An Osprey Evaluation
by Sergei Poljak

The osprey is a truly magnificent creature. Hailing from all continents (excluding Antarctica), this royal bird is quite the success story. This is partly due to its rank on the ecological food chain; it has no predators as an adult, and its life span ranges from 20 to 25 years. Likewise, its habitat is somewhat easy for humans to manipulate, allowing young fellows like me (and Peter Borgemeister, of course) to build thousands of nests across the country. Through the banning of DDT, and the steps of many youthful, dedicated, and righteous individuals, the osprey has regenerated its numbers to upwards of 500,000.

The osprey itself is a remarkable beast, and with adults reaching wingspans in upwards of 6 ft., the bird is virtually exempt as prey (well, not counting humans). Its weight is impressive, at only 3-5 lbs., especially considering its height of about 2 feet. The body is generally white, with brown encompassing the feathers of the wings, and with females and occasionally males, a facemask around the eyes. The talons are typically brown or black, and are astonishingly large, allowing the bird to snag fish up to 14 inches in length. The osprey was one of the animals originally observed by the great Carolus Linnaeus in the 19th century; it has since been given its own family, Pandionidae, of the Aves class. There are four subspecies in various regions of the world. The osprey is also considered a raptor, which is any bird that preys on other animals.

As stated previously, the main source osprey nutrition is fish. In fact, 99% of osprey meals are fish: however, in rare cases, they will consume small rodents and reptiles. The fish consumed are generally 5 - 10 oz., but larger prey can be extracted (up to 68 oz.). The bird is extremely well adapted to the seizing of its prey, with its reversible outer toes and barbs lining its talons. Additionally, backwards facing nostrils help keep out water during steep dives. In accordance to its diet, the osprey resides in environments where fish are readily available. Most notably, they are found in estuaries along coastal waters, but are also plentiful in lakes that may be more inland. The osprey's natural habitat would also consist of a dead or otherwise open tree near the water; however, as more and more development occurs, they have taken up residence on telephone poles, rooftops, and of course, our beloved osprey platforms. Because of this relative lack of habitat specificity, the osprey has been particularly successful in adjusting to a more urban environment. The adult bird is relatively exempt from predators, but the eggs are not. Rodents and other large birds will eat many eggs, and occasionally juveniles, when a parent is not able to keep watch. Other hazards include high winds, which can topple nests, and human chemicals, such as DDT, which we will discuss later.

The offspring reproduces in the fashion of most birds, which is to say it lays approximately 2-4 eggs per year that may or may not survive to hatch. One of the most important aspects of the osprey breeding process is the habitat. The birds must be near coastal waters and they must be able to find a suitable area to build a nest. If these conditions are not met, breeding can be delayed. Some birds don't breed at all until they are 5-7 years old, but most breed by the age of 4. Furthermore, the nests must be efficient in the conservation of heat, as to allow the eggs to incubate for a full 5 weeks before hatching. The eggs are usually laid within a month of settlement, and eggs hatch a month later. This results in most juveniles being birthed by the end of June, depending on the nest location, and whether a nest is already built, needs renovation, or needs to be completely constructed from scratch. Around Long Island Sound, the osprey arrive at the end of March, and eggs are hatched by mid June. The average number of chicks born is usually around 2-3, but occasionally there can be 4-5 chicks in a nest. These latter cases almost always result in at least on of the chicks starving, as the parents (father) can only hunt for so many mouths. Most nests will produce 1-2 fledgling per year that will grow into an adult, but only 40% of these will in turn survive the journey south. The others cannot survive, mostly because of a lack of food. If resources are particularly scarce, the oldest hatchling will receive the better treatment. Osprey are also miraculous birds in that they are generally monogamous for life, reuniting with the same mate year after year. However, like humans, there are intermittent cases of adultery.

Osprey are generally migratory birds (albeit some species from Australia), and routinely travel between continents. In the Americas, many birds from the northern hemisphere can be spotted in the southern hemisphere during the winter. Birds from Connecticut are mostly spotted in Florida, Central America, and northern South America above the equator. They return around the end of March, and are on their way out by late September or early October.

The osprey suffered a very large hit to their population in the 50s and 60s, mostly due to the emergence of DDT in the environment. At first it was used as an insecticide, but it quickly spread through the food chains. Biomagnification can be blamed for this; each small fish the osprey consumed had a small amount of DDT. Eventually, the concentrations rose high enough to affect the calcium metabolism in the birds, causing them to lay thin- shelled eggs that were prone to rupture. Even after the breakthrough novel Silent Spring by Rachel Carson (1963), DDT wasn't banned in its entirety in the U.S. until 1972. It was around this time that the osprey began to make a comeback and, with some help from our platforms, they are thriving.

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