Bird Foraging Behaviors

All birds must employ foraging behaviors that let them do their best job possible of surviving. The basic principle has selected for a bewildering variety of foraging techniques over the entire bird world, with generalists often displaying a large number of behavior and specialists using very few. Generalists may not be particularly efficient at any single task but, being jack-of-all-trades, they can switch from one food to another as conditions change.

Bill shape and sizes --- and to some extent, feet, legs, and wings --- vary among species according to the foods the birds eat or the feeding methods they use. Imagine a cardinal, with a blunt bill, trying to probe deeply for earthworms in a forest floor; or a woodcock, with its long, slender bill, struggling to open a sunflower seed; or a Mallard attempting to glean insects from the furrowed bark of a maple tree. It is a picture of frustrated and hungry birds.

But it is a false picture, since the evolution of bird bills has proceeded in step with the evolution of bird foraging behaviors and diets. There is, however, a difference between the evolution of bill shapes and that of foraging behavior: Behavior can be much more variable than bill shape. A bird trying to adapt to different foods in different seasons or in different localities has no choice but to use the bill it was given. But it can acquire many different foraging behaviors, each suited to a particular food source or habitat. Whimbrels and Hudson Godwits, for example, can use their bills to peck at insects on arctic tundra plants during the summer, as well as probe for small invertebrates in the mud of a coastal estuary during the winter.

These pecking and probing behaviors have evolved for these situations, and each bird must learn how to probe deeply for different prey and how to follow tide lines in order to obtain the most food. To a great extent, the kinds of food available determine the feeding behaviors of birds. A particular kind of food may exist in many different situations requiring different feeding techniques, For example, many birds feed on insects, but their methods vary depending on whether the insects are found on tree bark, in tree litter, or on surface vegetation, in rotting wood, in the soil, underwater, or flying through the air.