Recent research highlights the widespread promiscuity observed in birds. A comprehensive review, encompassing 342 species, discovered that approximately 75% of birds engage in extrapair copulations, involving one or more additional partners besides their nest mate.

The motivations behind avian infidelity remain elusive, yet various studies suggest that supplemental feeding can mitigate such behavior in certain species, exemplified by house sparrows. This suggests that providing food to birds might induce behavioral changes and potentially influence genetic diversity within urban populations.

For birds serving as pollinators, such as hummingbirds and lorikeets, there is evidence indicating that offering sugar water—mimicking the nectar they extract from plants—may lead to a reduction in their visits to native plants. Consequently, this could result in diminished pollen transfer. Given the prevalence of bird feeding in densely populated urban areas, the overall impact on such behavior remains uncertain.
Certain bird populations rely entirely on feeding to endure harsh winter conditions. For instance, Anna’s hummingbirds in British Columbia heavily depend on heated feeders. In contrast, some species, like hummingbirds in the southwest U.S., have experienced local abundance. Northern cardinals and American goldfinches have expanded their ranges northward, driven by the availability of food.

Remarkably, garden feeders have played a pivotal role in establishing a new wintering population of migratory blackcaps in the United Kingdom. This group has now evolved into a genetically distinct population compared to its counterparts, which typically migrate southward to Mediterranean wintering grounds.