Laterality and flight: Concurrent tests of side-bias and optimality in flying tree swallows

Abstract

Behavioural side-bias occurs in many vertebrates, including birds as a results of hemispheric specialization and can be advantageous by improving response times to sudden stimuli and efficiency in multi-tasking. However, behavioural side-bias can lead to morphological asymmetries resulting in reduced performance for specific activities. For flying animals, wing asymmetry is particularly costly and it is unclear if behavioural side-bias will expressed in flight; the benefits of quick response time afforded by side-biases must be balanced against the cost of less efficient flight due to the morphological asymmetry side-bias may incur. Thus, competing constraints could lead to context-dependent expression or suppression of side-bias in flight. In repeated flight trials through an outdoor tunnel with obstacles, tree swallows (Tachycineta bicolor) preferred larger openings, but we did not detect either individual or population-level side-biases. Thus, while observed behavioural side-blases during substrate-foraging and copulation are common in birds, we did not see such side-bias expressed in obstacle avoidance in flight. This finding highlights the importance of behavioural context for investigations of side-bias and hemispheric laterality and suggests both proximate and ultimate trade-offs between species-specific cognitive ecology and flight biomechanics. © 2008 Mandel et al.