SREL Reprint #3291

Habitat structure and colony structure constrain extrapair paternity in a colonial bird

Alejandra G. Ramos1, Schyler O. Nunziata2,3, Stacey L. Lance2, Cristina Rodríguez1,
Brant C. Faircloth4, Patricia Adair Gowaty4,5,6, and Hugh Drummond1

1Departamento de Ecología Evolutiva, Instituto de Ecología,
Universidad Nacional Autónoma de México, Mexico
2Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA
3Department of Biology, University of Kentucky, Lexington, KY, USA
4Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
5Institute of the Environment and Sustainability, University of California, Los Angeles, CA, USA
6Smithsonian Tropical Research Institute, Washington, D.C., USA

Abstract: Individual variation in sexual fidelity and extrapair paternity (EPP) is widely attributed to environmental heterogeneity, but the only variables known to be influential are food abundance and density of conspecific breeders (potential extrapair partners). Habitat structure is thought to impact EPP but is rarely measured and, when considered, is usually confounded with food abundance and predation pressure. To sidestep these confounds, we tested whether EPP is associated with habitat structure variables and with local conspecific density in a species whose nesting habitat is not used for feeding and lacks predators. In a blue-footed booby, Sula nebouxii, colony, the probability of EPP in a female's nest was highest in parts of the study plot where there were few obstacles to locomotion, and was quadratically related to local density of sexually active males, even though local males did not sire the EP chicks. The probability of a male breeder siring EP (extrapair) chicks elsewhere was quadratically related to local density of sexually active males around his nest. From these patterns we infer that both sexes may foray for EP interactions, that males and females nesting at intermediate density are most likely to be accessed by forayers, and that obstacles in the vicinity of a female's nest constrain access of foraying males. To our knowledge, this is the first demonstration that individual variation in EPP is associated with habitat structure in the absence of confounding variation in food availability, predation pressure or breeder quality, and the first evidence that EPP opportunities of female and male breeders are reduced by high density of conspecific breeders above a particular threshold.

Keywords: blue-footed booby, colonial seabird, extrapair paternity, extrapair sire, habitat structure, microsatellite, nest density, spatial location, Sula nebouxii

SREL Reprint #3291

Ramos, A. G., S. O. Nunziata, S. L. Lance, C. Rodríguez, B. C. Faircloth, P. A. Gowaty, and H. Drummond. 2014. Habitat structure and colony structure constrain extrapair paternity in a colonial bird. Animal Behaviour 95(2014): 121-127.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).