Immigrants are attracted by local pre‐breeders and recruits in a seabird colony

• Published in: The Journal of animal ecology 2014-09, Vol.83 (5), p.1015-1024
• Main Authors: Szostek, K. Lesley, Schaub, Michael, Becker, Peter H, Weimerskirch, Henri
• Format: Article
• Language: English
• Subjects: adults; Animal and plant ecology; Animal ecology; Animal Migration; Animal, plant and microbial ecology; Animals; Aves; Bayes Theorem; Bayesian modelling; Biogeography; Biological and medical sciences; Birds; Breeding; Breeding sites; Charadriiformes - physiology; common tern; conspecific attraction; Demography; dispersal; Fundamental and applied biological sciences. Psychology; General aspects; General aspects. Techniques; Germany; Immigration; life history; local recruitment; mate availability; Methods and techniques (sampling, tagging, trapping, modelling...); Models, Statistical; Nonnative species; Population Dynamics; Population ecology; Population estimates; Population recruitment; Productivity; public information; recruitment; Reproductive success; Sea birds; seabirds; Sterna hirundo; Time Factors; transponders; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Wildlife management
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/1365-2656.12206

Immigration is a major demographic factor shaping population dynamics. However, due to methodological difficulties, the extent of immigration and factors affecting immigration are insufficiently studied. This is also true for seabird colonies. We estimated annual immigration based on a long‐term study of a colony of common terns Sterna hirundo marked with transponders, using a Bayesian integrated population model that links colony size and productivity with individual life histories. Strong annual fluctuations in the number of immigrants were found. To identify whether colony‐specific covariates influenced immigration, we related the number of immigrants to various proxy variables for breeding site quality, specifically colony size, productivity, number of local subadults and local recruits. Numbers of local recruits and local subadults showed strong positive correlations with number of immigrants. We found that variation in immigration rate had strongly contributed to variation in colony growth rate, more so than variation in local recruitment or adult survival. Collectively, results suggest that immigration strongly affects colony growth rate, that the driving force behind immigration is natal dispersal and that immigrants were attracted by local recruits.