Transcript Template for Title Slide

John Takekawa
USGS Western Ecological Research Center
Vallejo, California
Jules Evens
Avocet Research Associates
Point Reyes Station, California
Kevin Lafferty
USGS Western Ecological Research Center
Santa Barbara, California
1. Causes of Impact
Activity
Harvest
a. Individuals
b. Populations
c. Communities
Pollution
Behavior
Change
2. Immediate Response
3. Long-term Effects on:
Habitat
Modification
Altered
Behavior
Death
Altered
Vigor
Abundance
Disturbance
Altered
Productivity
Distribution
Species
Composition
Death
Demographics
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.

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 nonmotorized watercraft on rafting waterbirds.”
SFB FERRIES
Resource Concerns:
Open Water Disturbance
Displacement Effects
Habitat 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.
Flight Response
Distance?
Distance?
Diving Response
Scaup
NV=not visible, ND=not disturbed, A=alert,
SA=swim away, DI=dive, FL=fly
NV
ND
Disturbance A
Behavior SA
DI
FL
0
100
200
300
Average Distance (meters)
400
Scoter
NV=not visible, ND=not disturbed, A=alert,
SA=swim away, DI=dive, FL=fly
NV
ND
Disturbance A
Behavior SA
DI
FL
0
200
400
600
Average Distance (meters)
800
Grebes
NV=not visible, ND=not disturbed, A= alert,
SA= swim away, DI=dive, FL=fly
Photo Ann Cook
NV
ND
Disturbance
Behavior
A
SA
DI
FL
0
100
200
300
Average Distance (meters)
400
Distance?
Distance?
All species
500
300
200
100
Distance to Ferry (meters)
700
600
500
400
300
200
100
0
0
Number
400
Elapsed Time?
Counts of Birds After Ferry Passage
1/19/2005
40
35
SP
30
25
20
SS
15
Diving
Duck
10
WCR
5
0
-10
Grebe
0
10
Time since last ferry, minutes
20
Paradise
Beach Pier
Total
Total Number By Site After Ferry Passage
Number
140
120
100
80
Alameda Terminal
Bay Farm Terminal
Larkspur Terminal
Oakland Terminal
Point Orient
60
40
20
0
-50
Point Pinole Pier
Sandy Beach Road
Sausalito Terminal
Shoreline Park, Oakland
0
50
Time since last ferry, categorized
(minutes)
100
Tiburon Terminal
Vallejo Terminal
Grand Total
Coal Oil Point Reserve
University of California
Natural Reserve System
-Up to 150 wintering snowy plovers
-No successful breeding for 30 years
-Uncontrolled public access
-No previous plover management
Initiate applied research
• Why study disturbance?
• Project goals
– Sources of disturbance
– Rates of disturbance
– Management model
Lafferty, K. D. 2001. Birds at a Southern California beach: seasonality, habitat use
and disturbance by human activity. Biodiversity and Conservation 10:1949-1962.
Lafferty, K. D. 2001. Disturbance to wintering western snowy plovers. Biological
Conservation 101:315-325.
Lafferty, K. D., D. Goodman, and C. P. Sandoval. 2006. Restoration of breeding by
snowy plovers following protection from disturbance. Biodiversity and
Conservation 15:2217-2230.

Who uses the beach?
 72% are students
• What do they do?
• 85% walk
• 68% jog
 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
•
•
•
•
•
•
•
•
•
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
Undertake management actions
•Close delta trail
•Rope roost area
•Place signs
•Initiate a docent program
Erect rope fence: winter
Initiate docent program
•Education
•Compliance (leash law, trespass)
•Scare crows from nests
Create increased awareness
% of public that identified plovers
100
90
Before management
After signs
After docents
80
70
60
50
40
30
20
10
0
Wintering
Breeding
2000
Wintering
Breeding
2001
Wintering
Breeding
2002
Increase compliance
6
80
Before management
After management
70
5
4
50
3
40
30
2
20
unleashed dogs/hr
1
10
% leashed
0
0
Wintering
Breeding
2000
Wintering
Breeding
2001
Wintering
Breeding
2002
% leashed dogs
Unleashed dogs/hr
60
Reduce disturbance
before protection
during protection
run/move
1.2
fly
1
0.8
0.6
0.4
0.2
1999
2000
2001
2002
Time
2003
Breeding
Wintering
Breeding
Wintering
Breeding
Wintering
Breeding
Breeding
Wintering
0
Wintering
Disturbances per plover/hr
1.4
2004
Recover breeding population
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

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?