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Postfledging Occupancy of Breeding Sites by Female Common Murres (Uria aalge)

Michael P. Harris and Sarah Wanless
The Auk
Vol. 120, No. 1 (Jan., 2003), pp. 75-81
DOI: 10.2307/4090142
Stable URL: http://www.jstor.org/stable/4090142
Page Count: 7
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Postfledging Occupancy of Breeding Sites by Female Common Murres (Uria aalge)
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Abstract

Virtually all female Common Murres (Uria aalge) continued to visit the colony after their mate had taken the chick to sea. There were significant differences among years, but the average time between a chick fledging and a female last being seen at the colony was 13 days (range 0-36). In over 99% of instances, the female was at her breeding site. On ∼5% of days she was joined by another male, and in a few cases (8% of those days) copulation was observed. None of those transient matings persisted into the next season, even when the original male did not return; thus, we found no support for the hypothesis that females might be looking for replacement mates in case they were widowed. The most successful females (in terms of breeding output over several years) tended to have the longest periods of postfledging visiting, apparently because such birds fledged their chicks early in the season, but there was no difference in daily frequency of attendance. We conclude that successful males and females were maximizing time spent occupying the best breeding sites, even to the extent that only one adult took the chick to sea to complete its development. /// Prácticamente todas las hembras de Uria aalge continuaron visitando la colonia luego de que su pareja había llevado al pichón al mar. Aunque existieron diferencias significativas entre años, el tiempo promedio desde el abandono del nido por el pichón hasta la última vez que se observó la hembra en la colonia fue de 13 días (rango 0-36). En más del 99% de los casos la hembra estuvo en el sitio de su nido. En aproximadamente el 5% de los días estuvo acompañada por otro macho, y en otros pocos casos (8% de esos días) se observaron cópulas. Ninguno de estos apareamientos temporales persistió hasta la temporada siguiente, aún cuando el macho original no regresó. Entonces, no encontramos apoyo para la hipótesis de que las hembras podrían estar buscando parejas de reemplazo en caso de que enviudaran. Las hembras más exitosas (en términos de rendimiento reproductivo a lo largo de varios años) tendieron a presentar los períodos de visita post-emplumamiento más largos, aparentemente porque los polluelos de estas aves emplumaron más temprano en la estación, pero no existió diferencia en la frecuencia diaria de visitas al nido. Concluimos que los machos y hembras exitosos estaban maximizando el tiempo invertido ocupando los mejores sitios de anidación, incluso hasta el punto de que sólo uno de los adultos llevó al pichón al mar para completar sudesarrollo.

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