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Reproductive success of Yellow-billed Magpies Pica nuttalli in central coastal California

100%

Reynolds M. D., Koenig W. D.

Acta Ornithologica

1997

tom 32

nr 1

99-109

Yellow-billed Magpies in central coastal California had significant variation in laying date of first egg and clutch size within and among years. The length of the breeding season was shorter than for other magpies, but timing of breeding varied widely among years. Early breeders laid larger clutches and, for successful nests, fledged more young than later breeders. Breeding coincided with peak food abundance and breeding early, relative to a particular year's food peak, resulted in higher reproductive success. However, variation in annual reproductive success was not correlated with precipitation or temperature. First-year and mixed-age pairs laid later and smaller clutches than older pairs. First-year females fledged fewer young than older females. Heavier females laid eggs earlier than lighter females. Number of breeding attempts was the most important determinant of reproductive success among years.

Extra-pair copulations in Yellow-billed Magpies Pica nuttalli: preliminary results

84%

Bolen G. M.

Acta Ornithologica

1997

tom 32

nr 1

9-13

The adaptive significance of female extra-pair copulation behavior was investigated in Yellow-billed Magpies, Pica nuttalli, a socially monogamous species. Research was carried out in central coastal California, U.S.A. Observations of female behavior towards extra-pair males during the breeding season suggest that females display a preference for certain extra-pair males. In addition, observations confirm that females can successfully resist male copulation attempts. However, based on a small sample, no significant difference in fledging success was found for nests at which extra-pair visits occurred and those at which they did not. Multilocus DNA fingerprinting analysis is in progress to determine the rate of extra-pair fertilizations. These data will be analyzed for correlations between female behavior towards extra-pair males and those males successfully gaining extra-pair fertilizations, and for differences in fledging success between nests with extra-pair fertilizations and those without extra-pair fertilizations.

Ograniczanie wyników

2 Acta Ornithologica

1 Bolen G. M.

1 Koenig W. D.

1 Reynolds M. D.

2 1997

Wyniki wyszukiwania

Reproductive success of Yellow-billed Magpies Pica nuttalli in central coastal California

Extra-pair copulations in Yellow-billed Magpies Pica nuttalli: preliminary results