Compensation for lateral drift due to crosswind in migrating European bee-eaters

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Sapir, N., Horvitz, N., Wikelski, M., Avissar, R. and Nathan, R. 2014. Compensation for lateral drift due to crosswind in migrating European bee-eaters. Journal of Ornithology 155:745-753.

 

ABSTRACT

Billions of seasonally migrating birds and insects use two principal modes of flight, i.e., flapping and soaring–gliding. Flight mode is known to have strong effects on energy expenditure and speed of migration, yet its influence on the migratory track has rarely been investigated. Using radio telemetry, we studied the effects of crosswind on European Bee-eaters (Merops apiaster) during their spring migration with respect to different flight modes. Flapping, soaring–gliding, and mixed flight in which the birds flapped during gliding were distinguished by radio signals while the birds were flying en route over southern Israel. The regional atmospheric modeling system was applied in high spatial (1 km × 1 km) and temporal (5 min) resolution to estimate winds encountered aloft. We analyzed data from 11 birds that flew over a total distance of 810 km and found that lateral drift due to side wind did not differ among birds engaged in different flight modes. Overall, there was almost no effect of crosswind speed on bird lateral speed, as the regression slope was 0.31 (indicting mild lateral drift) and the regression’s R 2 was 0.01. Therefore, we conclude that migrating bee-eaters compensated for crosswind during their spring migration and that this response was not dependent on bird flight mode.