Waterbirds and Human Disturbance IN URBANized Areas

John TakekawaUSGS Western Ecological Research Center

Vallejo, California

Jules EvensAvocet Research Associates

Point Reyes Station, California

Kevin LaffertyUSGS Western Ecological Research Center

Santa Barbara, California

Disturbance

Species Composition

ActivityHarvest

Habitat Modification

Pollution1. Causes of Impact

2. Immediate Response

3. Long-term Effects on:

a. Individuals

c. Communities

b. Populations

BehaviorChange

Death

AlteredBehavior

DeathAltered

VigorAltered

Productivity

Abundance DemographicsDistribution

Interactions

Size correlation: larger birds are less tolerant of human disturbance than smaller ones (Rodgers and Schwikert 2003, Fernandez-Juricic et al. 2002)

Larger flocks flush at greater distances than smaller flocks or individuals.

Flight distance correlated positively with flock size and species diversity. Flight distances longer for species that used open water for foraging than for resting (Mori et al. 2003, ARA 2008)

To compensate for increased disturbance, birds may increase food intake or relocate to less profitable areas to feed.

Size of area available: the larger the habitat patch, the shorter the distance of flight response, the lower the disturbance.

Proximity of refuge.

The “shyness” of the species (Scaup versus Ring-billed Gull)

Size of the species (a black rail allows closer approach than a heron)

Season: periods of high-energy costs exact more “expensive” responses.

Flight distances are longer for waterfowl that used an area for foraging than for resting (Mori et al. 2001)

Solitary nesting birds

Colonial nesting birds

Flocking shorebirds

Rafting waterbirds

More sensitive than roosting and foraging birds

Response depends on site, colony size, species and time of year.

Recommended buffer

zones around colonies range from 100 m (Rodgers and Smith 1995), to 300 m (Butler 1992), recommended by JE (Jan-Sep).

Tidal flat specialists

Peak numbers occur during migratory pulses in fall and winter, but large numbers of overwinter; a few species nest.

Foraging shorebirds somewhat protected from watercraft on tidal flats or in very shallow (<10 cm) water. However, high tide roosts are susceptible to disturbance (Burger and Gochfield 1991, Davidson 1993, Kelly 1997).

Majority occur in SFB during “winter” (Oct-Apr).

Divers on open water, dabblers on seasonal wetlands.

Divers gather in large flocks (rafts) concentrated at the mouths of tributaries, bays and coves.

Scaup and scoters combined comprised 87 percent of waterfowl on open water.

Large flocks of scaup, scoter and others key on herring spawn in eelgrass beds (Zostera marina)

Mid-winter aerial surveys from 1970-1991 averaged 425,000 waterfowl present in mid-Feb.

Mid-winter waterfowl surveys 1992-2007 (exclusive of 1996) averaged 182,818 birds present in mid-Jan.

Numbers of waterfowl decreased 25% from the 1950s until 1990 (Takekawa et al. 2000).

Waterfowl continue their downward trend from 300,000 in the late 1980s (Accurso 1992) to 184,160 (SE±65,670) from 1992-2007.

Table 11. Mean and standard deviation (SD) of ln-transformed disturbance response distances, back-transformed mean response distance, and recommended distances (m) to avoid disturbance of waterbird, based on species behavioral responses to 1 or 2 approaching kayaks.

Species n trials Meana SDa

Mean response distance

(m)b Flock sizec

Recommended distance

(m)d

American Coot 28 3.18 0.621 24 107 Bufflehead 51 4.06 0.556 58 1 92 50 174 Canada Goose 19 3.99 0.602 54 186 Clark's Grebe 23 3.72 0.668 41 1 78 12 202 Com. Goldeneye 24 3.62 0.724 37 163 Common Loon 16 3.93 0.756 51 218 Double-crested Cormorant 23 4.11 0.628 61 213 Greater Scaup 31 4.59 0.433 99 1 127 120 246 Horned Grebe 37 3.17 0.779 24 126 Lesser Scaup 16 3.94 0.699 51 1 86 8 252 Mallard 19 2.87 0.534 18 83 Red-br. Merganser 13 3.32 1.136 28 219 Ruddy Duck 56 4.10 0.623 60 209 Scaup species 30 4.54 0.549 94 1 141 100 218 Surf Scoter 37 4.11 0.762 61 1 97 25 e 153 Western Grebe 30 3.68 0.649 40 156

