Texas State University hummingbird study measures impact of urbanization

Travis Audubon recently learned of an interesting thesis completed by Texas State University graduate student Caley Zuzula. Caley, who received a master’s degree in Population and Conservation Biology in December, researched the effects of urbanization on hummingbird distribution.

Urbanization has led to a loss of natural habitat, an increase in impervious surfaces such as asphalt and concrete, and subsequently, an increase in the provisioning of food sources for local wildlife. One common scenario of supplementary feeding includes artificial nectar feeders for hummingbirds, which can be so successful at attracting hummingbirds as to cause an increase in local abundance past what could naturally occur.

While previous studies have investigated persistence of hummingbird populations across an urban-rural gradient, mine is the first to use artificial nectar removal from hummingbird feeders as a reliable measure of relative hummingbird abundance in the area surrounding each feeder. I deployed nectar feeders in locations encompassing various intensities of urbanization around San Marcos, Texas, to determine whether urbanization affects the relative abundance of black-chinned hummingbirds (Archilochus alexandri) and ruby-throated hummingbirds (Archilochus colubris) within 100, 200, and 400 meter distances from the feeders.

Figure 1 Solution (artificial nectar) consumption at each feeder location around the San Marcos, Texas, area. Larger dots indicate greater quantities of artificial nectar consumed.

Urbanization had a negative and significant effect on artificial nectar consumption across all three spatial scales, indicating that hummingbirds are less abundant in areas of greater urban intensity. In addition to developing a reliable new method for surveying hummingbirds, my findings show that urbanization, despite warmer local temperatures and increased food provisioning, may negatively affect some hummingbird populations.