Wing morphology covaries with migration distance in a highly aerial insectivorous songbird

According to classical prediction of aerodynamic theory,birds and other powered fliers that migrate over long distances should have longer and more pointed wings than those that migrate less.However,the association between wing morphology and migratory behavior can be masked by contrasting selective pressures related to foraging behavior,habitat selection and predator avoidance,possibly at the cost of lower flight energetic efficiency.We studied the handwing morphology of Eurasian barn swallows Hirundo rustica from four populations representing a migration distance gradient.This species is an aerial insectivore,so it flies extensively while foraging,and may migrate during the day using a‘fly-and-forage’migration strategy.Prolonged foraging flights may reinforce the effects of migration distance on flight morphology.We found that two wings’aerodynamic properties—isometric handwing length and pointedness,both favoring energetically efficient flight,were more pronounced in barn swallows from populations undertaking longer seasonal migrations compared to less migratory populations.Our result contrast with two recent interspecific comparative studies that either reported no relationship or reported a negative relationship between pointedness and the degree of migratory behavior in hirundines.Our results may thus contribute to confirming the universality of the rule that longer migrations are associated with more pointed wings.

Extra food provisioning does not affect behavioral lateralization in nestling lesser kestrels

Costs and benefits of brain lateralization may depend on environmental conditions.Growing evidence indicates that the development of brain functional asymmetries is adaptively shaped by the environmental conditions experienced during early life.Food availability early in life could act as a proxy of the environmental conditions encountered during adulthood,but its potential modulatory effect on lateralization has received little attention.We increased food supply from egg laying to early nestling rearing in a wild population of lesser kestrels Falco naumanni,a sexually dimorphic raptor,and quantified the lateralization of preening behavior(head turning direction).As more lateralized individuals may perform better in highly competitive contexts,we expected that extra food provisioning,by reducing the level of intra-brood competition for food,would reduce the strength of lateralization.We found that extra food provisioning improved nestling growth,but it did not significantly affect the strength or direction of nestling lateralization.In addition,maternal body condition did not explain variation in nestling lateralization.Independently of extra food provisioning,the direction of lateralization differed between the sexes,with female nestlings turning more often toward their right.Our findings indicate that early food availability does not modulate behavioral lateralization in a motor task,suggesting limited phenotypic plasticity in this trait.