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In the city or country, dense vegetation is better for birds

April 5, 2012

Guest post by Kayla Garcia, Cornell Class of 2013

Animals are confronted with many new challenges as the globe becomes increasingly urbanized. For birds, urbanization may affect the food supply, the predator community, and the ability to find cover that offers protection from predators. Young birds that recently left the nest, in particular, suffer from high rates of mortality. Predation is a primary cause of fledgling mortality, and predator numbers tend to be greater in urbanized areas than in rural areas. Common predators of urban songbirds include raptors, domestic cats, raccoons, and unexpectedly for many, chipmunks.

In a recent study, researchers examined post-fledging survival across a rural-to-urban gradient at 26 sites in the Columbus, Ohio metropolitan area. The two bird species, Northern Cardinal (Cardinalis cardinalis) and Acadian Flycatcher (Empidonax virescens), were chosen because of their different nesting strategies: cardinals fledge at a younger, less mature age and often breed in urban environments, while flycatchers stay in the nest longer and are less likely to nest in urban areas. Radio transmitters were attached to fledgling birds and their survival and movements were tracked after fledging.

Northern Cardinal fledglings have a better chance at surviving if they can find dense cover in which to hide from predators. Photo by FeederWatcher Lisa Barker.

Somewhat surprisingly, the researchers found that overall survivorship was not strongly influenced by urbanization in either species. Further, cardinals were more likely to survive in more urbanized areas during the first three days post-fledging. Cardinals were also more likely to choose areas with more understory plant cover and fledglings were more likely to survive in areas with a dense understory. Because fledgling survival increases as the amount of understory vegetation increases, planting dense shrubs in suburban and urban yards will likely benefit the birds, even in highly urbanized landscapes.

For tips on how to create a more bird-friendly yard, visit the Cornell Lab of Ornithology’s new YardMap project.

Source: Ausprey, I. J., and A. D. Rodewald. 2011. Postfledging survivorship and habitat selection across a rural-to-urban landscape gradient. The Auk 128:293-302.

Kayla Garcia is a junior studying Natural Resources and Entomology at Cornell University. Her love for nature began with sneaking out of the house to watch alligators while growing up in central Florida, though now she mostly sticks to birds, smaller herps, and arthropods. In the future, she hopes to share her love and enthusiasm for the natural world in part through educational outreach and public service. When not holed up in one of Cornell’s many excellent libraries, Kayla enjoys making tortillas, exploring Ithaca, and puzzling over the poor hunting skills of her pet vinegaroon (a kind of scorpion), Waylon.

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