Osprey Population On Sanibel Island, Florida
1978-2003 Increased 400%
The author, Peter Wallack, is now working on TIOF’s archives. Most of this article is based on interviews with Tim Gardner, present President of TIOF, and Mark “Bird” Westall, founder and first President of TIOF. Peter Wallack is on Sanibel Captiva Conservation Foundation’s Education Committee and has contributed curriculum extensions for their 14 Educational units that enhance the school classroom follow through of their SCCF experiences. Peter Wallack is retired after 34 years as an academic and teacher of World Cultures.; the hundreds of images there are free for educational use by individuals, non-profit environmental and bird organizations, government organizations, universities, museums, state parks and schools.
In the post war era farm production knew no limitations; if the pesticide DDT was good for protecting crops than at eight cents a pound why not put tons of it on every field to really protect them. The fact that this poison would wash off the land and accumulate in fish fat which in turn would lead to the thinning of the egg shells and the endangerment of Osprey, Bald Eagles as well as wading and other birds which ate fish was first warned about by Rachel Carson In SILENT SPRINGS, 1962. It took a decade before DDT use was made illegal by a product manager of the newly formed Environmental protection Agency; that manager was The International Osprey Foundation’s present President, Tim Gardner.During that post war period up until the banning of DDT in 1972 Sanibel Island was, as today, fifty percent J.N. Ding Darling National Wildlife Refuge and another 35 percent City designated wetlands not suited for development or Sanibel Captiva onservation Foundation preserves and greenways along the Bicycle Paths. There were probably just several dozen Ospreys on Sanibel then.
In 1974 the first Osprey platform on Sanibel was built in Ding Darling National Wildlife Refuge at the seven-tenths mile marker on the left. Between 1974 and 1980 about 6 to 8 platforms were put up a year on city land, private property, Ding Darling land, Sanibel Captiva Conservation Foundation land, and on Lee County Electric Company utility pole tops. Charles Lebuff, of the U.S. Fish and Wildlife Service at Ding Darling NWR, and George Campbell, a local naturalist, led this effort. Osprey before that era had created electrical outages as they themselves were sometimes electrocuted when they built nests on the poles to be over the tree canopies to have the instinctual view they needed for protecting their young and spotting prey. Lee County Electric Company before 1974 had ripped down Osprey nests as nuisances; then George Campbell enlightened Lee County Electric and got them started on building Osprey platforms for both the good of the birds and the electric service on Sanibel.
The first accurate Osprey nest and territory count was conducted by Mark “Bird” Westall in 1979 with the use of an airplane to search out all active nests on the Island many of which can not be seen by man since they are away from the roads buffered by nearby woods and wetlands. In 1979 there were 35 active nests with a possible and probable range of 60 to 100 Ospreys. Today TIOF monitors all the Osprey nests with six teams of volunteers. There are between 320 and 400 Osprey now on Sanibel. That is a 400 % increase in 25 years.In the past Mangroves with their even canopy tops were not attractive sites for Osprey nests. Today many new generations of Osprey born on Sanibel use mangrove sites from eight feet off the water to dead trees from ten to twenty feet below the canopy.
A high-density shallow water area with a big food source at Clam Bayou has established the adaptability of the Osprey to live in the dozens all within six hundred yards of each other. It was my privilege to be escorted on Clam Bayou to see this first hand with Tim Gardner escorting me in his flat boat in that bayou; Tim lives right on Clam Bayou. Bird Westall believes that Osprey flying by looking for new territories, as pressure by man’s use of their habitats and their own increasing populations forced them to search out new nesting sites, opened up many Osprey eyes to observing the good life of Sanibel Osprey. Based on these observations, Bird Westall believes the Osprey migrants are then capable of inferring this is a good place for there new home without regard for the size of the territory size we usually see Osprey require. Robert Loflin has a Ph.D. in Biology; he is the Natural Resource Director for The City of Sanibel. He states, “Osprey got use to less territory due to perfect conditions for feeding on Sanibel.” With 320 to 400 Ospreys in 44 square miles of the adjoining Islands of Sanibel and Captiva these barrier islands must just have the densest population of Osprey in the world.
Their well-being indicates the well being of the fish in one of the most important fish estuaries in the world.Ospreys are classified as hawks and Sea Hawk is another name by which they have been known since they feed almost exclusively on fish. However, Osprey differ from eagles, hawks, kites, and falcons in certain parts internally and “its long, strong claws, curved about one third of a circle, and completely round (not concave and grooved beneath), in equal length of its toes (not unequal as in other raptors) and in the heavy, peculiar scaled (reticulated) tarsus (shank) and short, dense feathering of the thighs…The lower surface, or pads, of the toes are covered with spicules, which help hold slippery fish; also, it is the only hawk that has outer toe reversible as in owls; this enables it to grasp its prey with two toes in front , two in back. Osprey have strong hooked talons and beaks…their feathers are also very oily for extra waterproofing as they plunge into the water. A mixed blessing since this makes them buoyant, so they can not go deeper than about three feet below the surface.”
The huge density of population on Sanibel is directly related to the fact that its estuaries, bayous and the adjoining Pine Island Sound are at most three feet deep putting all the fish in hundreds of square miles within their diving ability. After catching fish the Osprey first emerges and shakes off excess water in its feathering and then aligns the fish facing headfirst for more streamline flying which decreases the drag of the fish as they fly. Adult ospreys are 21 to 25 inches long and weigh 4 to 5 pounds. Males are usually a little smaller than females. When Osprey chicks fledge they are the same size as adults, but their chocalate-brown upperpart feathers have white tips, as if they were dipped in marsh mellow crème. Also, their eyes are orange, whereas an adult’s eyes are yellow.”