Meeting Abstract

P1.5  Sunday, Jan. 4  Breeding and molt in Neotropical bird communities ECHEVERRY-GALVIS, M.A.; Princeton University mechever@princeton.edu

The temporal regulation of key events, such as molt and reproduction in the life cycle of individual birds requires highly sensitive internal mechanisms that can respond to variations in environmental conditions. For most tropical high-altitude species little information is available regarding the annual regulation of molt and reproduction. I surveyed breeding and molting periods of various bird species found at 2700-2900 meters altitude in four patches of cloud mountain forest of different sizes in Colombia. I used laparotomies to determine breeding condition, and scored molt in flight and contour feathers in 775 individuals. Weather conditions and resource availability were monitored. Breeding occurred on a seasonal basis with individuals fully regressing their gonads at different times of year. In the two big areas (larger than 800ha) breeding seemed to be bimodal with a hiatus of about 4 months, while in the small areas (smaller than 15ha) breeding was unimodal. Breeding periods were correlated with increased resource abundance (insects and flowers) as well as photoperiodic in different areas. Molt was not restricted to the post-breeding period in any area, overlapping with enlarged gonads. Like breeding, molt occurred earlier in males than in females. Molting periods were correlated with ambient temperature, photoperiod and insect abundance. Molt/breeding overlap was more common in the small compared to the big areas, and was present in 46% of all species. These data raise questions about the ecological factors and the physiological mechanisms that allow these two events to occur simultaneously in certain species. Current studies are investigating the hormonal profiles of individuals that show molt/breeding overlap to understand the proximate factors that are at the basis of this phenomenon among Neotropical cloud mountain birds.