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Buzzards depend upon lift for their existence. Only eating once or twice p er month, they cannot afford to expend energy on flapping their wings, so they spend time doing only one of two things: searching for food and searching for sources of lift so they can stay up and keep searching. These scavengers have very sharp eyesight-better even than hawks-with a 4,500 foot eyesight limit. Buzzards can only survive in colonies because one or two could never find enough food for survival. To conserve energy, only one leaves the roost when the sun comes up. If there's no lift, he returns to the roost, they all wait a bit, then another leaves. The birds take turns leaving until one deems the lift acceptable. At this time they all leave the nest to begin searching for food, spacing themselves 4,500 feet apart, the maximum distance they can see. When one finds food, it makes a particular motion when it turns, indicating his success, and the others come to join the feast. Buzzards will join a glider in flight, until the glider goes over 4,500 feet, at which time the birds leave because they can no longer see the ground. The only exception to this is during migration (they migrate south for the winter), when they will seek lift as high as possible to conserve energy during the long migration.
(Based on research conducted at VU by Dr. Farrar, Dean of Engineering, and another VU Professor of Biology. Dr. Farrar is a glider pilot.)
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