Assessing the effects of natural disturbance on a neotropical migrant songbird

Large‐scale natural habitat disturbances can play major roles in structuring the distribution of individuals and ecosystems, and can exert substantial selective pressures. The magnitude of these effects depends on the spatial and temporal scale of the disturbance, as well its frequency, intensity, and predictability. In January 1998, the worst ice storm in documented Canadian history struck southern Ontario and Quebec. This storm affected >10⁶ ha of forest, causing widespread damage. One region negatively affected by the storm is home to a large breeding population of Cerulean Warblers, Dendroica cerulea. This population has been studied since 1994, thereby allowing a unique opportunity to examine the effects of a large‐scale natural habitat disturbance on the reproductive ecology and behavior of this Neotropical migrant songbird. We addressed two main questions: (1) did Cerulean Warbler reproductive success change after this habitat disturbance, and (2) did the breeding population exhibit a shift in habitat selection patterns in response to this habitat disturbance? The January 1998 ice storm caused a significant reduction in the amount of forest canopy foliage in our study area the following spring. This was followed by a significant decline in Cerulean Warbler reproductive output in the 1998 breeding season. In 1999, Cerulean Warblers demonstrated a significant increase in territory size and a significant shift in nest‐site location patterns; these shifts were accompanied by a significant increase in reproductive success. The 1999 shifts in territory and nest‐site location patterns were effected by the same individuals who were failed breeders in 1998. This suggests that Cerulean Warblers possess a degree of plasticity in their habitat affinities, and that this plasticity rendered the population somewhat resilient to this particular disturbance.