title: Experimental and observational studies of seasonal interactions between overlapping life history stages in a migratory bird.
abstract: Prior to reproduction, migratory animals are at the juxtaposition of three life history stages in which they must finish the non-breeding stage, initiate and complete migration, and prepare for the onset of breeding. However, how these stages interact with one another is not fully understood. We provide evidence that, for migratory birds that begin breeding development prior to departure from non-breeding sites, the level of breeding preparation can drive migration phenology, a critical behavioral determinant of reproductive success. Specifically, male American redstart (Setophaga ruticilla) plasma androgen levels, which increase in males during the period leading into migration, were positively correlated with energetic condition. We empirically tested the hypothesis that elevated androgen simultaneously supports migratory and breeding preparation in a hormone manipulation field experiment. Males with testosterone implants showed advanced preparation for migration and breeding, and ultimately departed on migration earlier than controls. It is assumed that early departure leads to early arrival at breeding areas, which increases breeding success. Collectively, our observational and experimental results demonstrate how overlapping life history stages can interact to influence important components of an individual's fitness. This highlights the critical need for understanding population processes across the full life cycle of an organism to better understand the ecological and evolutionary origins of complex life history events.
authors.affiliation: School of Biology and Ecology, University of Maine, Orono, ME, USA; Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA. Electronic address: TonraC@si.edu.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Tonra
authors.forename: Peter P
authors.initials: PP
authors.lastname: Marra
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Holberton
mesh_terms: D000367:Age Factors; D000728:Androgens / Q000097:blood; D032761:Animal Experimentation; D025041:Animal Migration / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D004343:Drug Implants; D017753:Ecosystem; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D005260:Female; D008297:Male; D046109:Passeriformes / Q000502:physiology*; D012098:Reproduction / Q000187:drug effects / Q000502:physiology*; D012621:Seasons; D012741:Sexual Maturation / Q000187:drug effects / Q000502:physiology*; D013739:Testosterone / Q000008:administration & dosage
chemical_list: D000728:Androgens; D004343:Drug Implants; D013739:Testosterone
keywords: American redstart; Carry-over effects; Departure timing; Migration; Setophaga ruticilla; Testosterone