Evolution and Ecology of Urban Pigeons (Columba livia) in Northeastern North America
Urbanization is drastically changing landscapes across the globe leading to changes in the ecological and evolutionary dynamics within cities. This urban landscape change may restrict, facilitate, or have no effect on gene flow, depending on the organism and extent of urbanization. In human commensals, with high dispersal ability, urbanization can facilitate gene flow by providing continuous suitable habitat across a wide range. Additionally, suburban or rural areas with lower human population density may act as a barrier to gene flow for these human commensals. Spatial population genetic approaches provide a means to understand genetic connectivity across geographically expansive areas that encompass multiple metropolitan areas. Here, I examined the spatial genetic patterns of feral pigeons (Columba livia) living in cities in the Northeastern United States. I focused my sampling on the Northeastern megacity, which is a region covering six large cities (Boston, Providence, New York City, Philadelphia, Baltimore, and Washington, DC). I performed ddRAD‐Seq on 473 samples. My analysis detected higher‐than‐expected gene flow under an isolation by distance model within each city. I conclude that the extreme urbanization characteristic of the Northeastern megacity is likely facilitating gene flow in pigeons. Additionally, spatial genetic patterns may diverge between cities as food accessibility, nesting site availability, and eradication policies differ. Pigeon hobbyists (people who collect, breed, trade, and race pigeons) also vary by region leading to differing degrees of public tolerance for pigeons and impacting the spatial genetic patterns. Fancy and racing pigeons display a variety of characters which are often seen in the feral population, suggesting that these breeds may partially contribute to feral populations. I found that pigeon population structure is influenced by continued introduction of racing/fancy pigeons and the local conditions including attitudes towards pigeons, management practices, and food availability. Furthermore, variation in behavioral traits is especially important in novel habitats where selection forces determine successful colonizers. Prey species must constantly balance the risk versus reward of remaining in an area with threats while gaining possible fitness benefits. Flight initiation distance, the distance at which an animal flees when approached by a human, is a common metric used to assess habituation to stressors and risk behavior. I examined the flight initiation distance of pigeons across New York City, USA. I then assessed this behavioral response across the landscape with respect to multiple urbanization factors related to human activity, the abiotic environment, and the ecological community. I found that flight initiation distance in pigeons decreased with increased human activity demonstrating that pigeon behavior varies with urbanization, human activity, and ecological attributes. Since behavioral changes are often the most rapid phenotypic response to change, this study demonstrates that pigeons are responding to anthropogenic stressors, which may set the stage for adaptive changes. Overall this research demonstrates that urban landscape heterogeneity may contribute to variable spatial genetic and behavioral responses across a single city, therefore researchers must examine patters at different spatial scales. Moreover, organisms such as pigeons that depend on humans, exhibit fine-scale spatial genetic structure that reflects human patterns and distributions, stressing the importance of sampling across urban areas.
Biology|Ecology|Evolution and Development|Zoology
Carlen, Elizabeth Jane, "Evolution and Ecology of Urban Pigeons (Columba livia) in Northeastern North America" (2021). ETD Collection for Fordham University. AAI28495279.