Predictors of floater status in a long-lived bird: a cross-sectional and longitudinal test of hypotheses
Article first published online: 17 OCT 2008
© 2008 The Authors. Journal compilation © 2008 British Ecological Society
Journal of Animal Ecology
Volume 78, Issue 1, pages 109–118, January 2009
How to Cite
Sergio, F., Blas, J. and Hiraldo, F. (2009), Predictors of floater status in a long-lived bird: a cross-sectional and longitudinal test of hypotheses. Journal of Animal Ecology, 78: 109–118. doi: 10.1111/j.1365-2656.2008.01484.x
- Issue published online: 11 DEC 2008
- Article first published online: 17 OCT 2008
- Received 17 April 2008; accepted 1 September 2008; Handling Editor: Jonathan Wright
- territory acquisition
- 1Few studies have been capable of monitoring the nonterritorial sector of a population because of the typically secretive behaviour of floating individuals, despite the existing consensus over the demographic importance of floating. Furthermore, there is almost no information on floating behaviour for migratory species.
- 2The factors that determine whether an individual will be a floater or a territory owner have been framed into five, non-mutually exclusive hypotheses: (i) territory holders are morphologically superior to floaters (resource-holding potential hypothesis); (ii) age confers skills and fighting motivation which lead to social dominance and territory ownership (age hypothesis); (iii) occupancy time of a site determines asymmetries in its knowledge, familiarity and value for potential contenders (site-dominance hypothesis); (iv) contenders use an arbitrary rule to settle contests leading to pre-defined cut-off points for a biologically meaningful trait (e.g. age, body size) separating floaters from territory holders (arbitrary convention hypothesis); and (v) floaters set up a ‘war of attrition’ at arbitrarily chosen territories (arbitrary attrition hypothesis).
- 3We tested these hypotheses using long-term data on a long-lived, migratory raptor, the black kite Milvus migrans Boddaert.
- 4Floating status was best explained by the concerted action of mechanisms consistent with the age and site-dominance hypotheses.
- 5In both cross-sectional and longitudinal analyses, acquisition of a territory was determined by a complex interaction between age and early arrival from migration, suggesting: (i) a progressive incorporation of early arriving individuals in the territorial contingent of the population, and (ii) the existence of an alternative restraint strategy of delayed territoriality mediated by long-term acquisition of social dominance.
- 6Such results suggested that territory acquisition was mediated by the establishment of site dominance through pre-emption and, secondarily, despotism. In this population, age and arrival date aligned individuals along a demographic continuum ranging from successful breeders monopolizing high-quality resources to floaters with no resources, consistent with the notion of floating as an extreme form of breeding failure.