Download Effects of human disturbance on waterbirds

Effects of human disturbance on waterbirds
The San Francisco Bay supports millions of
waterbirds, shorebirds, diving ducks, and
waterfowl
Recreational activities are increasing in
the Estuary
Conceptual model of disturbance impacts
Potential
Disturbance
event
No behavioral
response
Increased risk of
predation
Behavioral response
(increased vigilance,
fleeing)
Decreased
body
condition
Modified from White 2009
?
Decreased
reproductive
success
Decreased food intake
and increased energy
expenditure
Decreased
population
Need to assess potential impacts of
disturbance on waterbirds
What have other studies found?
•Searched published and unpublished literature
•Reviewed 110 studies
•Restricted analysis to 49 studies on birds that
are likely to occur in the Bay Area.
Percent of studies
Disturbance impacted birds
80
60
40
20
No impact
Impact
Change in behavior most frequently cited
effect of human disturbance
•Increasing vigilance
•Calling
•Changing daily activities
• Flushing
57% reported birds
flushing as disturbing
agent approached
Flush distance varied by species and type of
disturbance
Sanderlings flushed
at 15 m
Dabbling ducks flushed
at 50 m
Flush distance may not be indicative of
sensitivity
•Birds in good condition
may be more likely to
respond to disturbance
•Trade-off between
perceived risk of predation
and risk of starvation
Factors affecting response to disturbance
Distance from
disturbance
Body size
Distance to other
suitable foraging
or roosting areas
Frequency of
disturbance
Reaction of
conspecifics
Flock size
Number of people,
dogs, vehicles,
boats
Season
Angle of
approach
(direct or
tangential)
Modified from White 2009
Food availability
Speed
Body condition
Immediate versus population level effects
•8 studies assessed
impacts to reproduction
•8 studies reported
changes in foraging time
•3 reported energetic
consequences.
Energetic expenditure
•Five boating disturbances per day
increased energy expenditure in
Canvasbacks
•Need to consume an additional 75
kcal/day to compensate
•Disturbed Mallards lost more body
mass than undisturbed birds
•Increased by 10.5 kcal/day above the
normal for every 4 boats/hour of
disturbance
Energetic expenditure
•Energy expenditure increased 13% for
every 30 minute of alarm flights
•Increased 0.6 kcal/hour for every
hour of disturbance
Reproductive Costs
•Increased risk of nest
abandonment
•Increased risk of loss due
to exposure
•Increased risk of loss due
to predator attraction
Management recommendations
•Identify locations and times when birds may be
more sensitive to disturbance
•Route trails around sensitive areas
•Establish set-back distances (250 m)
•Seasonal closures
•Enforce leash laws
•Public education and
docent programs
Research recommendations
1. Determine population level consequences of
disturbance
2. Determine energetic costs of disturbance
3. Determine what areas should have seasonal
closures or set-back distances imposed
4. Create individual based models to help predict the
impacts of disturbance
Future Plans
• Conduct a before and after study to assess the
impacts of the water trail on diving ducks in the
bay
• Partner with USGS to identify diving duck
hotspots
• Overlay water trail sites with diving duck
hotspots
• Work with Bay Area Audubon Chapters to help
assess potential impacts
• Develop a docent and educational program