area, 1991-2005. (Note that maximum colony size is plotted on alog10 scale; trend lines represent Cleveland’s robust local-ly weighted regression algorithm, LOWESS, f = 0.6;Cleveland 1979).


associated with the expected longevity ofany heronry grow rapidly as nest abun-dance increases above six Great BlueHeron nests, 20 Great Egret nests, or 30Snowy Egret or Black-crowned Night-Heron nests (Figure 3).

Nesting habitat valuesShifts in the distribution of nesting

herons and egrets reflect their behavioralresponses to rapid changes in habitatvalue. Such responses reveal not only theresilience of herons and egrets to wet-land loss or degradation, but also theirability to benefit from localized habitatrestoration efforts. For example,increases in the number of herons andegrets nesting in San Pablo Bay marshessince the late 1990s coincided withincreases in the extent of restored tidalmarshes (Kelly et al. 2006).

We have also noticed that new colonysites are often initiated within a few kilo-meters of heronries that were disturbedby nest predators or humans. A mixedcolony of Snowy Egrets, Black-crownedNight-Herons, and Cattle Egrets hasapparently persisted for many years in thevicinity of Santa Rosa Creek in SonomaCounty, by repeatedly moving to newsites—at least four times since 1990—

after abandoningsites subjected tovarious forms ofhuman disturbance.The birds’ capacityto tolerate continu-ing disturbance inorder to nest in thisarea is unknown. Insome areas, ascarcity of alterna-tive colony sites insuitable locationsmight limit theresilience of heronsand egrets to the lossof nesting habitat or,alternatively, preventthem from takingfull advantage ofrestored wetlands.Therefore, the con-servation of alterna-tive colony sites maybe an important partof regional habitatprotection forherons and egrets.

The abandon-ment of heronries isusually associatedwith disturbance by

humans or predators. Sometimes, heron-ries are recolonized after a few years ofinactivity, but this apparently occurs onlyrarely. Normally, herons and egrets seemto avoid previously abandoned sites. Forexample, in the early 1990s as many as 29pairs of Great Blue Herons nested in thedense oak canopy of an isolated island inStafford Lake near Novato. The site wasabandoned in 1993, when a temporarydrop in water level resulted in a landbridge that allowed one or more raccoonsto raid the nests. Lake managers havesince kept water levels high enough toprevent land predators from gainingaccess to the island, but the site has notbeen recolonized. Apparently, the value ofnesting habitat is influenced by its history.

Ecosystem effects of colonysite protection

During the nesting season, herons andegrets tend to forage within a few to sev-eral kilometers of their colony sites (e.g.,Custer and Osborne 1978, Kelly et al.2005). Some investigators have suggestedthat a scarcity of suitable colony sitescombined with a tendency to forage nearnesting areas could limit or reduce heronor egret use of an entire wetland area orsubregion (Gibbs et al. 1987, Fasola and

Alieri 1992). Although most wetland land-scapes in California seem to provideplenty of suitable nesting habitat, colonysite preferences are very difficult to pre-dict, and changes in the number of locallynesting pairs can be considerable.

For example, from 1991 to 2002Tomales Bay supported, on average, 47 ±4 (SE) pairs of Great Egrets per year, but in2003–2005, after two of the three colonysites in the area were abandoned, thenumber of pairs declined to 18 ± 2 pairs.If the loss of local heronries leads to asubstantial decline in foraging activity bythese top predators, the abundance orbehavior of prey species or competingpredators might be affected. Such effectsmight, in turn, alter other ecosystemprocesses.

The loss of a local heron or egretcolony may also alter ecological processesin other areas. Such effects were sug-gested in 1994, when the virtual abandon-ment of the Snowy Egret colony on theMarin Islands, near San Rafael, appar-ently resulted in a dramatic influx ofapproximately 100 nesting pairs ofSnowies at a colony site in Napa County.

Many people share a sense that every-thing in nature is somehow connectedand that local events can affect (or beaffected by) events or processes in otherareas. Nesting herons and egrets are goodexamples of animals that depend stronglyon local resources while respondingadaptively to opportunities across largeregional landscapes. Over time, theregional management of wetland habitatsmay benefit not only from protectinglocal heronries, but also by responding tothe shifting distributions of nestingherons and egrets.

