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Keywords:

  • microtine predators;
  • distribution;
  • co-occurrences;
  • guild structure;
  • lemmings

1.  We studied the spatial distribution of avian microtine predators using data from 19 study areas on the tundra of northern Siberia.

2.  Numbers of snowy owls, and long-tailed skuas and pomarine skuas depended strongly on lemming density. However, a significant relationship between lemming density and number of rough-legged buzzards appeared first after removal of the effect of snowy owl abundance on the distribution of rough-legged buzzards.

3.  We applied a recently developed method (Manly 1995) to examine co-occurrences of species and found that rough-legged buzzards and snowy owls did not co-occur while snowy owls, long-tailed skuas and pomarine skuas did.

4.  There are large differences in nest construction and chick behaviour between rough-legged buzzards and the three other species. Moreover, the snow owl is a polyphagous predator preying also on large birds including raptor chicks. Therefore, we propose that reduced risk of nest predation favours rough-legged buzzards nesting away from snowy owls.

5.  Variations in abundance of the two lemming species did not seem to influence the distributions of snowy owls and rough-legged buzzards. Neither was it likely that latitudinally related factors such as breeding season length affected the distribution of rough-legged buzzards.