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Sea gulls and crows feed on various types of mollusks
by lifting them into the air and dropping them onto
a rock to break open their shells. Biologists have
observed that northwestern crows consistently drop
a type of mollusk called a whelk from a mean height
of about 5 meters. The crows appear to be selective;
they pick up only large-sized whelk. They are also
persistent. For instance, one crow was observed
to drop a single whelk 20 times. Scientists have
suggested that this behavior is an example of decision-making
in optimal foraging.
Why do you think crows consistently
fly to a height of about 5 meters before dropping
a whelk onto the rocks below?
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