References CitedCleveland, W. S. 1979. Robust locally weighted regres-

sion and smoothing scatterplots. Journal of theAmerican Statistical Association 74: 829-836

Custer, T. W., and R. G. Osborn. 1978. Feeding habitatuse by colonially-breeding herons, egrets, and ibisesin North Carolina. Auk 95: 733-743

Fasola, M., and R. Alieri. 1992. Conservation ofheronry Ardeidae sites in North Italian agriculturallandscapes. Biological Conservation 62-219-228

Gibbs, J. P. S. Woodward, M. L. Hunter, and A. E.Hutchinson. 1987. Determinants of Great BlueHeron colony distribution in coastal Maine. Auk104: 38-47.

Kelly, J. P., K. L. Etienne, D. Stralberg, and M.McCaustland. 2005. Landscape use by herons andegrets in the San Francisco Estuary. State of theEstuary Conference [online: http://www.irwm.org],Oakland, CA.

Kelly, J. P., K. Etienne, C. Strong, M. McCaustland, andM. L. Parkes. 2006. Annotated atlas and implicationsfor the conservation of heron and egret nestingcolonies in the San Francisco Bay area. AudubonCanyon Ranch. ACR Technical Report 90-3-17[online: http://www.egret.org].

Pratt, H. M. 1983. Marin County, California heroncolonies, 1967-1981. Western Birds 14: 169-184.

Figure 3. Relationships between the maximum size of heronries and thenumber of consecutive years occupied, in the San Francisco Bay area, 1991-2005. (Note that maximum colony size is plotted on a log10 scale; trend linesrepresent Cleveland’s robust locally weighted regression algorithm, LOWESS,f = 0.6; Cleveland 1979).


Vernal pools are unique and sensitiveecosystems that form only where

topographic basins collect rainwater andsoil conditions prevent drainage. Eachpool is a discrete watershed that sup-ports a specialized suite of native plants.Vernal pools are famous for their highlyadapted wildflower species, includingshort-stature “belly plants”—many ofwhich can live nowhere else.Unfortunately, vernal pools are indecline statewide, due chiefly to humandevelopment of the flat and easily pavedwetlands. As a result, many of the plantand animal taxa associated with themare now rare or threatened with extinc-tion. However, even after pools are pro-tected from development they often suf-fer losses in species diversity, due tocompetition from invasive non-nativespecies. In this respect, the pools atAudubon Canyon Ranch’s BouveriePreserve are similar to many other pro-tected pools in Sonoma County.

Vernal pools at Bouverie Preserve aredominated by invasive species, such asItalian ryegrass (Lolium multiflorum)and velvet grass (Holcus lanatus), andlack many of the characteristic low-stature, vernal-pool plant species, eventhough these plants are present in nearbyuninvaded habitat (Gluesenkamp 2005).For example, at Bouverie the rare dwarfDowningia (Downingia pusilla) has beenlost from the vernal pools in which itonce occurred: these rare plants are sim-ply too short to germinate and growwhen buried beneath the deep carpet ofinvasive grasses. Similar losses haveoccurred at protected pools throughoutSonoma County.

Loss of unique endangered plantspecies from protected habitat is a con-servationist’s nightmare. Protecting habi-tat from development is supposed tosave the species that live there! Unfortu-nately, loss of biological diversity fromnature preserves is far too frequent an

occurrence. We are increasingly learningthe painful lesson that our protectedlands cannot remain biologically diversewithout active management—that“benign neglect” is equivalent to aban-doning sensitive species to perish in ahuman-altered world. While we arelearning that we must (paradoxically)tend to nature in order to save what isnatural, we are also learning that weknow relatively little about how thesenatural systems function.

Research recently initiated at ACR’sBouverie Preserve will test one hypothesisfor why some vernal pools lose nativeplant diversity, and will hopefully providesolutions for rescuing and restoring theserare and beautiful organisms. Specifically,we are investigating whether the invasionof non-native grasses in Bouverie’s vernalpools has been facilitated by eutrophica-tion originating from automobile trafficon the nearby highway.

Nitrogen addition: too much ofa good thing?

The enrichment of an ecosystem viathe addition of chemical nutrients, knownas “eutrophication,” has been studied inlakes and streams for decades. Researchand advocacy by W. Thomas Edmonsonin the 1950s saved Lake Washington froma stinky death and was an important stepin the development of modern naturalresource management (NRC 1999). Whilethe best-known examples of eutrophica-tion generally involve a slimy greenmuck-covered pond filled with suffocat-ing fish, the same processes can operateon land. For example, eutrophication onland might take the form of a rye grass“bloom” that covers a grassland and out-competes the smaller plants underneath.

