Sex-Dependent Reproductive Outcomes in Adult and Developmentally Lead (Pb) Exposed Zebra Finches

Lead (Pb), an environmental heavy metal contaminant, is an ongoing threat to urban songbird populations. While prior studies have found deleterious effects of developmental exposure to Pb on adult fitness in zebra finches (Taeniopygia guttata), there is ambiguity in the direct vs. indirect impact of Pb on developmental mortality. Pb’s impacts on reproductive success across a population have not been investigated in a multigenerational study which would elucidate the true threshold for existential levels of Pb exposure, assuming not all individuals need to receive the highest exposure level for across the board effects. We quantified the reproductive productivity and parenting success of two generations of Pb-exposed and control birds. In the first-generation, birds were exposed to Pb in drinking water once they were sexually mature. The offspring from this first-generation were exposed from conception through to sexual maturity. That second generation of birds were then arranged in breeding rooms with equal ratios of Pb-exposed and Control males and females to allow for mixed treatment pairings, if they occurred. Our preliminary results suggest stark differences in offspring mortality between generations. When a population is first exposed to Pb reproduction is suppressed by approximately 30% but mortality is not affected. When the developmental exposed offspring of that parent generation reproduce, the 60% suppression of reproduction and increase in mortality is sex dependent. Differences in outcomes were not found when the male (compared with the female) parent was exposed to Pb. These results suggest that the behavioral impact of Pb exposure (specifically an apparent failure to perform normal parenting tasks) during development is more pronounced than the direct physiological impact.