Doctor of Philosophy (PhD)
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Predators are often the focus of conservation efforts. They can be useful sentinel species, umbrella species, and flagship species. Predators can also be the first guild lost when ecosystems are under stress, especially from anthropogenic land-use change. Avian predators (raptors) can be an exception to this trend, filling the role of apex predators across the urban gradient. South Florida contains the Everglades ecosystem and one of the fastest growing human populations in the country. In the current study, I investigated the population dynamics of South Florida’s most abundant hawk: the Red-shouldered Hawk (Buteo lineatus, RSHA) across the urban gradient.
South Florida is home to its own subspecies of RSHA (Buteo lineatus extimus), which has heretofore received little formal study. I first observed breeding attempts to quantify the productivity of the southern subspecies. South Florida RSHAs were found to be equally productive in urban and exurban areas and produced 1.8 ± 0.6 fledglings per successful nest, about average for this species. I developed habitat maps around each nest using remote sensing, but land cover was not related to the likelihood of nest success.
I then placed cameras in nests to observe the prey items fed to chicks. Adults fed primarily reptiles (58%) and amphibians (18%). I also partnered with three wildlife rehabilitation hospitals to screen RSHAs that perished in their care for anticoagulant rodenticides (ARs). The Environmental Protection Agency restricted the sale of ARs to the public in 2008 in part to reduce secondary poisoning to wildlife like raptors. Despite these restrictions and the low rate of mammal consumption among local birds, 49% of RSHAs screened had been exposed to ARs.
Finally, I investigated the genetic diversity of RSHAs and found evidence for a genetic bottleneck, reduced genetic diversity, and inbreeding in the focal population. My study found RSHAs in South Florida to be very flexible in their diet and nest sites but also found reduced genetic diversity and high rates of exposure to toxins. Additional research is needed to determine whether the population is increasing, stable, or declining in the rapidly urbanizing region.
Marain, Donna, "Investigating The Population Dynamics of an Avian Apex Predator Across an Urban Gradient" (2020). FIU Electronic Theses and Dissertations. 4568.
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