Meeting Abstract

55.8  Sunday, Jan. 5 15:15  Physiological Components of Chick Quality at a Critical Life History Transition CORNELL, A.E.*; WILLIAMS, T.D.; Simon Fraser University; Simon Fraser University acornell@sfu.ca

In passerines, the immediate post-fledging stage is marked by high levels of mortality, making the developmental “milestone” from nestling to fledgling a critical life history transition. Although many studies have shown positive relationships between nestling mass and survival, other physiological components of chick quality or phenotype at fledging have rarely been studied. Here we present data on individual variation in a range of key physiological components of ‘condition’ or quality at fledging that might determine post-fledging survival in European Starling chicks (Sturnus vulgaris) just prior to, and at the fledging stage (day 17 and day 21, post-hatch). We measured hematocrit, hemoglobin, reticulocyte counts, oxidative stress, feather length, and body mass, as indices of oxygen carrying capacity, red blood cell production, oxidative imbalance, feather growth rate, and overall functional maturation, respectively. We focus on comparison of physiological ‘quality’ of chicks from first versus second brood, because second brood offspring are known to have lower post-fledging survival and recruitment. Preliminary analysis shows a) rapid increase in hematocrit and hemoglobin just before fledging, even though mean trait values at fledging remain lower than adult values, b) lower hematocrit, hemoglobin, and body mass in second versus first brood chicks, and c) an average decrease in total mass just before fledging which is greater in first broods (5.7% versus 0.7%). Our long-term goal is to relate individual variation in physiological quality of chicks to flight performance (measured at fledging in a flight chamber) as a putative index of fitness.