Movements of Fledgling Ovenbirds (Seiurus aurocapilla) and Worm-Eating Warblers (Helmitheros vermivorum) within and Beyond the Natal Home Range

[摘要] Although postfledging movement patterns have been described for several species, the factors that influence these movements remain unclear. We quantified natal home-range size and dispersal patterns of two songbird species and evaluated the relative importance of nestling condition, brood size, predation risk, and habitat structure on postfledging movements. We radiotagged and tracked 51 Ovenbirds (Seiurus aurocapilla) and 60 Worm-eating Warblers (Helmitheros vermivorum) between 2004 and 2007. For each radiotagged bird, we calculated distances from daily locations to the original nest, successive distances between daily locations, mean dispersal distance from the natal area, number of days before dispersal, and natal home-range size. We built and ranked alternative models to represent mechanisms that potentially influence movements 2 days after fledging. The natal home-range size of Worm-eating Warblers (10.4 ha ± 1.50 [SE]) was twice that of Ovenbirds (5.0 ha ± 0.56). Fledgling age was positively correlated with the distance moved from the nest and between daily locations. Relative body mass at the time of fledging was positively associated with the mean distance between daily locations 2 days after fledging. This research generated two important insights into postfledging ecology: (1) that conditions experienced by birds in the nest may ultimately facilitate or constrain their ability to locate suitable habitat, which is known to influence fledgling survival; and (2) that large natal home ranges and relatively long dispersal distances away from the natal area may contribute to area sensitivity in songbirds.

[学科分类] 动物科学

[关键词] dispersal;Helmitheros vermivorum;movements;natal home range;Ovenbird;postfledging;Seiurus aurocapilla;Worm-eating Warbler