COS 165-3 - Land cover conversion to agriculture and temperature extremes synergistically erode avian reproductive success across the continental United States

Background/Question/Methods

Habitat loss to anthropogenic disturbance is the primary driver of species loss and endangerment. Efforts to increase biodiversity in working landscapes, such as installing nest boxes for cavity-nesting birds, may allow more species to thrive in human-dominated landscapes. However, as climate change progresses, human-dominated landscapes may expose birds to new temperature extremes because converting land to agriculture removes trees that insulate the understory from ambient temperature. In bird species with altricial young, nestlings are ectothermic, so both low and high temperatures divert energy from growth to thermoregulation. The lethal effects of cold are well-documented, but the effects of heat will also be salient in the future as climate change increases both mean and maximum temperatures. We leveraged Cornell University’s Nestwatch database, which documents 317,147 nests of 287 species over 24 years and 92,896 unique locations and the UC Merced gridMET database to explore how temperature extremes and land use interact to affect nest success.

Results/Conclusions

We found that, across species and geography, bird nests in agricultural areas are more likely to fail during temperature spikes than those in forest. Indeed, success rates increased with temperature spikes in forested areas, suggesting that birds nesting in or near forest might be more resilient to future increases in temperature than birds nesting in human-dominated areas. In addition, we used a set of MACA-downscaled Global Climate Models (GCMs) to compare future success among land use types. We found that future nests in agriculture are likely to be less successful than past nests. In contrast, we found that future nests in forest have a similar probability of success as past nests. Retaining forest in agricultural landscapes may be an effective conservation strategy to prevent the loss of more species to habitat loss and climate change.