Bloch, I., Troupin, D., Toledo, S., Nathan, R. and Sapir, N. 2024. Combining radio-telemetry and radar measurements to test optimal foraging in an aerial insectivore bird. eLife. doi: https://doi.org/10.1101/2024.02.18.580922
ABSTRACT
Optimal foraging theory posits that foragers adjust their movements based on prey abundance to 18 optimize food intake. While extensively studied in terrestrial and marine environments, aerial 19 foraging has remained relatively unexplored due to technological limitations. This study, 20 uniquely combining BirdScan-MR1 radar and the ATLAS biotelemetry system, investigates the 21 foraging dynamics of Little Swifts (Apus affinis) in response to insect movements over Israel’s 22 Hula Valley. Insect Movement Traffic Rate (MTR) substantially varied across days, strongly 23 influencing swift movement. On days with high insect MTR, swifts exhibited reduced flight 24 distance, increased colony visit rate, and earlier arrivals at the breeding colony, reflecting a 25 dynamic response to prey availability. However, no significant effects were observed in total 26 flight duration, speed, or daily route length. Notably, as insect abundance increased, inter-27 individual distances decreased. These findings suggest that Little Swifts optimize their foraging 28 behavior in relation to aerial insect abundance, likely influencing reproductive success and 29 population dynamics. The integration of radar technology and biotelemetry systems provides a 30 unique perspective on the interactions between aerial insectivores and their prey, contributing to 31 a comprehensive understanding of optimal foraging strategies in diverse environments.