Meeting Abstract
Parental care increases fitness, but it can also be energetically taxing. In species with biparental care, dissimilarity in parental care may require that one individual of the pair provide a majority of the workload. The stress response evolved to allow animals to cope with energetic needs when facing a stressor, and thus is likely an important mediator of parental care. In birds, leukocyte counts, specifically the ratio of heterophils to lymphocytes, can be a reliable proxy for stress. In addition, because leukocyte numbers do not change as rapidly as hormonal measures of stress, H/L ratios are proposed to represent prolonged stress. Such a measurement might be more meaningful in relation to parental care, which is ongoing during the nestling period. We determined relationships among parental care, stress, and reproductive success. We also determined if parental pairs were similar or dissimilar in care behaviors. We predicted that individuals that provided more parental care to offspring would have higher H/L ratios. We also predicted H/L ratios would be negatively correlated with reproductive success. Finally, we predicted that H/L ratios would be higher and reproductive success would be lower for pairs that were dissimilar. Using House Wrens (Troglodytes aedon), we determined H/L ratios in blood smears from adult birds. When nestlings were 4-6 days post-hatch, we recorded parental care videos to determine male and female nest visits rates and pair similarity. We weighed nestlings when they were 4, 8, and 10 days post-hatch and determined fledging success as measures of reproductive success. We discuss our findings within the context of long-term stress and parental care.
