Prior residence effect in wintering male Eurasian siskins is not related to resource holding power

摘要

Animals competing for resources follow a general rule for which prior residents usually win contests over intruders. This prior residence effect might arise because animals possess a genetically fixed convention so that ‘residents always win’ (i.e. an uncorrelated asymmetry), because residents have a higher resource holding power (RHP) than intruders or because residents have a higher motivation to defend territories (i.e. pay-off asymmetry). The discrimination between these different hypotheses, though, has proven to be difficult. Eurasian siskins (Spinus spinus) provide us with an adequate opportunity to test for the effect of RHP on the prior residence effect. Siskins show two different strategies while in the wintering grounds: residents remain for several weeks on a given location while transients continuously move and residents are dominant over transients. The black bib area of male siskins signals their RHP. In this study, we compared the black bib area of a large sample of male resident and transient siskins and we found no differences between the two subpopulations. Hence, residence status in this species is not related to black bib size, which is a good proxy for RHP. Our results support the view that asymmetries in RHP are not required to explain the prior residence effect. We discuss the important implications that it has on the evolution of partial migration.