Jay Lehman's account of his birding at Mosquito brought up a question.
Last weekend up there, I and a lot of other folks watched eagle after
eagle lumber by, spooking up all the shorebirds, gulls, and terns every
time. With so many birds present you have to work methodically through
them, and a disturbance means you have to start over again. It's a
nuisance for observers, but not much more than a nuisance for the birds,
since none of the eagles paid much attention to them.
        In Ohio, many of these birds have very long journeys ahead of them, and
I assume they do not waste energy fleeing predators unless there's a
real threat. These birds can recognize one; I recall reading about
research by Tinbergen indicating that nestling gulls seem to have inborn
abilities to discriminate among avian predators as to which is a real
danger. But how many readers have ever seen a bald eagle pursue and kill
a healthy shorebird in these parts? I haven't, but maybe I've just never
been around at the right time. Many times I've seen eagles that seem to
be delighting in their ability to scatter smaller species, but never any
serious or successful pursuit of shorebirds.
        Bald eagles are indeed powerful, but in flight not really a match for
nimbler shorebirds. Many times I've watched falcons easily pluck dinner
from a shorebird flock, but never an eagle. Among other waterbirds,
falcons can zip a duck out of the air, but eagles are more likely to
successfully chase a coot on its slow take-off...if they can't find a
verrry slow-moving dead carp. That's my experience, but the shorebirds
must know better, as they and other birds like gulls and terns routinely
panic at the sight of a bald eagle.  I've also seen them panic at the
approach of a harrier, which may be a little more capable of catching
one than an eagle, but not a major predator of shorebirds. What is your
experience with red-tails? Kestrels?
        What have others observed?  Is it only the migrant shorebirds, in
unfamiliar territory with unfamiliar predators, that react in this way?
Do eagles spook flocks of killdeers? Remember that a lot of shorebirds
nest north of, and winter south of, the bald eagle's range. Have
shorebirds yet to regain familiarity with bald eagles since their
recovery from DDT poisoning? Just some food for thought. Please share
pertinent observations.
Bill Whan
Columbus

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