title: Corticosterone shifts reproductive behaviour towards self-maintenance in the barn owl and is linked to melanin-based coloration in females.
abstract: Trade-offs between the benefits of current reproduction and the costs to future reproduction and survival are widely recognized. However, such trade-offs might only be detected when resources become limited to the point where investment in one activity jeopardizes investment in others. The resolution of the trade-off between reproduction and self-maintenance is mediated by hormones such as glucocorticoids which direct behaviour and physiology towards self-maintenance under stressful situations. We investigated this trade-off in male and female barn owls in relation to the degree of heritable melanin-based coloration, a trait that reflects the ability to cope with various sources of stress in nestlings. We increased circulating corticosterone in breeding adults by implanting a corticosterone-releasing-pellet, using birds implanted with a placebo-pellet as controls. In males, elevated corticosterone reduced the activity (i.e. reduced home-range size and distance covered within the home-range) independently of coloration, while we could not detect any effect on hunting efficiency. The effect of experimentally elevated corticosterone on female behaviour was correlated with their melanin-based coloration. Corticosterone (cort-) induced an increase in brooding behaviour in small-spotted females, while this hormone had no detectable effect in large-spotted females. Cort-females with small eumelanic spots showed the normal body-mass loss during the early nestling period, while large spotted cort-females did not lose body mass. This indicates that corticosterone induced a shift towards self-maintenance in males independently on their plumage, whereas in females this shift was observed only in large-spotted females.
authors.affiliation: Swiss Ornithological Institute, Sempach, Switzerland. bettina.almasi@vogelwarte.ch
authors.forename: Bettina
authors.initials: B
authors.lastname: Almasi
authors.forename: Alexandre
authors.initials: A
authors.lastname: Roulin
authors.forename: Lukas
authors.initials: L
authors.lastname: Jenni
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003116:Color; D003345:Corticosterone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D004343:Drug Implants; D005247:Feeding Behavior; D005260:Female; D006128:Growth / Q000187:drug effects; D006702:Homing Behavior; D008297:Male; D008543:Melanins / Q000502:physiology*; D009425:Nesting Behavior / Q000187:drug effects; D016487:Parenting; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D020305:Strigiformes / Q000502:physiology*; D013534:Survival
chemical_list: D004343:Drug Implants; D008543:Melanins; D003345:Corticosterone