Eutrophication can occur when anecological system receives addition ofnutrients that are otherwise in short sup-ply. In terrestrial systems nitrogen is typi-cally the element most limiting to growthof plants. Farmers have known this forcenturies and so increase yields by addingnitrogen fertilizer. Nitrogen limitation of

Is nitrogen pollution from vehicles harming fragile ecosystems?

Sonoma Valley Vernal Pools

by Daniel Gluesenkamp and Jeanne Wirka

Figure 1. Passive nitrogen sampling station at Bouverie Preserve.

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plant growth may seem counter-intuitive,because 78 percent of our atmosphere ismade up of nitrogen in the form of ele-mental nitrogen gas (N2). However, veryfew living things can break down N2 toacquire the nitrogen atoms needed tobuild amino acids and other nitrogen-containing compounds. Although Earth’satmosphere is predominantly nitrogen,plants and animals only have access tovery small quantities of reactive nitrogencompounds, such as ammonium (NH4)and nitrate (NO3). This is one of the greatironies of the natural world, comparableto the Ancient Mariner’s lament of “Water,water everywhere, Nor any drop to drink.”

In recent decades, human addition ofnitrogen worldwide has doubled the rateof nitrogen entering terrestrial systems,with very significant consequences fornitrogen-limited natural systems (Vitouseket al. 1997). Automobiles and trucks emitlarge quantities of nitrogen compounds,primarily nitrogen oxides (NOx) that areavailable for uptake by plants. In the early1990s automobiles in the United Statesbegan using catalytic converters that canover-reduce combustion NOx to ammonia(NH3) when they are running fuel rich.Nitrogen compounds produced by auto-mobiles are available to plants either bydirect absorption through stomata, viadry deposition on leaf surfaces, or throughroots after transfer to the soil. Consequent-

ly, automobiles might be fertilizing near-by vernal pool vegetation in the samemanner that large urban and agriculturalpollution plumes fertilize downwindecosystems.

A growing body of evidence suggeststhat dry deposition of nitrogen compoundsfrom fuel combustion is having signifi-cant ecological effects on sensitive eco-systems downwind of cities or adjacent tohighways through the West (Fenn et al.2003). Pollution from vehicles also hasbeen shown to change soil chemistry,produce phytotoxic levels of ozone withmajor ecological and economic conse-quences in forests, and dramaticallyimpact sensitive lichen communities.Added nitrogen can shift communitycomposition towards “nitrophilic”species, especially fast- growing non-native weeds that take advantage of theextra fertilization and out-compete nativespecies. In southern California drydeposition of nitrogen compounds is onefactor driving the conversion of chaparralshrublands to European annual grass-lands (Fenn et al. 2003). Stuart Weiss, ourcollaborator on the Bouverie Preservestudy, found evidence that dry depositionfrom Interstate 280 enabled Italianryegrass to out-compete native wild-flowers in Santa Clara County, leading tothe decline of endangered checkerspotbutterflies (Weiss 1999).

What’s going on in Bouverie’svernal pools?

Bouverie Preserve’s seasonal wetlandsare adjacent to California Highway 12, aroad on which approximately 15,000 vehi-cles pass by each day (Figure 2). Prelimi-nary estimates indicate that nitrogen dep-osition in this portion of Sonoma Countymay be as high as 5–10 kilograms N perhectare per year (G. Tonnesen, CE-CERT,UC Riverside, pers. com.), and these ratesmay be greater adjacent to Highway 12.Nitrogen deposition rates at this sitecould be on the order of those leading toeutrophication of other arid and semi-arid ecosystems. Vernal pools occur onshallow soils that are strongly nitrogenlimited, and the plant communities in ourpools are being smothered beneath acanopy of Italian ryegrass, a speciesknown to respond strongly to dry nitro-gen deposition. It seems likely that exclu-sion of Bouverie’s vernal pool plantsresults at least partly from the effects ofnitrogen pollution from the adjacenthighway on the growth of invaders suchas Italian ryegrass.

