Human-made structures as nesting sites for hummingbirds across the Americas: insights from citizen science

Abstract Urbanization can negatively affect nesting and reproductive behaviors of birds. Even so, certain species can survive in abundance despite its negative impacts, due to their ability to use alternative human-made structures as nesting sites. There are several studies focusing on hummingbirds’ floral resource use in urban environments, however, little is known about their reproduction and nesting in these areas. Here, we used 5,136 nest photographic records from WikiAves and eBird , two widely used crowdsourcing citizen science platforms, to assess hummingbird nest site choice in natural and anthropized environments across the Americas. We found that 74 hummingbird species (32.03% of the sampled and 20.22% of known species) used diverse human-made substrates as nesting sites or built nests in anthropized environments. This use was observed across almost all clades and its detection was related to sampling effort, but not to species’ body mass, a trait often associated with hummingbird occurrence in urban areas. Overall, these results could indicate behavioral plasticity in some hummingbird species reproductive behavior and nesting resource use, besides their ability to incorporate novel floral resources and nectar feeders in their diet across human-modified areas. Because plants were their preferred nesting sites even in anthropized environments, the importance of maintaining vegetation in transformed and urbanized areas to support these pollinator populations is highlighted. Finally, our results also emphasize the potential of citizen science to provide large amounts of data across extensive geographical regions that would otherwise be difficult to obtain.