Behavioral Ecology Advance Access published online on October 23, 2008
Behavioral Ecology, doi:10.1093/beheco/arn136
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Experimental evaluation of sex differences in territory acquisition in a cooperatively breeding bird
a Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands b Department of Biology, 2125 Derring Hall, Virginia Tech, Blacksburg, VA 24061, USA c Centre for Ecology, Evolution and Conservation, Department of Biological Sciences University of East Anglia, Norwich, NR4 7TJ, United Kingdom d Nature Seychelles, PO Box 1310, Mahe, Republic of Seychelles
Address correspondence to C. Eikenaar. E-mail: eikenaar{at}vt.edu.
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Abstract |
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In many species, territory ownership is a prerequisite for reproduction; consequently, factors that affect success in territory acquisition can have a large impact on fitness. When competing for territories, some individuals may have an advantage if, for example, they are phenotypically superior or more familiar with the site than others. The relative importance of the many factors involved in territory acquisition is, at present, unclear. We studied patterns of natural territory acquisition in a closed and saturated population of Seychelles warblers. Furthermore, by removing breeders, we experimentally investigated the relative importance, to territory acquisition, of a range of factors and assessed whether this differed between the sexes. In both sexes, the main route to natural territory acquisition was to disperse from the natal territory to immediately claim a vacant dominant position. Males were older than females when acquiring a territory for the first time. In the removal experiment, for both sexes, the proximity of an individual's natal territory to a vacant dominant position was positively related to the individual's chance of claiming the vacancy. Older males were more likely to gain an experimental vacant dominant position than were young males, whereas age did not affect territory acquisition in females. In the Seychelles warbler, the degree of intrasexual competition for territory ownership may be stronger for males than for females because territory ownership is a prerequisite for male reproduction, whereas females can reproduce on their natal territory. In such competition, young males subsequently lose out to older ones.
Key words: Acrocephalus sechellensis, age-related dominance, cooperative breeding, female choice, intrasexual competition, natal dispersal.
Received 4 July 2008; revised 16 September 2008; accepted 23 September 2008.