Start date: Summer 2015
End date: Ongoing
Location: Fellsmere, Florida
Partner: Pelican Island Audubon Society
You may never have heard of Blue Cypress Lake, located in rural Central Florida, but it is suspected to be among the most popular nesting places for ospreys in North America. In 2015, Pelican Island Audubon Society, named for the first natural refuge established by President Theodore Roosevelt, received a grant to study the lake’s osprey population in order to better understand their nesting and migration.
PIAS members Dr. Richard Baker, Dr. Juanita Baker, Bob Bruce, Bill Loftus, and others surveyed the lake by kayak and collected GPS waypoints for each nest observed in the rings of cypress trees surrounding the lake. Each tree was marked with a metal tag and noted whether the nest was occupied and if there were already fledglings in it.
Upon receiving the data, I transformed the coordinate format to decimal degrees from standard degrees/minutes/seconds and imported into the open-source web mapping platform CARTO. I created a basic webmap displaying the location of each observed nest, color coded by occupancy status, overlaid upon the built-in satellite imagery basemap. Then in ArcGIS Desktop, we conducted density analysis of the nests along the shoreline by snapping the nests to the nearest segment of coastline and aggregating the number of nests per kilometer distance. This helped PIAS understand the pattern of distribution around the lake, which was heavily weighted to the Northwestern shore. Comparing against the distribution of vegetation data from the St. Johns Water Management District, part of the variation in nesting is explained by sections of shoreline with few or no trees, but the prevailing westerly winds and the presence of human settlement along the eastern shore may play a role as well. I also examined the distance between each nest and its closest tree using the Near tool, which allows PIAS to compare the spacing of nests to other osprey settlements to understand territoriality and other factors relating to nest site selection.
PIAS aims to make this a longitudinal study, with possible implications for detecting effects of global warming or increasing conservation protections for the birds in the area. PIAS are also interested in examining patterns of nest reuse vs. abandonment.