Meeting Abstract
Body condition at life-history transitions, or “developmental milestones”, is known to affect fitness across a wide range of taxa. In passerines, the immediate post-fledging stage is marked by high levels of mortality and the transition from sedentary nestling to free-flying fledgling might therefore be a critical determinant of fitness. Numerous studies have shown positive relationships between somatic development (nestling mass or growth) and survival but very little is known about the physiological components of chick quality or phenotype at fledging. Here we present data on individual variation in a range of hematological measures (hematocrit, hemoglobin, and proportion of young red blood cells or reticulocytes) in European Starling chicks (Sturnus vulgaris) just prior to, and at the fledging stage (day 17 and day 21, post-hatch). Since there are well-documented “cohort” effects in offspring survival we first test for annual variation in hematological traits (relative to values in adults), and somatic development across three years (2013-2015) which varied in breeding productivity. Second, since post-fledging survival decreases with hatch date we compare physiological development of hematology for chicks in 1st and 2nd broods. Preliminary analysis shows a) rapid increase in hematocrit and hemoglobin and rapid decrease in proportion of reticulocytes just before fledging, b) lower hematocrit, hemoglobin, and reticulocyte levels in second brood chicks compared to first brood chicks, c) lower hematocrit, hemoglobin, and reticulocyte levels in years with lower overall breeding success. Our ultimate goal is to understand how the individual variation in hematology of chicks and fledglings might relate to the inter-annual variation in reproductive success.
