PREY SIZE INFLUENCES FEMALE COMPETITIVE DOMINANCE IN NESTLING AMERICAN KESTRELS (FALCO-SPARVERIUS)

被引:81
作者
ANDERSON, DJ
BUDDE, C
APANIUS, V
GOMEZ, JEM
BIRD, DM
WEATHERS, WW
机构
[1] MCGILL UNIV, AVIAN SCI & CONSERVAT CTR, Ste Anne De Bellevue H9X 1C0, QUEBEC, CANADA
[2] UNIV CALIF DAVIS, DEPT AVIAN SCI, DAVIS, CA 95616 USA
[3] UNIV PENN, DEPT BIOL, LEIDY LAB, PHILADELPHIA, PA 19104 USA
关键词
AMERICAN KESTREL; AVIAN BROOD REDUCTION; FALCO-SPARVERIUS; SEX RATIO; SEXUAL SIZE DIMORPHISM; SIBLING COMPETITION;
D O I
10.2307/1939299
中图分类号
Q14 [生态学(生物生态学)];
学科分类号
071012 ; 0713 ;
摘要
Body size differences typically influence sibling competition among nestling birds. In many species hatching order determines nestling size rank; however, sexually dimorphic growth may confound this correlation, giving one sex a consistent competitive advantage and leading to differential survival of the sexes. We found that captive female American Kestrel (Falco sparverius) nestlings were larger than male sibling nestmates from shortly after hatching through fledging. When food delivered by parents was small enough to be seized and swallowed immediately by a nestling, females showed clear competitive superiority over male sibling nestmates in scramble competition. Females also took larger portions than males of small, yet unmonopolizeable, items. Competitive ability and gender were unrelated when parents delivered large, unmonopolizeable prey. Choice experiments demonstrated that parent feeding preferences did not account for the females' advantage. Based on the above, we expected fledging sex ratio to become increasingly female biased as nestling mortality increased, because nestling mortality increases and prey size decreases when preferred prey (unmonopolizeable rodents) are not available. Data from a wild kestrel population in eastern Pennsylvania supported this prediction, showing a significant positive relationship between fledging brood size and representation of males in the brood, although we note an alternative explanation for this result. Female competitive dominance and its interaction with prey size may influence the evolution of sexual size dimorphism and primary sex ratio in this species and other raptors.
引用
收藏
页码:367 / 376
页数:10
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