Anthropogenic nest material use correlates with human landscape modifications in a global sample of birds

As humans increasingly modify the natural world, many animals have responded by changing their behaviour. Predicting the extent of these responses is a key step in conserving these species. For example, the tendency for some species of birds to incorporate anthropogenic items - particularly plastic material - into their nests is of increasing concern, as in some cases this behaviour has harmful effects on both adults and young. Studies of this phenomenon, however, have to date been limited in geographic and taxonomic scope. To investigate the global correlates of anthropogenic (including plastic) nest material use, we used Bayesian phylogenetic mixed models and a dataset of recorded nest materials in 6,147 species of birds. We find that after controlling for research effort, anthropogenic nest material use is correlated with proximity to human landscape modification, synanthropic (artificial) nesting locations, breeding environment, and the number of materials that has been recorded within the species nest. We also demonstrate that anthropogenic nest material use is unrelated to body mass, range size, or conservation status. These results indicate that anthropogenic materials are more likely to be included in nests when they are more readily available, as well as potentially by species who have more flexibility in nest material choice.