SEX DIFFERENCES IN NEST VISITATION BY CHICK-REARING MARBLED MURRELETS

• Published in: The Condor (Los Angeles, Calif.) Calif.), 2002-02, Vol.104 (1), p.178-183
• Main Authors: Bradley, Russell W, Tranquilla, Laura A. McFarlane, Vanderkist, Brett A, Cooke, Fred
• Format: Article
• Language: English
• Subjects: Aerial locomotion; Animal behavior; Animal ethology; Aves; Aviculture; Biological and medical sciences; Bird nesting; Birds; Brachyramphus marmoratus; Breeding; British Columbia; Chicks; Female animals; Females; Fundamental and applied biological sciences. Psychology; Male animals; male bias; Males; Marbled Murrelet; Nesting sites; Ornithology; provisioning; Psychology. Psychoanalysis. Psychiatry; radio-telemetry; Sea birds; sex ratio; SHORT COMMUNICATIONS; Vertebrata
• ISSN: 0010-5422; 1938-5129; 2732-4621
• DOI: 10.1650/0010-5422(2002)104[0178:SDINVB]2.0.CO;2

We report a significant male bias in dawn and dusk nest visitations of breeding, radio-marked Marbled Murrelets (Brachyramphus marmoratus) during the chick rearing period in Desolation Sound, British Columbia, Canada, from 1998–2000. Overall visitation rates of males during chick rearing were 1.3 times greater than those of females. Dusk visitation rates by males with active nests were 1.8 times greater than those of females. Male visitation rates were similar between early and late chick rearing, both within and among individuals. However, female visitation rates during late chick rearing were significantly lower than female rates early in rearing, both within and between individuals. In addition, between-sex comparisons of nest visitation during early and late chick rearing showed significant reductions in female effort relative to males, only during late chick rearing. These results suggest that male birds may provision chicks more often than females, especially during the last half of chick rearing. These findings offer a behavioral explanation for the annual male bias of birds flying inland during the chick rearing period at Theodosia Inlet in Desolation Sound from 1994–1999. Although female-biased provisioning has been documented in several species, male-biased provisioning has not been widely reported in other alcids. Diferencias de Sexo en la las Visitas al Nido en Brachyramphus marmoratus durante la Crianza de Pichones Resumen. Presentamos evidencia sobre un sesgo hacia los machos en las visitas a nidos efectuadas al amanecer y el crepúsculo durante la crianza de pichones, en individuos marcados con radios en Desolation Sound, Columbia Británica, Canadá, entre 1998–2000. La tasa de visitas de los machos fue 1.3 veces mayor que la de las hembras. La tasa de visitas de los machos al crepúsculo con nidos activos fue 1.8 veces mayor que las hembras. La tasa de visitas de los machos fue constante a través del período de crianza, tanto para un mismo individuo como entre individuos. Sin embargo, la tasa de visitas de las hembras fue significativamente menor al final que al inicio de la crianza, tanto para un mismo individuo como entre individuos. Además, la tasa de visitas de las hembras fue menor que la de los machos al final de la crianza. Estos resultados sugieren que los machos abastecen a los pichones en mayor medida que las hembras, especialmente en la última parte de la crianza. Asimismo, los resultados ofrecen una explicación conductual para la d