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Aggression in shorebirds in relation to flock density and composition
Author(s) -
METCALFE N. B.,
FURNESS R. W.
Publication year - 1987
Publication title -
ibis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 80
eISSN - 1474-919X
pISSN - 0019-1019
DOI - 10.1111/j.1474-919x.1987.tb08243.x
Subject(s) - flock , interspecific competition , aggression , intraspecific competition , flocking (texture) , ecology , biology , zoology , psychology , social psychology , materials science , composite material
The aggressive interactions of Turnstones and Purple Sandpipers feeding in wintering mixed‐species wader flocks could be classified into those involving food and those involving space. All observed interspecific encounters were of short duration and were initiated and won by the larger species; the majority did not involve food and were resolved by low‐intensity displays. Intraspecific interactions (a greater proportion of which involved food) were also resolved quickly and were usually won by the initiator. Space‐related encounters between conspecifics were more likely to be resolved than food‐related encounters just by threat displays. Aggression rates increased with flock densities. However, the increase in aggression with density was dependent on the species composition of the flock: both Turnstones and Purple Sandpipers were more likely to be involved in fights (both over food and over space) with conspecifics than with other species, indicating that the aggression costs of flocking were less in mixed‐species flocks.