MULTISCALE ANALYSIS OF THE EFFECTS OF RAINFALL EXTREMES ON REPRODUCTION BY AN OBLIGATE RIPARIAN BIRD IN URBAN AND RURAL LANDSCAPES

摘要

Headwater forests serve many ecological functions and may be particularly responsive to changes in climate and land use. Riparian birds can serve as indicators of changes in their associated ecosystems. Little known, however, are combined influences of climate and land use on riparian birds and riparian ecosystems. We examined multiscale associations between these environmental conditions and reproduction of the Louisiana Waterthrush (Seiurus motacilla), a riparian-obligate songbird that breeds in the eastern United States. Specifically, we measured variables at multiple spatial and temporal scales to model crucial components of individual fecundity, using an information-theoretic approach. We monitored 190 nests in 139 territories within 13 drainages from 2002 to 2005. Daily nest survival reached a maximum when mean rainfall was intermediate (3-10 mm day~-1) during the nesting period. Nestling survival, by contrast, reached its maximum with high amounts of rainfall (>14 mm day~-1). Nestling survival declined with increasing territory size and was lowest in areas that were far from clearcuts and fields (≥160 m) but were surrounded by large expanses of fields (≥40% within 1.75 km). Urban land uses surrounding drainages, proximity to edges, measures of food availability, differences among years, and timing of nesting had weak, if any, effects on Louisiana Waterthrush reproduction. These findings indicate that reproduction by this riparian obligate is negatively associated with (1) rainfall extremes and agricultural land use and (2) size of the territory defended by the male. Received 2 January 2008, accepted 17 June 2008.