In April 2006 we initiated a project thatwill begin to test this hypothesis. Thestudy is a collaboration between ACR staffand Dr. Stuart Weiss, of the Menlo Park-based Creekside Center for EarthObservations, an expert on assessing theeffect of nitrogen deposition on plantcommunities. This first study will quantifynitrogen dry deposition near Highway 12and will determine how deposition rateschange with distance from Highway 12.Results will tell us whether depositionrates are in the range that has been eco-logically significant in other studies.

This deposition study relies on aninnovative sampling technology that usespre-treated cellulose pads to passivelysample 5 relevant chemical compounds(NOx, NO2, NH3, O3, HNO3). The padsare placed in small plastic vials that per-mit flow of the ambient atmosphere.Chemicals on the pads react with nitro-gen compounds in the atmosphere andenable us to determine the concentrationof each compound over the samplingperiod. We mounted passive samplers on3-m poles at eight locations in proximityto Bouverie Preserve’s vernal pools (Figure1). Five stations were established onBouverie Preserve land east of Highway12, and three stations were establishedwest of the highway in the Sonoma ValleyRegional Park. This will enable us to com-pare how wind direction influences the

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Figure 2. Location of nitrogen deposition sampling stations at ACR’s Bouverie Preserve and theadjacent Sonoma Valley Regional Park. Bouverie Preserve is shown with white cross-hatchedlines, vernal wetlands are indicated with pale fill, nitrogen sampler transect is indicated withthick black line. Highway 12 is located to the west of Bouverie Preserve, from upper-left tolower-middle of this map.

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Audubon Canyon Ranch’s propertiesare home to unique habitats, rare

plants, and a great diversity of birds andother wildlife. Unfortunately, ACR’s landsare also home to a multiplicity of exoticplants, many of which are invasive andcan destroy natural habitat that is essen-tial for native flora and fauna to survive.Because of this, the Habitat Protectionand Restoration (HPR) program includesan active invasive species managementplan that protects biodiversity. Naturalresource mapping plays an important rolein this plan and the success of our habitatrestoration work.

Mapping involves the collection andpresentation of spatial information, suchas the occurrence of important habitatfeatures and the distributions of invasiveplant populations. This can be done byhand drawing infestations to create maps,or by using a Global Positioning System(GPS) to more precisely collect spatialinformation. At ACR we use both meth-ods, but emphasize the use of GPS alongwith the WIMS database (see textbox).This allows us to easily transfer and

manipulate our data in standardized geo-graphic information systems such asArcGIS. With these digital tools, we cangraphically project data onto aerial pho-tos and topographic maps that can beanalyzed and shared within ACR and withour partners and used to develop effectiveplans for eradicating or managing inva-sive species, protecting rare plants, orrestoring critical habitats.

Effective protection of ACR sanctuariesoften requires that staff experiment withnovel approaches, and that we communi-cate and share insights with other landmanagers and ecological professionals.For this reason, our habitat protectionwork takes place within an adaptive man-agement framework and emphasizes acollaborative approach to managing ourproperties.

Adaptive ManagementLand managers use adaptive manage-

ment to continually revise their methodsto develop the most effective strategiesfor managing properties. Adaptive man-agement planning recognizes that uncer-

tainty is inherent in the management ofcomplex ecological systems, frames man-agement actions as experiments, andenables the planner to use the results ofmanagement experiments to inform andimprove future actions. A vital compo-nent of this approach is developing andimplementing a system of mapping.

One of the first steps in adaptive man-agement of invasive plants is to identifyspecies that threaten restoration goals. Animportant goal of the HPR Project Leaderis to map the invasive species on AudubonCanyon Ranch properties. Mapping givesus a visual picture of which habitats arethreatened by invasive species. This allowsus to prioritize restoration efforts accord-ing to the degree of threat to native habi-tats and to determine which infestationsrequire immediate attention. For example,we use maps of the Bolinas LagoonPreserve to identify the locations of themost invasive species, such as Ehrharta(Ehrharta erecta), French broom (Genistamonspessulana), Oxalis (Oxalispescaprae), and Cape ivy (Delairea odor-ata) (Figure 1). These mapping data areused in combination with impact assess-ments such as the Cal-IPC Invasive PlantInventory (http://cal-ipc.org) to prioritizetarget populations and create an effectivemanagement plan for the preservation ofour native ecosystems.

