Katzner used a Global Positioning Satellite receiver to determine the exact geographic location of each nest, then analyzed their distribution with a computer. He found that each species of eagle adapted to the space limitations in different ways. Imperial eagles space themselves at very regular intervals. White-tailed sea eagles probably respond to one another, but they seem more willing to clump into groups. Katzner analyzed eagle pellets to find out what the birds were eating.
Birds of prey eat animals whole.
The regurgitated material consists of hard oval pellets, each about two to four inches in length. During his summers in Kazakstan, Katzner analyzed more than 3,000 eagle pellets. He collected the pellets near nests or under large roosting trees. Eagles eat almost any kind of small animal. Katzner's subjects appear to have narrowed their choices.