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Spacing and foraging behaviour of black-headed gulls Larus ridibundus in an estuary
Curtis, D.J.; Thompson, D.B.A. (1985). Spacing and foraging behaviour of black-headed gulls Larus ridibundus in an estuary. Ornis Scandinavica 16(4): 245-252
In: Ornis Scandinavica. Munksgaard: Copenhagen. ISSN 0030-5693, more
Peer reviewed article  

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Keywords
    Nereis diversicolor Müller, 1776 [WoRMS]; Marine

Authors  Top 
  • Curtis, D.J.
  • Thompson, D.B.A.

Abstract
    Black-headed gulls foraged for two prey species in an estuary using 'crouching' and 'upright' feeding techniques. Crouching gulls occurred in compact conspecific feeding associations along the tide line; upright gulls were scattered on exposed mud. Crouching gulls took more of the energetically profitable polychaete worm Nereis diversicolor, capturing most when feeding at high densities on the flow (incoming) tide. Capture rate of N. diversicolor was highest, and of the the amphipod Corophium volutator was lowest, when gulls foraged at high densities. Over 1 month density of N. diversicolor decreased by almost 30% attributed to predation by gulls. Tidal movements over the mid-shore, rather than individual differences, determined feeding technique, which in turn determined prey selection and capture rate. Factors affecting the relationship between feeding rate and bird density, such as prey depletion, disturbance and search patch restriction, are discussed.-from Authors

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