Once we have identified and priori-tized invasive plant occurrences, we canuse the information gained from map-ping, along with relevant biologicalinformation, to determine which controltechniques are appropriate for differenthabitats and infestations and plan atimeline for treatment and monitoring. Itis important to consider not only thepresence of invasive species in an area,but also numerous other special consid-erations, including the extent and den-sity of infestation, phenology of species,proximity to water, abundance of nativespecies, presence of rare or threatenedspecies, scientific or other land manage-ment uses, and presence of nesting birdsor other wildlife.

The importance of mapping in the protection and restoration of native

ecosystems

Charting the Course by Jennifer Jordan

Figure 1. High priority invasive plant species at the Bolinas Lagoon Preserve.

PartnershipsThe success of ACR’s habitat restora-

tion work results not only from an adap-tive management approach, but alsofrom a large network of professionalpartners, neighboring private landown-ers, and volunteer stewards. Mappingplays a vital role in planning and coordi-nating management actions with all ofour partners. Together with professionalpartners in the Marin Sonoma WeedManagement Area, we have mapped themost invasive species in the vicinity ofthe Bolinas Lagoon Preserve and haveobtained grant funding for a project thatwill remove these invaders from a multi-jurisdictional area of important naturalhabitat.

Accurate maps of invasive plant pop-ulations are also important tools whenworking with volunteer stewards. Mapsare necessary for planning volunteerworkdays as well as establishing perma-nent records for future reference of workperformed by some ACR volunteers whohave assumed ongoing responsibility forstewardship of specific habitats, sites, orspecies (Figure 3).

ACR continues to incorporate GIS andother mapping technologies as funda-mental tools for conservation scienceand habitat protection. With the infor-mation that mapping provides we areable to work within and beyond the bor-ders of ACR and address the invasionsthat unless controlled will continue tocreate management concerns.


Bouverie Preserve’s Lower Field is oneexample of the importance of includingseveral of the parameters listed above ona single map when developing an adap-tive management plan (Figure 2). TheLower Field grassland is a complexecosystem with a diversity of interestingnative plants and an equally diverse andinteresting invasive plant flora.Maintenance of native plant diversity atthis site requires prescribed cattle graz-ing to reduce the biomass of highly com-petitive European annual grasses. Toplan for this, we mapped invasive plantoccurrences (Taeniatherum caput-medusae), rare plant occurrences(Downingia pusilla), sensitive wetlands,and experimental grazing exclusionareas. Viewing these resources togetheron a single map was instrumental indetermining the fencing configurationthat best divided the pasture and maxi-mized our control of the timing andintensity of grazing.

Perhaps the most critical step in theadaptive management cycle is monitor-ing and assessing the outcomes of man-agement actions. We track several indi-cators of effectiveness, such as popula-tion density and size, and display themon maps in order to make intuitiveassessments. A comparison of multipleassessments made periodically (e.g.,annual intervals) allows us to monitorthe spread or abatement of infestationsand the effectiveness of our treatments.With this information we can modifymanagement plans as necessary.

Figure 2. Bouverie Lower Field, showing invasive plants (medusahead, Taeniatherumcaput-medusae), experimental areas, wetlands, and rare plants (Downingia pusilla).

Weed InformationManagement System(WIMS)

Audubon Canyon Ranch’s HabitatProtection and Restoration programhas adopted a standardized databasedeveloped by The NatureConservancy called the WeedInformation Management System(WIMS). The database enhancesACR’s ability to inventory and trackinvasive plant populations. Otheragencies in the San Francisco Bayarea and beyond are also beginningto adopt the WIMS database to inte-grate into their programs. This col-lective effort will enable resourcemanagers from many organizationsand agencies to share standardizeddata so that large scale collaborationefforts to control invasive plants willbe possible.

WIMS enables ACR to recordoccurrences of every exotic plantinfestation that we find and thenorganizes this information into arelational database. The WIMS data-base allows us to return to the samelocations to create additional assess-ments, review treatments used fordifferent populations, and record thenumber of person hours spent. Bykeeping track of this information weare able to determine which controlmethods are most effective andwhich methods should be modified.

Figure 3. VolunteerLen Blumin’s hand-drawn map of thecape ivy projectarea in BolinasLagoon Preserve’sVolunteer Canyon.

Visiting investigators


amount of nitrogen deposited on oppo-site sides of the highway. Our plan is tosample seasonal and annual nitrogendeposition.

