title: Recruitment to a seabird population depends on environmental factors and on population size.
abstract: 1. A novel capture-mark-recapture (CMR) method was used to build a multistate model of recruitment by young birds to a breeding population of common guillemots Uria aalge on the Isle of May, Scotland. Recruitment of a total of 2757 individually marked guillemots over 17 years was modelled as a process where individuals had to move from an unobservable state at sea, through a nonbreeding state present in the colony, to the breeding state. The probabilities of individuals returning to the colony in a given year, at age 2 and 3-4 years, were positively correlated with an environmental covariate, the winter North Atlantic Oscillation index (WNAO) in the previous years. 2. For 2 year olds, there was a negative relationship with breeding population size, suggesting that density dependence operated in this colony through limitation of food or some other resource. 3. Survival over the first 2 years of life varied with cohort, but was unrelated to the WNAO. Mean survival over this 2-year period was high at 0.576 (95% CI: 0.444; 0.708). 4. This high survival, combined with a low 'local' survival after age 5 years of 0.695 (0-654; 0.733) and observations of Isle of May chicks at other colonies, suggests that most surviving chicks return to the natal colony before deciding whether to recruit there or move elsewhere.
authors.affiliation: Centre for Ecology and Hydrology, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, UK Laurent.crespin@mpl.ird.fr
authors.forename: Laurent
authors.initials: L
authors.lastname: Crespin
authors.forename: Michael P
authors.initials: MP
authors.lastname: Harris
authors.forename: Jean-Dominique
authors.initials: JD
authors.lastname: Lebreton
authors.forename: Morten
authors.initials: M
authors.lastname: Frederiksen
authors.forename: Sarah
authors.initials: S
authors.lastname: Wanless
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D046091:Charadriiformes / Q000254:growth & development* / Q000502:physiology*; D004777:Environment; D005260:Female; D008136:Longevity / Q000502:physiology; D008297:Male; D008954:Models, Biological; D011156:Population Density; D011157:Population Dynamics; D011158:Population Growth; D013223:Statistics as Topic