Tuesday, 31 October 2017

Insights on dispersal and recruitment paradigms: sex- and age-dependent variations in a nomadic breeder

Oecologia. 2017 Oct 23. doi: 10.1007/s00442-017-3972-7. [Epub ahead of print] Acker P1,2, Francesiaz C3, Béchet A4, Sadoul N5, Lessells CM6, Pijl AS6, Besnard A3. Author information 1 Laboratoire Évolution et Diversité Biologique (EDB) UMR 5174, Université Paul Sabatier, CNRS, ENSFEA, IRD, 118 Route de Narbonne, 31062, Toulouse, France. 2 CEFE UMR 5175, CNRS, PSL Research University, EPHE UM, SupAgro, IRD INRA, 1919 Route de Mende, 34293, Montpellier, France. 3 CEFE UMR 5175, CNRS, PSL Research University, EPHE UM, SupAgro, IRD INRA, 1919 Route de Mende, 34293, Montpellier, France. 4 Centre de Recherche de la Tour du Valat, Le Sambuc, 13200, Arles, France. 5 Les Amis des Marais du Vigueirat, Marais du Vigueirat, Mas Thibert, 13104, Arles, France. 6 Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Postbus 50, 67000 AB, Wageningen, The Netherlands. Abstract Sex- and age-dependence in recruitment and dispersal are often explained by costs arising from competition for holding a breeding territory over the years-a typical feature of species living in stable habitats. For instance, long-lived birds with male territoriality often exhibit large variation in recruitment age and higher dispersal in females and young individuals. As a corollary, we expected that species with ephemeral habitat suitability, and hence nomadic breeding, would show weak age- and sex-dependence in dispersal and low variation in recruitment age, because territory ownership is not maintained over the years. In addition, the higher cost of reproduction in females might not be (over)compensated for by costs of territoriality in males. Accordingly, females would recruit later than males. We explored these variations using multievent capture-recapture models over 13 years, 3479 (2392 sexed) slender-billed gulls (Chroicocephalus genei) and 45 colony sites along the French Mediterranean coast. As expected, variability in recruitment age was low with males recruiting earlier than females. Nonetheless, dispersal in and out of the study area decreased with age and was slightly higher in males than in females. Decreased dispersal with age might result from foraging benefits associated with increased spatial familiarity. Higher dispersal in males might be explained by a male-biased sex ratio or higher philopatry benefits in females (arising from their higher cost of reproduction). Sex- and age-dependent dispersal and recruitment may thus occur in the absence of year-to-year breeding territory ownership, which stresses the importance of considering other processes in shaping recruitment and dispersal patterns. KEYWORDS: Capture–recapture; Colonial species; Multievent models; Temporary emigration; Unstable habitats PMID: 29063200 DOI: 10.1007/s00442-017-3972-7