Mismatch between diurnal home ranges and roosting areas in the Wood Thrush (Hylocichla mustelina): Possible role of habitat and breeding stage

摘要

The behavior of roosting birds has received little attention from ornithologists, despite its importance for understanding the complete avian circadian cycle. We examined the spatial arrangement of roosts in relation to diurnal home ranges for the declining Wood Thrush (Hylocichla mustelina) on its breeding grounds in coastal Virginia, USA. To our knowledge, this is the first broad description of roosting ecology for a North American migratory passerine during the breeding season. The primary objective of this study was to determine whether roost sites and diurnal use areas overlapped. Secondly, using LiDAR, we tested the hypothesis that birds roosted at sites with higher local vegetation density than random points. Lastly, we explored the effect of nest status on the roosting patterns of pairs. We tracked 37 radio-tagged males to construct 95% kernel diurnal home ranges. In 10 home ranges we also tagged the female mates. Both sexes were tracked at night to roosting locations. Of 74 male roosts, 31% were located outside diurnal home ranges. LiDAR-derived vegetation density was similar to 7% higher at roost sites than at random points within diurnal home ranges, and young birds roosted farther from peak diurnal use areas than older birds, suggesting a role of roosting habitat quality. Nest status had a significant effect on pair roosting patterns, as females with active nests roosted exclusively in nest cups, whereas males roosted an average of 121.8 m (95% CI = 72.6-204.2, n = 11) away on equivalent nights. Once nests fledged or failed, males roosted within diurnal home ranges while appearing to guard females. We propose that the observed mismatch in male diurnal home ranges and nocturnal roost sites may be based on optimal roosting conditions at those sites; however, male solicitation of extrapair copulations from fertile neighboring females during the morning and evening insemination windows should also be considered.