Blue Cypress Lake: an Osprey Paradise
Osprey Pandion haliaetus
by Bill Loftus, Ph.D.
On a calm, sunny morning in April, a small boat captained by Jim Shea leaves the dock at Blue Cypress Lake with three other Pelican Island Audubon members. Motoring out the boat channel onto the main lake, Jim turns the boat north along the outer fringe of cypress trees. With Jim, Donna Halleran, Dr. Richard Baker and I are conducting the latest annual census of Osprey nests around the lake. We began this count in 2014 when Dr. Baker suggested that the number of nests was greater than he had seen in the past. We felt it necessary to document the importance of this lake to Ospreys by obtaining an annual total count of nests. We are also concerned about the potential effects of bird flu on the Ospreys.
Blue Cypress Lake is not well-known even to Indian River County residents, yet this 3×5 mile: lake remains one of the most pristine water-bodies in Florida. It is surrounded by freshwater marshes and dense cypress/hardwood forests virtually unbroken but for a small fish camp, county park and village. Much of the virgin 100-500-year-old cypress trees were logged in the first half of the 20th century, leaving wide stumps behind. Luckily for the Ospreys, many of the smaller and misshapen trees that were less valuable as lumber were left in the lake. Changing conditions around the lake affected the birdlife; for example, field notes from 1927 detailed 125 active Wood Stork nests, whereas none are seen there today2. Later, the lake and some adjacent agricultural lands were preserved by the St. Johns River Water Management District as part of the river’s headwaters. Those former ag lands were reflooded to form shallow, nutrient-rich water-conservation areas, including the Stick Marsh, Headwater Lakes and Lake Garcia, to the east and northeast of the lake.
Drs. Richard and Juanita Baker1 counted 158 Osprey nests at the lake in 2002, a remarkable number considering that many lakes have only one or two nesting pairs of this territorial bird. Our first census in 2014 found 214 occupied nests, and from 2015 to 2019, we’ve counted between 288 to 329 occupied nests. When Covid-19 struck in 2020, Jim Shea boated alone and counted 291 nests. No count was done in 2021. We have nearly completed this year’s count which again promises to exceed 300 nests. These numbers are also a testament to the recovery of this species whose populations, like those of many raptors, declined precipitously from pesticide poisoning in the 1950s-60s.
Several raptor experts have told us that our Blue Cypress Lake probably has the highest nesting density of Osprey in the world –quite a distinction for this small lake! What factors account for this density? First, most of the cypress trees with nests are separated from the shoreline by water, affording the Osprey protection from predators like raccoons (alligators have a role here!). Similarly there is very little human disturbance of nesting birds on the lake. Secondly, the ag lands produce large numbers of Gizzard Shad, planktivorous fish that feeds both Osprey and Largemouth Bass. Most Osprey appear to feed in the marshes and bring back shad to the nests. It is this combination of protected and abundant nest sites coupled with a huge prey base that we believe explains the Blue Cypress phenomenon. Word has spread among birders and photographers about the Osprey, and many make special trips there to view the birds. Let’s continue to protect the lake and its birds so that they may continue to nest in safety for years to come.
References
- Baker, R. H. & J. N. Baker, 2017, Reflections of Blue Cypress 2nd Edition, Pelican Island Audubon Society.
- Howell, A. H. ,1932, Florida Bird Life. Florida Department of Game and Fresh Water Fish Commission in Cooperation with the Bureau of Biological Survey, U.S. Department of Agriculture, New York: Coward-McCann, Inc.