Effect of yolk corticosterone on begging in the yellow-legged gull

Behavioral lateralization is widespread across vertebrates. The development of lateralization is affected by both genetic and environmental factors. In birds, maternal substances in the egg can affect offspring lateralization via activational and/or organizational effects. Corticosterone affects the development of brain asymmetry, suggesting that variation in yolk corticosterone concentration may also influence post-natal behavioral lateralization, a hypothesis that has never been tested so far. In the yellow-legged gull (Larus michahellis), we increased yolk corticosterone concentration within physiological limits and analyzed the direction of lateralization of hatchlings in reverting from supine to prone position ('RTP' response) and in pecking at dummy parental bills to solicit food provisioning ('begging' response). We found that corticosterone treatment negatively affected the frequency of begging and it may cause a slight leftward lateralization. However, the direction of lateralization of the RTP response was not affected by corticosterone administration. Thus, our study shows a maternal effect mediated by corticosterone on a behavioral trait involved in parent-offspring communication during food provisioning events. The findings on lateralization are not conclusive due to the weak effect size but provide information for further ecological and evolutionary studies, investigating mechanisms underlying the development of lateralization

Behavioural stress response and melanin-based plumage colouration in barn swallow nestlings

Consistent and correlated inter-individual differences in behaviours, the so-called 'personalities', have been identified in many vertebrates. The ability to respond to stressful events is part of personalities and can have important fitness consequences, as it determines how individuals cope with environmental challenges. As a consequence of pleiotropic effects of genes involved in several functions, inter-individual differences in behavioural responses can be associated with phenotypic traits, like melanin-based plumage colouration in birds. We examined the association between three proxies of the behavioural stress response and breast plumage colouration in barn swallow (Hirundo rustica) nestlings. We found that nestling behavioural responses were consistent within individuals and similar among siblings, thus suggesting that these behaviours may contribute to define individual 'personalities'. However, nestling behavioural stress response was not significantly predicted by variation in breast plumage colouration, indicating that in juveniles of this species melanin-based colouration does not convey to conspecifics reliable information on individual ability to cope with stressful events

Behavioural stress response and melanin-based plumage colouration in barn swallow nestlings

Consistent and correlated inter-individual differences in behaviours, the so-called 'personalities', have been identified in many vertebrates. The ability to respond to stressful events is part of personalities and can have important fitness consequences, as it determines how individuals cope with environmental challenges. As a consequence of pleiotropic effects of genes involved in several functions, inter-individual differences in behavioural responses can be associated with phenotypic traits, like melanin-based plumage colouration in birds. We examined the association between three proxies of the behavioural stress response and breast plumage colouration in barn swallow (Hirundo rustica) nestlings. We found that nestling behavioural responses were consistent within individuals and similar among siblings, thus suggesting that these behaviours may contribute to define individual 'personalities'. However, nestling behavioural stress response was not significantly predicted by variation in breast plumage colouration, indicating that in juveniles of this species melanin-based colouration does not convey to conspecifics reliable information on individual ability to cope with stressful events