[obol] Re: Killdeer nest
- From: David Irons <llsdirons@xxxxxxx>
- To: DJ Lauten and KACastelein <deweysage@xxxxxxxxxxxx>, OBOL Oregon Birders Online <obol@xxxxxxxxxxxxx>
- Date: Thu, 17 Apr 2014 16:51:05 +0000
As Dave Lauten suggests, natural selection (the mechanism that drives the way
species evolve) is a powerful force. The strategies that work are those that
persist. Clearly, the nest site selections that Killdeer make are yielding
enough reproductive success to sustain a thriving population, thus the strategy
can be viewed as successful.
All too often, we apply a human yardstick when considering the reproductive
activities of birds and other animals, which drives most of our "wonder why?"
questions. Humans generally have one baby at a time, in part because our infant
mortality rate is extremely low when you compare it to the hatch-year mortality
of birds. In order to sustain their populations, birds must lay multiple eggs
and, in some cases, multiple clutches every single breeding season. Many eggs
never hatch, as they are eaten by snakes, skunks, raccoons, and even other
birds. When eggs do hatch, the nestlings continue to face a litany of perils
until they fledge and becoming self sufficient. Even after young birds are out
of the nest and independent, they continue to face dangers from predators and a
variety of human factors, especially those species that make long migrations in
their first six months of life.
All of the losses are part of the big evolutionary equation that is expressed
in, among other things, nest site selection, egg camouflage, clutch size,
cryptic juvenile plumages, and even the distraction behaviors of adults (i.e.
the 'broken wing' behavior of Killdeer). Like some other ground-nesting birds
(quail, grouse, shorebirds and ducks), Killdeer chicks are precocial, which
means they can walk and run almost immediately after hatching. Once they hatch,
the adults lead them away from the nest. Once away from the nest, the chicks
instinctively run and scatter and then hide in deeper grass any time one of the
adults sounds the alarm–a loud sharp single note. They don't run towards the
adult. They usually run away, with the adult acting as the decoy for the
potential threat.
If you watch closely, you'll notice that there is little wasted motion in the
life of a bird. They don't have leisure time. They don't watch TV, play video
games, read books, or engage in or watch ports contests to fill out their day.
All of their activities have a purpose that serves an instinctual drive to
survive and reproduce. Coming to appreciate the struggle that birds face and
their resiliency in response to it, fuels my fascination.
Dave Irons
Portland, OR
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