CONSTRAINTS ON DOUBLE BROODING IN A NEOTROPICAL MIGRANT, THE HOODED WARBLER

We examined the constraints on double brooding in Hooded Warblers (Wil sonia citrina) to explain why 56% of females with successful first nes ts did not attempt second broods. Double brooded females fledged on av erage 1.9 more young than single brooded females. Double brooded femal es nested significantly earlier than single brooded females, but many females with early nests did not double brood. There were no significa nt differences among single and double brooded females in age, experie nce, body condition, or reproductive output at their first nest. Femal e breeding strategy did not depend on male age or male feeding effort at the first nest. Double brooded individuals were usually feeding fle dglings while undergoing their pre-basic molt, and the main cost of be ing double brooded was a three week delay in molt compared with single brooded birds. This delay in molt could impose a high energetic cost due to the overlap of molt and fledgling care, and a time cost in term s of delaying migration and the acquisition of a winter territory.