title: Neonatal body condition, immune responsiveness, and hematocrit predict longevity in a wild bird population.
abstract: Measures of body condition, immune function, and hematological health are widely used in ecological studies of vertebrate populations, predicated on the assumption that these traits are linked to fitness. However, compelling evidence that these traits actually predict long-term survival and reproductive success among individuals in the wild is lacking. Here, we show that body condition (i.e., size-adjusted body mass) and cutaneous immune responsiveness to phytohaemagglutinin (PHA) injection among neonates positively predict recruitment and subsequent longevity in a wild, migratory population of house wrens (Troglodytes aedon). However, neonates with intermediate hematocrit had the highest recruitment and longevity. Neonates with the highest PHA responsiveness and intermediate hematocrit prior to independence eventually produced the most offspring during their lifetime breeding on the study site. Importantly, the effects of PHA responsiveness and hematocrit were revealed while controlling for variation in body condition, sex, and environmental variation. Thus, our data demonstrate that body condition, cutaneous immune responsiveness, and hematocrit as a neonate are associated with individual fitness. Although hematocrit's effect is more complex than traditionally thought, our results suggest a previously underappreciated role for this trait in influencing survival in the wild.
authors.affiliation: Behavior, Ecology, Evolution, and Systematics Section, School of Biological Sciences, Illinois State University, Normal, IL, USA.
authors.forename: E Keith
authors.initials: EK
authors.lastname: Bowers
authors.affiliation: Behavior, Ecology, Evolution, and Systematics Section, School of Biological Sciences, Illinois State University, Normal, IL, USA.
authors.forename: Christine J
authors.initials: CJ
authors.lastname: Hodges
authors.affiliation: Behavior, Ecology, Evolution, and Systematics Section, School of Biological Sciences, Illinois State University, Normal, IL, USA.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Forsman
authors.affiliation: Behavior, Ecology, Evolution, and Systematics Section, School of Biological Sciences, Illinois State University, Normal, IL, USA.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Vogel
authors.affiliation: Department of Biological Sciences, Towson University, Towson, MD 21252 USA.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Masters
authors.affiliation: Department of Biological Sciences, Towson University, Towson, MD 21252 USA.
authors.forename: Bonnie G P
authors.initials: BG
authors.lastname: Johnson
authors.affiliation: Department of Biological Sciences, Towson University, Towson, MD 21252 USA.
authors.forename: L Scott
authors.initials: LS
authors.lastname: Johnson
authors.affiliation: Behavior, Ecology, Evolution, and Systematics Section, School of Biological Sciences, Illinois State University, Normal, IL, USA.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Thompson
authors.affiliation: Behavior, Ecology, Evolution, and Systematics Section, School of Biological Sciences, Illinois State University, Normal, IL, USA.
authors.forename: Scott K
authors.initials: SK
authors.lastname: Sakaluk
keywords: Troglodytes aedon; fitness; phytohaemagglutinin; recruitment; survival