Osprey: the Fish Hawks Return (April 2025)
by Sairah Malkin
With spring now in full bloom, one of spring's most charismatic harbingers of the season has returned to its breeding grounds here on the Chesapeake – the Osprey (Pandion haliaetus)!
Ospreys truly are fascinating and beloved, with legions of dedicated fans around the world who have tracked their migration for years and share information about how to build nesting platforms. These birds have had more than one comprehensive memoir written singularly about them. John Audubon, the painter and ornithologist for whom the society of ornithologists is named, was an admirer of these birds and their fishing prowess, painting a spectacular Osprey in flight clutching a fish. These raptors are highly adaptable and have an almost cosmopolitan distribution, absent only from Antarctica.
Remarkably, their highest density on Earth occurs in the Chesapeake Bay area. If you’re reading this from the Chesapeake’s Eastern Shore, this may not surprise you: the Chesapeake hosts an estimated 30% of the world’s Osprey population. These magnificent and long-lived birds (surviving 25+ years in the wild) announce their presence dramatically upon return, building enormous stick nests, which they reclaim year after year, and generally creating a riotous noise when defending them or their young. Unlike other birds that form large colonies, Ospreys maintain territorial spacing, fighting with other birds for prized real estate.
So why is the Chesapeake so well suited to support huge numbers of Ospreys? There are likely several interacting factors. First, Ospreys are fishing specialists – unique among raptors, they consume an almost exclusively fish diet, which the Chesapeake provides in abundance. They are superbly adapted to this lifestyle with several notable features: long legs mostly bare of feathers to reach deep into water; large sharp talons and feet ornamented with rough spines for securing slippery fish prey; and a unique reversible outer toe that can swing backward that helps secure fish while in flight. The etymology of their Latin name, Pandion haliaetus, reflects this connection to fish, deriving from Pandion, a mythical king of Athens whose daughters were transformed into birds, combined with the Greek words halos (sea) and aetos (eagle). If you are what you eat, these birds are indeed ‘fish hawks’.
Second, strategies to eliminate key environmental toxins that proliferated after World War II have been highly effective. The impacts of some of these chemicals on raptors are well known -- most famously, the devastating impacts of DDT on eggshells and the resulting reproductive failures. From the 1950s until at least the 1970s, when DDT was banned in North America, Osprey populations were in sharp decline and listed as endangered in both the USA and Canada. Although Chesapeake populations suffered less than elsewhere, the elimination of DDT and similar pesticides in 1972 is recognized as one of the primary factors contributing to their remarkable resurgence across the continent.
A third reason for Ospreys' abundance in the Chesapeake Bay lies in their exceptional ability to live alongside human activity and our evolving approach to coexistence. While Ospreys naturally nest in trees, the decline of forests near suitable fishing waters has limited their natural nesting options. By the late 1970s, the Coast Guard shifted to more Osprey-friendly policies, abandoning their previous practice of preventing or removing nests from navigational aids. In addition, local residents began erecting dedicated nest platform structures throughout the region. Surveys conducted in 1973 and the mid-1990s document this transition: in the 1970s, about 1 in 5 Osprey nests were built on navigation structures, growing to about half by the 1990s. The 1990s survey found that over 90% of Chesapeake Ospreys were nesting on artificial structures—a testament to both conservation efforts and the remarkable adaptability of these birds.
Today, thanks in no small measure to local residents who continue to erect nesting platforms throughout the Bay and beyond, Ospreys have become both a remarkable conservation success story and a welcome symbol that the spring season has arrived.
References:
Henny, C. J., Grove, R. A., Kaiser, J. L., & Johnson, B. L. (2010). North American Osprey Populations and Contaminants: Historic and Contemporary Perspectives. Journal of Toxicology and Environmental Health, Part B, 13(7–8), 579–603. https://doi.org/10.1080/10937404.2010.538658
Poole, Alan R. 2019. Ospreys: The Revival of a Global Raptor. Johns Hopkins University Press. Baltimore, MD, USA
Watts, Bryan D.; Byrd, Mitchell A.; and Watts, Marian U. (2004) "Status and Distribution of Breeding Ospreys in the Chesapeake Bay: 1995-96," Journal of Raptor Research: Vol. 38 : Iss. 1 , Article 6. Available at: https://digitalcommons.usf.edu/jrr/vol38/iss1/6
More information about Osprey is also available here:
https://hawkwatch.org/raptor-id/raptor-id-fact-sheets/osprey/?gad_source=1&gclid=CjwKCAiAiaC-BhBEEiwAjY99qM2Xtu2xQQ7h-8ZGwwzaAR1AM1M-sUmifUGh0puuQ2nuaGuOFjgMrxoCF00QAvD_BwE
An Osprey tending her nest on a platform put up by Richie Long, adjacent the Horn Point Laboratory research pier. Original artwork by Julie Trommatter of Good Juju Designs.