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Abstract

In 2012, the critically endangered Florida Grasshopper Sparrow (Ammodramus savannarum floridanus) was known to exist only on three public conservation areas with native dry prairie habitat. In 2013, an additional site was discovered on a grazed, semi-improved cattle ranch in Osceola County, Florida, USA (hereafter the Ranch). We describe initial results from an effort to establish a long-term demographic monitoring program at the Ranch (2014–2016). Band-resighting data revealed that the Ranch supported a minimum population of 29 territorial males in 2015 and 19 in 2016, representing 39% and 34% of the known wild male population, respectively. The weighted mean for apparent annual survival was 8% for fledged nestlings, 38% for independent fledglings, and 58% for adult males. High rates of nest loss to red imported fire ants (Solenopsis invicta) and other predators resulted in very low reproductive success and an estimated productivity of 1.66 young per pair in 2015. During 2013–2016, we documented 10 long-distance dispersal events (range = 12–25 km) for five adult males between the Ranch and other populations. All dispersing males appeared to be unpaired, and several males returned to the Ranch after their initial dispersal, suggesting the movements may have been forays by unpaired individuals searching for females. More extensive monitoring on the Ranch could help determine whether unbanded sparrows detected at the site each spring are locally produced or immigrants from other populations. Regardless, because of the size of the population and its central location, the Ranch supports species recovery goals of redundancy, resiliency, and connectivity. We discuss potential management challenges for this population, including high rates of nest failure.

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