Causes and consequences of distribution patterns in a migratory songbird across its geographic range

The ideal distribution hypothesis states that territorial animals identify habitats with ideal habitat suitability and alter their settlement patterns accordingly. This hypothesis assumes no cost of migrating to a more profitable patch once the current one becomes less profitable. Another underlying assumption is that individuals only use current information while deciding where to breed. To evaluate these assumptions and resultant alternative hypotheses, we studied Ovenbird (Seiurus aurocapilla (L., 1766)) territories during 2000-2001 in six northern hardwood tracts within a landscape composed of wetlands, regenerating stands, small farms and roads. We incorporated data from our own study and from published studies across the Ovenbird geographic range, using an information-theoretic approach. Contrary to the ideal distribution hypothesis, Ovenbird territory density increased with upland openings, but density was similar across clearcut-edge-distance and forest-thinning categories. Relationships between reproduction and territory density were uncertain and therefore provided little evidence against the ideal free distribution hypothesis, but there was some evidence in favor of the alternative costly migration and ideal dominance hypotheses from the analysis of our own data and the meta-analysis, respectively. Finally, territories became denser when fecundity and pairing success were high during the previous year, and this supports the public information hypothesis. We recommend using measures of reproductive success in conjunction with territory density when assessing population status.