Songbirds as Biosentinels for Songbirds as Biosentinels for Tidal WetlandsTidal Wetlands

Initial results from North and South San Francisco Initial results from North and South San Francisco BayBay

Letitia Grenier, Josh Collins, Jen Hunt, Shira Letitia Grenier, Josh Collins, Jen Hunt, Shira Bezalel, and April RobinsonBezalel, and April Robinson

San Francisco Estuary InstituteSan Francisco Estuary Institute

RoyceLaTourrette

LaTourrette

Problem StatementProblem Statement

Mercury bioaccumulation problem in the Mercury bioaccumulation problem in the EstuaryEstuary

Tidal wetlands restoration on large scaleTidal wetlands restoration on large scale Restoration provides tremendous benefits Restoration provides tremendous benefits

for wildlifefor wildlife Concern that increased mercury in the Concern that increased mercury in the

food web a possible side effectfood web a possible side effect

Sentinel Species ApproachSentinel Species Approach

Direct measurement of Hg problemDirect measurement of Hg problem MethylmercuryMethylmercury Food web = wildlife, peopleFood web = wildlife, people

Integrate over appropriate spatial Integrate over appropriate spatial and temporal scalesand temporal scales

Link to water/sediment processesLink to water/sediment processes

Uses of Sentinel SpeciesUses of Sentinel Species

Identify areas where mercury Identify areas where mercury bioaccumulation is a problembioaccumulation is a problem HabitatsHabitats Areas slated for management actionsAreas slated for management actions

Track change in food web mercury Track change in food web mercury over timeover time

Each sentinel species is specific Each sentinel species is specific to one habitatto one habitat

Year-round residentsYear-round residents Small home rangeSmall home range Abundant Abundant Important role in food webImportant role in food web

Habitat-based Hg Habitat-based Hg MonitoringMonitoring

Peter LaTourrette

13C

-24 -22 -20 -18 -16 -14

15 N

10

11

12

13

14

15

16

17

Sparrow

Goby

Marsh Plain Foods

Low Marsh Foods

Tidal Channel Foods

cordgrassgum plant

pickleweed

SLOUGH

MARSH PLAINLOW

MARSH

cordgrassgum plant

pickleweed

SLOUGH

MARSH PLAINLOW

MARSH

Grenier 2004

Habitat-specific Sentinel Habitat-specific Sentinel SpeciesSpecies

Salt PondTidal Marsh

Comparisons within a Comparisons within a SpeciesSpecies

beforeafter

Tidal Marsh Song Tidal Marsh Song SparrowsSparrows

salt marshbrackish marsh

salt marsh

samuelismaxillaris

pusillula

San Pablo Bay

Suisun Bay

San Francisco Bay

Marshall and Dedrick 1994

Upland and Tidal MarshUpland and Tidal Marsh

gouldiigouldiiuplandupland

maxillarismaxillarisbrackish marshbrackish marsh

Iron sulfide

Mineral Research Co.

Iron oxideIconofile

Grenier and Greenberg 2005

Continent-wide Data Set

Tidal Marsh Sparrows

Petaluma

GuadalupeAlviso

Tidal marsh Tidal marsh songbirdssongbirds

5 locations5 locations

September 2006September 2006

Mercury in blood Mercury in blood (wet weight)(wet weight)

Bird Blood Higher than Fish Bird Blood Higher than Fish Tissue Relative to Trophic Tissue Relative to Trophic

LevelLevel Sparrow Sparrow (median 0.31 ug/g ww, n = 37)(median 0.31 ug/g ww, n = 37) ~ 6x ~ 6x

small fish mean small fish mean (RMP 2005 data)(RMP 2005 data), despite , despite both being secondary consumersboth being secondary consumers

Yellowthroat Yellowthroat (median 0.42 ug/g ww, n = 4)(median 0.42 ug/g ww, n = 4) ~= striped bass ~= striped bass (RMP 2003 data)(RMP 2003 data)

Wren Wren (0.82 ug/g ww, n = 1)(0.82 ug/g ww, n = 1) ~ leopard ~ leopard shark median shark median (RMP 2003 data)(RMP 2003 data)

Mercury Varied by Mercury Varied by SpeciesSpecies

Blo

od H

g ug

/g w

w

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Sparrow Swallow Wren Yellowthroat

Marsh Plain: aerial insect and spider food chain

Marsh Plain: more epibenthic food chain

(transient)

South Bay data

Higher Hg in North Bay Higher Hg in North Bay MarshesMarshes

Song Sparrow

Unpublished data provided by Darell Slotton

Combined Combined FMP and RMP FMP and RMP datadata

Highest Highest concentratioconcentrations in South ns in South Bay fishBay fish

MississiMississippi ppi

SilversidSilversidee

Data from Darell Slotton and Ben Greenfield

Higher Variability in Higher Variability in North BayNorth Bay

Song Sparrow

HH1: 1: Elevation leads to Elevation leads to MercuryMercury

Lower, newer, subsided marshes

Higher, older marshes, with more variable elevation

ElevationElevation Proxy forProxy for

Frequency of wetting/dryingFrequency of wetting/drying TideTide GroundwaterGroundwater

Amount of organic matter Amount of organic matter (peat)(peat)

Marsh ageMarsh age

Implications of Marsh Plain Implications of Marsh Plain ElevationElevation

Affects connectivity to slough/bay Affects connectivity to slough/bay food web(?)food web(?)

Slowly increases as restored marshes Slowly increases as restored marshes ageage Need long-term monitoringNeed long-term monitoring

Ele

vati

on o

f m

ars

h p

lain

Food w

eb co

nnectiv

ityFish HgBird Hg

HH2:2:

SummarySummary Sentinel species directly measure the Sentinel species directly measure the

mercury problem at appropriate scales of mercury problem at appropriate scales of space and timespace and time

Songbirds can be used to monitor Hg in Songbirds can be used to monitor Hg in nearly every tidal marsh across the Estuary nearly every tidal marsh across the Estuary within the same specieswithin the same species

Initial songbird Hg data suggest several Initial songbird Hg data suggest several hypotheses for future studyhypotheses for future study

Next StepsNext Steps Wider regional survey of sentinel Wider regional survey of sentinel

speciesspecies Test hypotheses by Test hypotheses by

Comparing different types of marshesComparing different types of marshes Monitoring restoration projectsMonitoring restoration projects Studying diets with stable isotopesStudying diets with stable isotopes

Riparian areas, coastal fog beltRiparian areas, coastal fog belt Consider Hg effects on passerinesConsider Hg effects on passerines

AcknowledgementsAcknowledgements

Thanks to the following funding Thanks to the following funding sources: Santa Clara Valley Water sources: Santa Clara Valley Water District, State Coastal District, State Coastal Commission, San Francisco Commission, San Francisco Foundation Bay Fund, Regional Foundation Bay Fund, Regional Monitoring Program for Trace Monitoring Program for Trace Substances, San Francisco Substances, San Francisco Estuary Institute.Estuary Institute.

Scott Haefner