Meeting Abstract
It has long been assumed that a key determinant of reproductive success in birds is the quality of parental care and, consequently, increased foraging effort associated with rearing chicks. Some, though not all, studies have shown that parental effort, as measured by provisioning rate, can affect reproductive output although individuals appear to have considerable plasticity regarding provisioning rate, suggesting that perhaps individuals vary in the cost they pay for provisioning chicks at a higher rate. However, little is known about the physiological basis of individual variation in workload associated with foraging effort, or costs associated with high workload. To examine physiological response to increased workload, we experimentally manipulated foraging costs in captive zebra finches (Taeniopygia guttata) to examine physiological responses to “training” and high workload. We measured pre-treatment basal metabolic rate (BMR), hematocrit (Hct), and hemoglobin (Hb), and collected plasma samples (n=18 males, 17 females). Then we subjected half of the birds to high foraging cost conditions (HF) and the other birds to control foraging conditions (CTR). We measured BMR and collected plasma samples again at 3 timepoints over 90 days as birds adapted to HF condition. All birds were sacrificed at the end of the experiment to examine longer-term changes in body composition and physiology. Preliminary results showed that HF birds foraged at a higher rate, and that there was no change in BMR, Hct, Hb, pectoral muscle mass and heart mass, in relation to increased workload. Regarding potential physiological cost, HF birds had smaller gut size compared to CTR birds at day 90. To further examine physiological costs induced by high workload, we will analyze measures of oxidative stress and plasma metabolites.
