title: Weathering the storm: parental effort and experimental manipulation of stress hormones predict brood survival.
abstract: BACKGROUND
  Unpredictable and inclement weather is increasing in strength and frequency, challenging organisms to respond adaptively. One way in which animals respond to environmental challenges is through the secretion of glucocorticoid stress hormones. These hormones mobilize energy stores and suppress non-essential physiological and behavioral processes until the challenge passes. To investigate the effects of glucocorticoids on reproductive decisions, we experimentally increased corticosterone levels (the primary glucocorticoid in birds) in free-living female tree swallows, Tachycineta bicolor, during the chick-rearing stage. Due to an unprecedented cold and wet breeding season, 90 % of the nests in our study population failed, which created a unique opportunity to test how challenging environmental conditions interact with the physiological mechanisms underlying life-history trade-offs.
  
  
  RESULTS
  We found that exogenous corticosterone influenced the regulation of parental decisions in a context-dependent manner. Control and corticosterone-treated females had similar brood failure rates under unfavorable conditions (cold and rainy weather), but corticosterone treatment hastened brood mortality under more favorable conditions. Higher female nest provisioning rates prior to implantation were associated with increased probability of brood survival for treatment and control groups. However, higher pre-treatment male provisioning rates were associated with increased survival probability in the control group, but not the corticosterone-treated group.
  
  
  CONCLUSIONS
  These findings reveal complex interactions between weather, female physiological state, and partner parental investment. Our results also demonstrate a causal relationship between corticosterone concentrations and individual reproductive behaviors, and point to a mechanism for why naturally disturbed populations, which experience multiple stressors, could be more susceptible and unable to respond adaptively to changing environmental conditions.
authors.affiliation: Department of Biological Sciences, Virginia Tech, Blacksburg, USA. j.ouyang@nioo.knaw.nl.|Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands. j.ouyang@nioo.knaw.nl.|Present address: NIOO-KNAW, P.O.Box 50, , 6700 AB, Wageningen, The Netherlands. j.ouyang@nioo.knaw.nl.
authors.forename: J Q
authors.initials: JQ
authors.lastname: Ouyang
authors.affiliation: Department of Biological Sciences, Virginia Tech, Blacksburg, USA.|Department of Evolutionary Zoology and Human Biology, University of Debrecen, Debrecen, Hungary.
authors.forename: Áz
authors.initials: Á
authors.lastname: Lendvai
authors.affiliation: Department of Zoology, University of British Columbia, Victoria, BC, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Dakin
authors.affiliation: Department of Biology, Queen's University, Kingston, Canada.
authors.forename: A D
authors.initials: AD
authors.lastname: Domalik
authors.affiliation: Department of Biology, Bucknell University, Lewisburg, USA.
authors.forename: V J
authors.initials: VJ
authors.lastname: Fasanello
authors.affiliation: Department of Biology, Bucknell University, Lewisburg, USA.
authors.forename: B G
authors.initials: BG
authors.lastname: Vassallo
authors.affiliation: Department of Biology, Bucknell University, Lewisburg, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Haussmann
authors.affiliation: Department of Biological Sciences, Virginia Tech, Blacksburg, USA.
authors.forename: I T
authors.initials: IT
authors.lastname: Moore
authors.affiliation: Department of Biological Sciences, Virginia Tech, Blacksburg, USA.|Department of Biology, Queen's University, Kingston, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Bonier
mesh_terms: D000818:Animals; D005260:Female; D005938:Glucocorticoids / Q000097:blood; D008297:Male; D046109:Passeriformes / Q000097:blood / Q000254:growth & development / Q000502:physiology*; D012098:Reproduction; D012621:Seasons; D013312:Stress, Physiological; D014887:Weather
chemical_list: D005938:Glucocorticoids