Meeting Abstract
One of the key determinants of reproductive success in birds is the quality of parental care and, thus, increased foraging effort associated with rearing chicks. However, there appears to be large individual variation in parental effort, suggesting that individuals vary in the cost they pay for “working hard”. Additionally, costs of activity can often be deferred from one life-history stage to a later stage (i.e. carry-over effects). Although some studies have found that increased workload negatively affects reproduction and survival, little is known about the physiological mechanisms underlying carryover costs associated with high workload. We experimentally manipulated foraging effort in captive zebra finches ( Taeniopygia guttata) to examine how high workload affects energy expenditure, oxidative stress and reproductive output. During phase 1 of the experiment, birds were subjected to either, a) a high foraging cost treatment (HF; feeders suspended from the cage roof with no perches) or b) control foraging conditions (CTRL) for 2 weeks, after which all birds were paired for breeding under common-garden CTRL conditions. During phase 2 of the experiment, HF birds were again housed and trained in the HF treatment and were then paired for breeding while being kept in the same HF condition. CTRL birds were given regular feeders throughout the experiment. Blood samples were collected at multiple time points to assess daily energy expenditure (using doubly-labeled water) and oxidative stress. Breeding propensity, egg and clutch size, and breeding productivity were assessed for both reproductive attempts. We predicted that HF birds would have lower reproductive output and have higher daily energy expenditure and oxidative stress than CTRL birds.
