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Conditions of Co-Existence in Sympatric Breeding Populations of Acrocephalus Warblers
Clive K. Catchpole
Journal of Animal Ecology
Vol. 42, No. 3 (Oct., 1973), pp. 623-635
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/3128
Page Count: 13
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(1) Sympatric breeding populations of the reed warbler (Acrocephalus scirpaceus) and the sedge warbler (A. schoenobaenus) have been studied at the Attenborough Nature Reserve, Nottinghamshire, since 1966. By quantitative study of spatial and temporal patterns, the multidimensional niche occupied by each species was determined, together with the resulting degrees of separation, overlap and possible conditions of competition. (2) Nest-sites of the two species were separated horizontally in different habitats, reed warblers mainly in marshland (particularly Phragmites) and sedge warblers mainly in dry land habitats close to water. Reed warbler nests were on average built twice as high above the ground as sedge warbler nests. (3) Where overlap in breeding habitats occurred, in field vegetation, the two species interacted strongly and maintained mutually exclusive territories. (4) Feeding habitats were often different from breeding habitats; reed warblers foraged mainly in willow woodland and sedge warblers mainly in Glyceria marsh. Reed warblers also tended to forage higher in vegetation than sedge warblers. (5) Some overlap occurred in feeding habitats and in prey taken, but there was considerable individual variation in relation to fluctuations of prey and local availability of foraging habitats. (6) Temporal separation was also detected, and resulted in more sedge warbler young produced in the first half of the breeding season, and more reed warbler young in the latter half. (7) The problem of co-existence is discussed in relation to the spatial and temporal separation demonstrated, to wintering ecology in Africa, and to studies on similar sympatric species. Some speculations are advanced concerning the evolution of Acrocephalus warblers and their ecology.
Journal of Animal Ecology © 1973 British Ecological Society