Parental care and sexual selection in socially monogamous crested auklets (Aethia cristatella)

Fraser, Gail S. (1999) Parental care and sexual selection in socially monogamous crested auklets (Aethia cristatella). Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

In this thesis I investigate the relationships between chick growth, parental attendance and sexual selection in a seabird that exhibits mutual mate choice. I quantified breeding parameters, sexual roles in parental care and how ornamentation relates to parental care in Crested Auklets (Aethia cristatella) at Buidir Island, Alaska. Growth rates averaged about 9.98 g/day during the linear phase and chicks fledged at an average mass of 247 g and a wing length of 124 mm at 34.5 days after hatching. Crested Auklet chicks, like those of other diurnally active auklet species, grow relatively fast and depart at a younger age compared to the chicks of two nocturnal auklet species. Parental care patterns were studied using radio telemetry. In 1996, I found no sexual differences in parental care behaviours and low attendance rates, suggesting a poor food year. In 1997 and 1998, I found significant differences in parental care between males and females: males attended and brooded their single chick 45% more than females, while females provisioned 47% more than males. Males have a larger and strongly hooked bill and are more aggressive than females and I hypothesized that males are better equipped than females to guard young chicks. While this bill shape difference probably evolved through intra-sexual selection, it has ecological consequences because male auklets delivered larger prey items than females. Males brought in 30% more larger euphausiids whereas females brought in 36% more smaller copepods. I examined the relationship between crest length and parental effort using simple game theory models. I evaluated whether crest length indicated an ability to provide parental care (a direct benefit) or whether crest length advertised a indirect benefit such as good genes. Male attendance and provisioning rates were not related to crest length, however early chick provisioning by males was positively correlated with their partner's crest length. Female provisioning rates were negatively correlated with own crest length, while early attendance was positively correlated with their partner's crest length. Because both male and female parental effort was positively correlated with their partner's crest length, suggests that crest length was an advertisement of an indirect benefit.

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