` a Mean and standard deviation of log-transformed data: yi = ln(xi) bBack-transformed mean: ^ = exp(yų ) cIf the linear effect of species flock size on disturbance response was significant (P < 0.05), the regression equation was used to calculate recommended distance for solitary individuals (Flock size = 1) and maximum observed floc k size (Flock size > 1):

Bufflehead: y = 3.81 + 0.017*(Flock size) - 0.0012*(Intraseasonal day) Clark's Grebe: y = 3.08 + 0.110*(Flock size) + 0.002*(Intraseasonal day) Greater Scaup: y = 4.16 + 0.007*(Flock size) + 0.002*(Intraseasonal day) Lesser Scaup: y = 3.17 + 0.194*(Flock size) + 0.001*(Intraseasonal day) Scaup species: y = 4.16 + 0.004*(Flock size) + 0.003*(Intraseasonal day) Surf Scoter: y = 3.64 + 0.024*(Flock size) + 0.003*(Intraseasonal day)

d Recommended distance = exp ( ^ + 1.6495 * ^) + 40 m. e Outlier observations for Surf Scoters flocks of 70 and 35 occurred but the remainder of the Surf Scoter flocks observed during trials were less than 25 individuals.

N =74

Earliest (most distant) response: 52% swimming 31% diving 16% flight

ANOVA to examine differences in species disturbance responses between number of kayaks (1 vs. 2 or 3), tide level, year, weekday s weekend, and transect area (depth)

No significant differences were found in species responses related to the main effects of year, tide level, transect area, weekday vs. weekend, or number of kayaks (P > 0.05)

Species buffer zones based on observed flush distances (mean plus one SD, after Rodgers and Schwikert 2003)

Add 40 m to buffer to minimize agnostic responses and to account for mixed species (Thompson and Thompson 1985, Gutzwiller et al. 1998).

Buffer zones should be based on the species most sensitive to disturbance (scaup)

“One size fits all” approach for management: “therefore a buffer

zone of 250 meters from areas of high-use by rafting waterbirds as a quideline for minimizing the impacts of non-motorized watercraft on rafting waterbirds.”

SFB FERRIES

Resource Concerns:Open Water DisturbanceDisplacement EffectsHabitat Erosion

1. Conduct ferry surveys in San Francisco Bay to assess species-specific buffer distances.

2. Examine waterbird avoidance of watercraft in land-based surveys at selected areas.

3. Document distribution of waterbirds along ferry routes with aerial surveys.

Distance?

Distance?

Flight Response

Diving Response

ScaupNV=not visible, ND=not disturbed, A=alert,

SA=swim away, DI=dive, FL=fly

0 100 200 300 400

FL

DI

SA

A

ND

NV

Disturbance Behavior

Average Distance (meters)

ScoterNV=not visible, ND=not disturbed, A=alert,

SA=swim away, DI=dive, FL=fly

0 200 400 600 800

FL

DI

SA

A

ND

NV

DisturbanceBehavior

Average Distance (meters)

GrebesNV=not visible, ND=not disturbed, A= alert,

SA= swim away, DI=dive, FL=fly

0 100 200 300 400

FL

DI

SA

A

ND

NV

Disturbance Behavior

Average Distance (meters)

Photo Ann Cook

Distance?

Distance?

Elapsed Time?

