Non-random pairing in American kestrels: mate choice versus intra-sexual competition

Animal Behaviour
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Abstract

Natural selection may influence the arrangement of individuals into mated pairs through either inter-sexual (mate choice) or intra-sexual selection (competition). A study of the American kestrel, Falco sparverius, in northern Saskatchewan distinguished between these two processes using size as a measure of the bird's competitive ability, and condition (mass scaled to body size) as an index of quality. Both sexes arrive on the study area after spring migration in equal numbers and males establish territories. Males and females that moved among territories at the time of pair formation were not different in size or condition from those that did not move, suggesting that birds were not being displaced by superior competitors, and that females moved to encounter potential mates. Within mated pairs, there was no relationship between a bird's size and the condition of its mate for either sex as would be predicted if intra-sexual competitition explained mating patterns. Instead, there was positive assortative mating by condition, suggesting that both sexes used quality as the criterion in choosing mates. There was no correlation between the sizes of males and females in mated paird. Because there were no differences in size or condition of breeding and non-breeding males, factors other than physical attributes, such as prior experience with the area, may determine a male's success in obtaining a territory. Because females that did not obtain mates were in poorer condition than those that did, males may have rejected poor quality females. The results suggest that intra-sexual competition was not important for pair formation, and that kestrels chose mates on the basis of quality.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Non-random pairing in American kestrels: mate choice versus intra-sexual competition
Series title Animal Behaviour
DOI 10.1016/S0003-3472(05)80577-9
Volume 44
Issue 5
Year Published 1992
Language English
Publisher Association for the Study of Animal Behaviour
Publisher location London
Description 11 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Animal Behaviour
First page 811
Last page 821
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