If this pilot study indicates that deposi-tion rates are sufficient to have ecologicalimpacts, then we may initiate additionalstudies to assess the ecological effects ofnitrogen deposition on these wetlands.Additional studies may include samplingvegetation biomass at different distancesfrom the highway, with the intent of cor-relating plant growth with proximity tonitrogen sources. This relationship couldbe even more strongly substantiated byanalyzing the ratios of nitrogen isotopesin plants along the highway distance gra-dient. Automobile-generated nitrogencompounds have a characteristic isotopic“signature” that can tell us the degree towhich plants are incorporating highwaynitrogen. Finally, we would like to use“phytometers” (greenhouse-raised plantsplaced in pots in the field) to better assessecological effects of nitrogen deposition.Single-species pots could tell us how dis-tance from the highway nitrogen sourceaffects growth of individual species, andpots with multiple species could tell ushow deposition alters competitive inter-actions among species of concern.

Research demonstrating eutrophica-tion due to nitrogen deposition is a mean-ingful scientific contribution to the con-servation biology of vernal pools in itself.Equally important, however, is the appli-cation of this work to restoration ofBouverie’s vernal pools. If significant,results may be used to calibrate grazing orburning prescriptions specifically toremove the excess nitrogen deposited byvehicles. The results may also be relevantto CalTrans’ upcoming widening ofHighway 12, which is expected to increasevehicle volume and speed leading to anincrease in nitrogen deposition. Theseincreases are easily calculated and theresults could provide evidence that achange in traffic would affect adjacentecosystems. Research conducted by StuartWeiss in serpentine grasslands predictedthat widening Highway 280 would resultin quantifiable impacts; this led to mitiga-tion funding by the Santa Clara ValleyTransportation Authority for habitat pro-tection along the expansion corridor

As we wait for the first set of samplesto be processed it remains unknownwhether Sonoma Valley’s few remainingvernal pools are being harmed by vehicu-lar nitrogen deposition. However, we areconfronted by the fact that Bouverie’s ver-nal pools currently support large popula-tions of invasive plants, instead of the rarevernal pool species that thrived for thou-

sands of generations before humansaltered this area. Before we undertakeprojects to restore and reintroduceendangered vernal pool plants, we mustfirst discover the root cause behind biodi-versity loss. Ultimately, this type ofresearch is critical if conservation andrestoration efforts are to move beyond the“triage” mode of addressing symptomswithout knowing the root causes. Ourresponsibility is to protect the naturaldiversity that remains in these systems, toenhance existing populations and todream about restoring species that havebeen lost. Through careful study we hopeto ensure that nature can persist in ahuman-dominated world, inches from15,000 catalytic converters moving 65miles per hour.

References citedFenn, M.E. J.S. Baron, E.B. Allen, H. M. Rueth, K.R.

Nydick, L. Geiser, W.D. Bowman, J. O. Sickman,T.Meixner, and D. W. Johnson. 2003. Ecologicaleffects of nitrogen deposition in the western UnitedStates. BioScience 53:404-420.

Gluesenkamp, D.A. 2005. Stewardship ethic. 2005Ardeid. Audubon Canyon Ranch.

NRC (National Research Council). 1999. Perspectiveson biodiversity: valuing its role in an everchangingworld. National Academy Press, Washington, DC.129 p.

Vitousek, P.M., J. D. Aber, R. W. Howarth, G. E. Likens,P. A. Matson, D. W. Schindler, W. H. Schlesinger andD. G. Tilman. 1997. Human alteration of the globalnitrogen cycle: sources and consequences.Ecological Applications 7:737-750.

Weiss, S.B. 1999. Cars, cows, and checkerspot butter-flies: nitrogen deposition and management of nutri-ent-poor grasslands for a threatened species.Conservation Biology 13:1476-1486.

Nitrogen, from page 9

Effects of invasive species on nitrogenretention and other issues in the ecologyand restoration of coastal prairie. JeffCorbin and Carla d’Antonio, UC Berkeley.

Practical restoration tools to increasenative grass establishment in invadedhabitats. Jeff Corbin, UC Berkeley.

Ecological indicators in West Coastestuaries. Steven Morgan, SusanAnderson, and others, UC Davis BodegaMarine Lab, UC Santa Barbara.

Long-term monitoring of the Giacominiwetland. Lorraine Parsons, Point ReyesNational Seashore.