Counts of Birds After Ferry Passage1/19/2005

0

5

10

15

20

25

30

35

40

-10 0 10 20

SP

SS

DivingDuck

WCR

Grebe

ParadiseBeach PierTotal

Time since last ferry, minutes

Total Number By Site After Ferry Passage

0

20

40

60

80

100

120

140

-50 0 50 100

Time since last ferry, categorized (minutes)

Nu

mb

er

Alameda Terminal

Bay Farm Terminal

Larkspur Terminal

Oakland Terminal

Point Orient

Point Pinole Pier

Sandy Beach Road

Sausalito Terminal

Shoreline Park, Oakland

Tiburon Terminal

Vallejo Terminal

Grand Total

Coal Oil Point ReserveCoal Oil Point ReserveUniversity of CaliforniaUniversity of CaliforniaNatural Reserve SystemNatural Reserve System

-Up to 150 wintering snowy plovers-No successful breeding for 30 years-Uncontrolled public access-No previous plover management

Lafferty, K. D. 2001. Birds at a Southern California beach: seasonality, habitat use Lafferty, K. D. 2001. Birds at a Southern California beach: seasonality, habitat use and disturbance by human activity. Biodiversity and Conservation 10:1949-1962.and disturbance by human activity. Biodiversity and Conservation 10:1949-1962.Lafferty, K. D. 2001. Disturbance to wintering western snowy plovers. Biological Lafferty, K. D. 2001. Disturbance to wintering western snowy plovers. Biological Conservation 101:315-325.Conservation 101:315-325.Lafferty, K. D., D. Goodman, and C. P. Sandoval. 2006. Restoration of breeding by Lafferty, K. D., D. Goodman, and C. P. Sandoval. 2006. Restoration of breeding by snowy plovers following protection from disturbance. Biodiversity and Conservation snowy plovers following protection from disturbance. Biodiversity and Conservation 15:2217-2230.15:2217-2230.

Initiate applied researchInitiate applied research• Why study disturbance?• Project goals

– Sources of disturbance– Rates of disturbance– Management model

Who uses the beach?

72% are students 7 visits / mo. for 2 yrs

Lack of Awareness 98% could not identify

a snowy plover 67% did not know the

area was a reserve

• What do they do?• 85% walk• 68% jog

• 46% sunbathe• 38% surf• 21% watch sunset• 20% party• 15% beach cleanup• 14% dog walk• 13% bird watch• 12% painting• 12% ride horses

How much disturbance does each plover experience?

Weekday: every 43 min. Weekend: every 27 min.

16 times higher than at protected beaches

Assess plover sensitivity

Examine disturbance with distance

Model habitat need

•Close delta trail•Rope roost area

•Place signs•Initiate a docent program

Undertake management actions

Erect rope fence: winterErect rope fence: winter

•EducationEducation•Compliance (leash law, trespass)Compliance (leash law, trespass)•Scare crows from nestsScare crows from nests

Initiate docent program

Create increased awareness

0

10

20

30

40

50

60

70

80

90

100

Wintering Breeding Wintering Breeding Wintering Breeding

2000 2001 2002

% o

f pu

blic

that

iden

tifi

ed p

love

rs Before management After docentsAfter signs

Increase compliance

0

1

2

3

4

5

6

Wintering Breeding Wintering Breeding Wintering Breeding

2000 2001 2002

Unl

eash

ed d

ogs/

hr

0

10

20

30

40

50

60

70

80

% le

ashe

d do

gs

unleashed dogs/hr

% leashed

Before management After management

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Win

teri

ng

Bre

edin

g

Win

teri

ng

Bre

edin

g

Win

teri

ng

Bre

edin

g

Win

teri

ng

Bre

edin

g

Win

teri

ng

Bre

edin

g

1999 2000 2001 2002 2003 2004

Time

Dis

turb

ance

s pe

r pl

over

/hr run/move fly

before protection during protection

Reduce disturbance

Year Pairs Nests Chicks Fledged

1970-2000 few 0-2 0

2001 1 1 1

2002 5 9 14

2003 12 24 40

2004 14 51 29

2005 30 64 30

2006 34 43 48

Recover breeding population

How do we measure non-lethal costs of disturbance and weigh those at the population level?

The effects of disturbance may be primarily behavioral rather than numerical; do multiple regression studies designed to examine the effects of independent variables measure disturbance effectively?

Site specific habitat elements may override expected responses by waterbirds: How do we identify which sites are peculiar and which are normal.

How does habituation factor in and what are the costs to reproductive fitness?

What would be the habitat values if background disturbance didn’t eliminate larger and more sensitive species?