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Strong territoriality and weak density-dependent reproduction in Lesser Spotted Eagles Clanga pomarina

Research paper by Rimgaudas Treinys, Uǵis Bergmanis, Ülo Väli

Indexed on: 25 Jan '17Published on: 24 Jan '17Published in: Ibis



Abstract

We assessed whether populations of the migratory, philopatric, territorial Lesser Spotted Eagle Clanga pomarina are regulated through territoriality and density-dependent reproduction rates. In the north-western part of the distribution to the east of the Baltic Sea, territories were spaced regularly and consistently between years. We did not find strong support for an improvement of reproductive output with an increase in distance to the nearest neighbour or with a decrease of the number of conspecifics within a 2-km radius around nest-sites. Eagles differed greatly in territory spacing across three studied geographical areas, but breeding performance did not follow the same pattern. Performance of birds at the northern limit of their distribution did not differ from that in an adjacent southern area. Moreover, breeding performance fluctuated synchronously across different geographical areas, perhaps indicating climatic spatial autocorrelation or trophic interactions with synchronous vole population fluctuations over large areas. Our data suggest population regulation through territoriality but do not identify density-dependent breeding performance in this internationally protected raptor. Population density may be a good criterion for the selection of priority sites for conservation, but synchronous fluctuations in reproductive success over large geographical areas suggest that habitat conservation should similarly be focused at large scales.