Analysis of sedimentation in natural andrestored marshes. Lorraine Parsons, PointReyes National Seashore.

Factors causing summer mortality inPacific oysters. Fred Griffin, UC DavisBodega Marine Lab.

A comparison of carbon cycling andmaterial exchange in grasslandsdominated by native and exotic grasses innorthern California. Laurie Koteen, UCBerkeley.

Black Brant counts at Drakes Estero,Tomales Bay and Bodega Bay. Rod Hug,Santa Rosa, CA.

Strophariaceae of California. Peter Werner,Dennis Desjardin, San Francisco StateUniversity.

Bouverie Preserve amphibian study. DavidCook, Santa Rosa, CA.

Surface water ambient monitoringprogram: south coastal Marin and SanFrancisco surface water quality study.Karen Taberski, San Francisco RegionalWater Quality Control Board.

Tomales Bay harbor seal monitoring. MaryEllen King, Santa Rosa, CA..

Effects of landscape context andrecreational use on carnivores in northernCalifornia. Sara Reed, UC Berkeley.

Effects of macroalgal bloom on seagrassbed productivity in Tomales Bay. BrittanyHuffington, San Francisco State University.

Impact of an introduced plant pathogen onLyme disease ecology. Cheryl Briggs andAndrew Swei, UC Berkeley.

Utility of riparian corridors to nativeCalifornia passerines. Jodi Hilty and KatieMeiklejohn, Wildlife Conservation Societyand Columbia University, respectively.

California Rapid Assessment Method —wetland assessment calibration. LetitiaGrenier and Sarah Pearce, San FranciscoEstuary Institute.

Picher Canyon Heron andEgret Project ◗ The fates ofall nesting attempts at ACR’sPicher Canyon heronry havebeen monitored annually since1967 to track long-termvariation in nesting behaviorand reproduction.

Tomales Bay ShorebirdProject ◗ Since 1989, wehave conducted annual shore-bird censuses on Tomales Bay.Each census involves six bay-wide winter counts and onebaywide count each in Augustand April migration periods. Ateam of 15–20 volunteer fieldobservers is needed to conducteach count. The data are usedto investigate winter populationpatterns of shorebirds, localhabitat values, and conserva-tion implications.

Tomales Bay WaterbirdSurvey ◗ Since 1989-90,teams of 12–15 observershave conducted winter water-bird censuses from surveyboats on Tomales Bay. Theresults provide information onhabitat values and conservationneeds of 51 species, totalingup to 25,000 birds. Futurework will focus on trends anddeterminants of waterbirdvariation on Tomales Bay.

North Bay Counties Heronand Egret Project ◗ Annualmonitoring of reproductiveactivities at all known heronand egret nesting colonies infive northern Bay Area coun-ties began in 1990. The dataare used to examine regionalpatterns of reproductive perfor-mance, disturbance, habitatuse, seasonal timing andspatial relationships amongheronries. The project hasbeen incorporated into theIntegrated Regional WetlandMonitoring (IRWM) program, aCALFED project to developregional monitoring for SanFrancisco Bay. We recentlycompleted an annotated, 250-page atlas of heronries in theSan Francisco Bay area[available online: www.egret.org].

In progress:project updates

Common Ravens inheronries ◗ We have beenobserving and radio-trackingnesting ravens in Marin Countyand measuring their predatorybehaviors in heron and egretnesting colonies. We haveproduced scientific papers onthe status of ravens and crowsin the San Francisco Bay area,on home range use, and onraven predatory behaviors.Future work will addressdiurnal movements of ravens,methods in radio telemetry,and techniques for managingraven predation.

Impacts of Wild Turkeyson forest ecosystems ◗The goal of this study is toexperimentally measure theeffects of ground foraging byinvasive, non-native WildTurkeys on vegetation, inverte-brates, and herpetofauna in theforest ecosystem of BouveriePreserve. The results willprovide information that can beused by agencies to improvemanagement and control ofturkey populations.

Monitoring and control ofnon-native crayfish ◗Jeanne Wirka and others arestudying the distribution ofnon-native signal crayfish(Pacifastucus lenisculus) inStuart Creek at BouveriePreserve and investigating theuse of barriers and traps tocontrol the potential impacts ofcrayfish on native amphibiansand other species. See articlein this issue of The Ardeid.

