Ardea
Official journal of the Netherlands Ornithologists' Union

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Trnka A. & Prokop P. (2006) Do predators cause a change in passerine movement patterns as indicated by mist-net trapping rates? ARDEA 94 (1): 71-76
Predation can act as a selective pressure on birds, and birds may be expected to change habitat use in the presence of predators. To examine this, experiments were performed using Marsh Harrier Circus aeruginosus silhouettes. The effect of predators on movement patterns and mist nets capture efficiency were investigated in two unfamiliar passerines, Reed Warblers Acrocephalus scirpaceus and Tree Sparrows Passer montanus in natural reed beds and bushes, respectively. Birds were trapped at the end of the nesting period in eight study plots with separately placed silhouettes of raptors. We found that the presence of a predator was an important factor for capture rates in Tree Sparrows, and raptor presence affected the vertical spatial distribution of Reed Warblers in reed beds. Differences in movement patterns reflect different responses to aerial predators in these species. They may be speciesí specific or dependent on habitat type, or both. These results, therefore, point to a strong possibility that aerial predators can affect capture rates and movement patterns in studies using mist nets.


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