Temperature-Related Changes in Avian Nestling Provisioning: A Global Analysis

Temperature-related changes in behaviour can negatively affect population persistence. One way in which species may be affected is in their ability to provide parental care: if parents are constrained, either physiologically or due to food limitation to provision nestlings, offspring development and survival may be impacted. Empirical studies have shown temperature-related changes in nestling provisioning in some, but not other species, yet the reason for this difference among species remains unclear. To predict the consequences of global change, it is important to understand what makes a particular species vulnerable to temperature-induced changes in parental care. Here, we used 47 effect sizes from published studies that quantified the relationship between ambient temperature and nestling provisioning rate in 39 bird species to determine how latitude, climate, breeding system, nestling diet and body mass explain variation in this relationship. Across all species, nestling provisioning rate was negatively correlated with temperature, regardless of latitude or breeding climate. Cooperative breeders provisioned less when temperatures rose, which contradicts prevailing predictions that helpers can mitigate adverse conditions but may also be because helpers can compensate when conditions become more suitable. This pattern was different in species with biparental care, which showed a wider range of responses. Moreover, provisioning was more impacted by temperature in larger-bodied species and in species with offspring that are not exclusively insectivorous, presumably either because food is more difficult to collect or because the energetic costs of provisioning are higher when it is warmer. Unless reduced provisioning is offset by higher quality food, parents apparently do not systematically buffer the effects of increased temperature, leaving nestlings to carry the costs. Knowing which characteristics make birds vulnerable to increasing temperatures can help in shaping future studies of climate change ecology and predicting differential effects of climate change on avian populations on a global scale.