title: Linking pre-laying energy allocation and timing of breeding in a migratory arctic raptor.
abstract: For migratory species, acquisition and allocation of energy after arrival on the breeding grounds largely determine reproductive decisions. Few studies have investigated underlying physiological mechanisms driving variation in breeding phenology so far. We linked physiological state to individual timing of breeding in pre-laying arctic-nesting female peregrine falcons (Falco peregrinus tundrius). We captured females from two populations 2-20 days before egg-laying to assess plasma concentration of β-hydroxybutyric acid (BUTY) and triglyceride (TRIG), two metabolites known to reflect short-term changes in fasting and fattening rate, respectively. We also assessed baseline corticosterone (CORTb), a hormone that mediates energy allocation, and the scaled mass index (SMI) as an indicator of somatic body reserves. Plasma BUTY was slightly higher during the pre-recruiting period compared to the period of rapid follicular growth, indicating a reduction in catabolism of lipid reserves before investment in follicle development. Conversely, TRIG levels increased in pre-recruiting females, and best-predicted individual variation in pre-laying interval and lay date. A marked increase in CORTb occurred concomitantly with the onset of rapid follicle growth. SMI was highly variable possibly reflecting variation in food availability or individuals at different stages. Results suggest that (1) lower rates of pre-laying fattening and/or lower mobilization rate of lipoproteins to ovarian follicles delayed laying, and (2) an elevation in pre-laying CORTb may result from, or be required to compensate for, the energetic costs of egg production. Results of this study illustrate how variation in the allocation of energy before laying can influence individual fitness-related reproductive decisions.
authors.affiliation: Département de biologie, chimie et géographie et Centre d'études nordiques, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, QC, G5L 3A1, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Lamarre
authors.affiliation: Arctic Raptors Project, Box 626, Rankin Inlet, NU, X0C 0G0, Canada. alastair.franke@ualberta.ca.
authors.forename: Alastair
authors.initials: A
authors.lastname: Franke
authors.affiliation: Department of Biological Sciences and Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, N9B 3P4, Canada.
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Love
authors.affiliation: Département de biologie, chimie et géographie et Centre d'études nordiques, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, QC, G5L 3A1, Canada. legagneux@gmail.com.
authors.forename: Pierre
authors.initials: P
authors.lastname: Legagneux
authors.affiliation: Département de biologie, chimie et géographie et Centre d'études nordiques, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, QC, G5L 3A1, Canada.
authors.forename: Joël
authors.initials: J
authors.lastname: Bêty
mesh_terms: D000818:Animals; D001110:Arctic Regions; D001947:Breeding; D003345:Corticosterone; D020304:Raptors; D012098:Reproduction
chemical_list: D003345:Corticosterone
keywords: Corticosterone; Energy allocation; Peregrine falcon; Triglyceride; β-Hydroxybutyric acid