Largescale nahiral habitat disturbances can play major roles in structuring
the distribution of individuak and ecos ystems and can exert substantial selective pressures- The magnitude of these effects depends on the spatial and temporal scale of the disturbance, as well its kequency, intensity and predictability. In January 1998, the worst ice stom in documented Canadian history struck southern Ontario and Quebec. This storm affected over 10 million hectares of forest causing widespread damage. One of the regions negatively af5ected by the stonn is home to a large b;.~ 1-s population of Cerulean Warblers, Dendroica cerulea. This population has been studied since 1 994 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 Warb ler reproductive - success change afier this habitat disturbance?, and (2) Did the breeding population exhibit a shifl in habitat selection patterns in response to this habitat disturbance? The January 1998 ice storm resulted in a significant reduction in the amount of foliage in the forest canopy of our study area in the following spring. This was followed by a sigaificant decline in Cerulean Warbler reproductive output in the 1998 breeding season. In 1999, Cerulean Warblers demonstrated a significant increase in temtory 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 affected 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.

: Cerulean Warbler; Dendroica cenrlea; forest canopy; ice storm; natural habitat disturbance; Neotropical migrant; nest-site characteristics; Ontario; population resilience; territory size