Meeting Abstract
Locomotor development among species is remarkably diverse, and we sought to improve understanding of the selective pressures driving this diversification. Herein we demonstrate relationships between the onset of flight capacity at the end of the post-natal stage of development and the daily predation rate during this phase of ontogeny. Focusing on passerines, we studied 11 species in a temperate forest in Arizona, USA (average predation rate 0.028/day), and 15 species in a tropical forest in Malaysia (average predation rate 0.050/day). We measured flight capacity using video recordings (120 Hz) from drop tests, which we digitized and analyzed for rate of whole-body acceleration. In both study areas, species experiencing higher predation rates developed more rapidly and spent less time in the nestling phase. In the temperate forest, flight capacity at fledging was negatively related to predation rate. For example, gray-headed juncos, an open-cup nesting species, fledge 11 days post hatching (d.p.h) but can only support 24% of their body weight using their wings, while mountain chickadees (cavity nesters) fledge at 20 d.p.h. and are fully capable of flight. In tropical forest, higher predation rates were associated with more rapid development of flight capacity, but most of the species (73%) could fly or support at least 81% of their body weight (w) at fledging, and all could support > 50% w. In sum, flight capacity was negatively related to predation rate in temperate forest and positively related in tropical forest. Comparing non-cavity nesting species, flight ability to improve avoidance of predation after fledglings leave the nest seems to be of greater priority in tropical forests. Overall, our results provide novel insight into the role of predation in promoting diversity of locomotor performance during ontogeny.
