title: Physiological and fitness correlates of experimentally altered hatching asynchrony magnitude in chicks of a wild seabird.
abstract: Nest-bound chicks depend entirely on their parents for food, often leading to high sibling competition. Asynchronous hatching, resulting from the onset of incubation before clutch completion, facilitates the establishment of within-nest hierarchy, with younger chicks being subject to lower feeding and growth rates. Because social and nutritional stresses affect baseline stress hormone levels in birds, younger chicks are expected to have higher levels of corticosterone than their siblings. As previous studies showed that hatching asynchrony magnitude influences the course of sibling competition, it should also affect baseline corticosterone. We measured baseline corticosterone at age 5 days in nestling black-legged kittiwakes (Rissa tridactyla) in 3 types of experimental broods: synchronous, asynchronous, and highly asynchronous. Sexual dimorphism takes place during chick-rearing and might also influence baseline corticosterone, we thus included chick sex in our analyses and also monitored chick growth and survival. Baseline corticosterone did not differ among A-chicks, but was higher in B-chicks from highly asynchronous broods compared with the other brood types, in line with the presumed increase in nutritional stress. In asynchronous broods, A-chicks had higher baseline corticosterone than their siblings, contrary to our expectations. We interpret that result as a cost of dominance among A-chicks. In line with previous studies, mass gain was negatively correlated with baseline corticosterone levels. We found that baseline corticosterone predicted survival in a sex-specific way. Regardless of hatching rank, males with higher baseline corticosterone suffered higher mortality, suggesting that males were more sensitive to high level of stress, independently of its cause.
authors.affiliation: CNRS, UPS, ENFA, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), F-31062 Toulouse, France; Université Toulouse 3 Paul Sabatier, CNRS, ENFA, UMR5174 EDB, 118 Route de Narbonne, F-31062 Toulouse, France. Electronic address: thomasmerkling00@gmail.com.
authors.forename: Thomas
authors.initials: T
authors.lastname: Merkling
authors.affiliation: Centre d'Etudes Biologiques de Chizé, CNRS, 79360 Villiers en Bois, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Chastel
authors.affiliation: CNRS, UPS, ENFA, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), F-31062 Toulouse, France; Université Toulouse 3 Paul Sabatier, CNRS, ENFA, UMR5174 EDB, 118 Route de Narbonne, F-31062 Toulouse, France.
authors.forename: Pierrick
authors.initials: P
authors.lastname: Blanchard
authors.affiliation: Centre d'Etudes Biologiques de Chizé, CNRS, 79360 Villiers en Bois, France.
authors.forename: Colette
authors.initials: C
authors.lastname: Trouvé
authors.affiliation: U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, AK 99508, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Hatch
authors.affiliation: CNRS, UPS, ENFA, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), F-31062 Toulouse, France; Université Toulouse 3 Paul Sabatier, CNRS, ENFA, UMR5174 EDB, 118 Route de Narbonne, F-31062 Toulouse, France.
authors.forename: Etienne
authors.initials: E
authors.lastname: Danchin
mesh_terms: D000818:Animals; D001947:Breeding; D046091:Charadriiformes / Q000502:physiology*; D003345:Corticosterone / Q000097:blood; D005260:Female; D008297:Male; D009425:Nesting Behavior / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology*
chemical_list: D003345:Corticosterone
keywords: Aggression; Corticosterone; Hatching asynchrony; Sexual dimorphism; Sibling competition