Terwiliger Butterfly Grove◗ ACR property near MuirBeach has supported largeconcentrations of overwinter-ing monarch butterflies.Monarchs have been absent inrecent years, but we areremoving non-native shrubsand saplings to restore thenative understory whileallowing new foliage to grow inareas that are likely to providesuitable butterfly habitat.

Highway-generatednitrogen deposition invernal wetlands ◗ DanGluesenkamp, Stuart Weiss,and Jeanne Wirka are quanti-fying the potential effects ofhighway-generated nitrogendeposition on Sonoma Valleyvernal pools. Enhanced availa-bility of nitrogen near highways

might facilitate invasion by non-native plant species and theloss of biodiversity in sensitivevernal wetlands. See article inthis issue of The Ardeid.

Cypress Point restoration◗ We are conducting a feasi-bility study for restoring theshoreline dunes at ACR’sCypress Grove Research Centeron Tomales Bay. The projectincludes options for reducingthe vulnerability of the ResearchCenter to rising sea level.

Ehrharta erecta manage-ment and research ◗Ehrharta erecta is a highlyinvasive perennial grass nativeto South Africa. We haveremoved a large patch ofEhrharta from ACR’s BolinasLagoon Preserve. A scientificproject to investigate theecological effects of Ehrhartainvasion and develop tools forthe control of Ehrharta wasdiscontinued when experi-mental plots were destroyedby flood waters.

Plant species inventory ◗Resident biologists maintaininventories of plant speciesknown to occur on ACR’sTomales Bay properties and atBouverie and Bolinas Lagoonpreserves.

Cape ivy control, VolunteerCanyon ◗ Manual removalhas proven to be very success-ful in reducing nonnative capeivy from the riparian vegetationin ACR’s Volunteer Canyon.Continued vigilance in weededareas has been important, tocombat resprouts of blacknightshade, Vinca, andJapanese hedge parsley.

Annual surveys andremoval of non-nativeSpartina and hybrids ◗ Incollaboration with the SanFrancisco Estuary InvasiveSpartina Project, Emiko Condesoand Gwen Heistand coordinateand conduct comprehensivefield surveys for invasive, non-native Spartina in the shorelinemarshes of Tomales Bay andBolinas Lagoon.

Influence of terrestrialinvertebrates ongrasslands ◗ This project willdetermine whether the domi-nance of European plantspecies in grasslands at the

Bouverie Preserve is causedby herbivory by two types ofground-dwelling invertebrates:African earwigs (Emborelliacincticollis) and Europeanslugs (Derocerius sp.).

Salt marsh ice plantremoval ◗ Native vegetationis recruiting into areas wherewe have been removing non-native ice plant from marshesand upland edges at TomsPoint on Tomales Bay.

Eradication of Elytrigiapontica spp. pontica ◗Elytrigia is an invasive, non-native perennial grass thatforms dense populations inseasonal wetland sites. AtBouverie Preserve, we areeliminating a patch of Elytrigiausing manual removal and lightstarvation/solarization (blackplastic tarps), and herbicidespot treatments to removeinvasive outlier patches.

Nest boxes ◗ Rich Stallcuphas installed and maintainsseveral Wood Duck nest boxesalong Bear Valley Creek inACR’s Olema Marsh. TonyGilbert has installed andmaintains Western Bluebirdnest boxes in the CypressGrove grasslands.

Eucalyptus removal ◗Therow of non-native eucalyptustrees was removed from thevernal wetland area alongHighway 12 at BouveriePreserve.

Restoration of coastaldunes by removal ofAmmophila arenaria ◗Ammophila arenaria is a highlyinvasive, non-native plant thatalters the topography andfunction of coastal dunes. Thisproject at ACR’s Toms Point,on Tomales Bay, is helping toprotect native species thatdepend on mobile duneecosystems.

Grazing of Bouveriegrasslands ◗ A prescribedgrazing program has beenimplemented to maintain orincrease the abundance ofnative grassland plant speciesand to protect the vernalwetlands at Bouverie Preserve.


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Monitoring nitrogen pollution see page 8

What is this device measuring? And will the information it yieldshelp ACR protect Sonoma Valley's vernal pools?

DA

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LUES

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Documents

Conservation Science and Habitat Protection at Audubon ...egret.org/pdfs/Ardeid2006.pdf2006 the ARDEID page 1 The tidal waters that illuminate the coastal landscapes of Bolinas lagoon