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Spatial structure in the diet of imperial eagles Aquila heliaca in Kazakhstan


  • Todd E. Katzner,

  • Evgeny A. Bragin,

  • Steven T. Knick,

  • Andrew T. Smith

T. E. Katzner (correspondence) and A. T. Smith, School of Life Sciences, PO Box 874501, Arizona State University, Tempe, AZ 85287-4501, USA. E.A. Bragin, Science Department, Naurzum National Nature Reserve, Kustanay Oblast, Naurzumski Raijon, Dokuchaevka, 459730, KAZAKHSTAN. S. T. Knick, USGS Forest and Rangeland Ecosystem Science Center, Snake River Field Station, 970 Lusk St., Boise, ID 83706, USA. Present address of T. Katzner: Department of Conservation and Field Research, National Aviary, Allegheny Commons West, Pittsburgh, PA 15212-5248. E-mail:


We evaluated the relationship between spatial variability in prey and food habits of eastern imperial eagles Aquila heliaca at a 90,000 ha national nature reserve in north-central Kazakhstan. Eagle diet varied greatly within the population and the spatial structure of eagle diet within the population varied according to the scale of measurement. Patterns in dietary response were inconsistent with expectations if either ontogenetic imprinting or competition determined diet choice, but they met expectations if functional response determined diet. Eagles nesting near a high-density prey resource used that resource almost exclusively. In contrast, in locations with no single high-density prey species, eagles' diet was more diverse. Our results demonstrate that spatial structuring of diet of vertebrate predators can provide important insight into the mechanisms that drive dietary decisions.