Birds in urban ecosystems: Population dynamics, community structure, biodiversity, and conservation

With the global high rate of urbanization and the rapid loss of wild habitat land, cities are now viewed as challenging ecosystems for sustaining biotic communities and rich diversity. During the 2000s research on urban bird populations and communities focused on global patterns, as well as processes and mechanisms that lead to the two globally recognized patterns: increased overall population densities and decrease in species diversity compared with wildlands. Birds adapt to the urban ecosystem both physiologically (changes in stress hormones), and behaviorally (e.g., changes in foraging behavior, extending the breeding season). The increase in population density is related to the increase in food abundance, and probably to the reduction in predation pressure. The loss of diversity is related to loss of habitat, the high human density, and negative interactions with synanthropic species. Recognizing that the urban habitat will continue to grow, efforts to turn the city into a more friendly habitat for a variety of bird species should focus not only on habitat and vegetation structure, but also on niche opening for subordinate species, by excluding locally aggressive, synanthropic species.