Saving Seafood

Bald Eagle Recovery in Chesapeake Bay Raises Red Flags for Osprey

Saving Seafood

July 28, 2025 –  The Chesapeake Bay is once again teeming with bald eagles, a testament to decades of successful conservation efforts. A recent feature by the Maryland Department of Natural Resources (DNR), “A Soaring Success: Maryland’s Bald Eagle Population Recovery” by science writer Joe Zimmermann, highlights this remarkable comeback.

In 1977, a mere 44 breeding pairs of bald eagles were recorded in Maryland. Today, that figure has soared to over 1,400, according to estimates from the Maryland Bird Conservation Partnership. This dramatic rebound has established the Chesapeake Bay as a national stronghold for bald eagles, boasting the highest concentration of breeding pairs outside Alaska.

This recovery is largely attributed to sustained, science-driven policy. The 1972 federal ban on the pesticide DDT, which caused reproductive failure and eggshell thinning, was a pivotal moment. In Maryland, the 1984 Chesapeake Bay Protection Act further safeguarded critical habitat within 1,000 feet of tidal waters. These combined measures helped restore nesting conditions and bolster survival rates.

The scale and speed of this recovery have made bald eagles a symbol not just of national pride, but also of effective conservation action. “Bald eagles are a very good example of what happens when you find the solutions and take action, and now you can look at how they’ve come back,” said DNR conservation ecologist Dave Brinker.

Today, bald eagles nest in every Maryland county and in Baltimore City. The Bay supports not only year-round resident eagles but also seasonal visitors from both the North and South. “Through the year, we have three pretty unique populations of bald eagles,” Brinker explained. “There are local birds that are here all year long. Then southern breeding eagles disperse to the Chesapeake Bay to spend summer here because food resources are so good. And in the winter, northern populations that need a warmer place, they come down to the Chesapeake Bay.”

 

Bald Eagle Recovery and Its Interspecies Consequences

 

While the recovery of the bald eagle in North America, particularly along the Chesapeake Bay, is a significant conservation milestone, its resurgence raises questions about its impact on other piscivorous bird species that have also been rebounding from decades of decline. Chief among these is the osprey, a fish-eating raptor that shares habitat and prey with bald eagles throughout coastal and inland waters. The Chesapeake Bay, now home to one of the largest bald eagle populations in the continental United States, is also crucial osprey habitat, making it an ideal region for observing interactions between the two species.

In recent years, environmental organizations like the Chesapeake Bay Foundation and sportfishing advocates such as the Theodore Roosevelt Conservation Partnership have repeatedly claimed that industrial menhaden fishing is the primary driver of osprey reproductive failures in the Bay. Their public campaigns, regulatory letters, and media statements link declining nest success to a perceived, yet scientifically undocumented, drop in Atlantic menhaden availability—a key prey species for ospreys during chick-rearing season. Much of this advocacy draws on research by Dr. Bryan Watts of the Center for Conservation Biology at William & Mary, whose studies have indicated increased nest failure in parts of the lower Chesapeake. However, even Watts has cautioned against definitive conclusions. In a 2024 Associated Press article, he stated, “We do not know why menhaden have become less available to osprey,” and suggested climate change as a possible factor.

Beyond climate shifts, other ecological dynamics may be at play, but the menhaden-focused narrative has recently overshadowed attention to other potential pressures. Given the Maryland Department of Natural Resources’ announcement that the Bay now hosts one of the nation’s largest bald eagle populations, interspecies competition deserves closer scrutiny—particularly food competition stemming from kleptoparasitism, the well-documented behavior in which eagles steal fish from ospreys. These interactions, studied for decades by field biologists and ornithologists, warrant renewed attention in light of the bald eagle’s increasing population.

While the ecological relationships between bald eagles and ospreys are not yet fully understood, evidence from multiple regions suggests that competitive pressures—especially kleptoparasitism and nest harassment by eagles—may hinder osprey nesting success in areas with high eagle densities. It is possible that the recovery of one iconic raptor is, in part, coming at the expense of another. These dynamics deserve greater consideration from scientists, wildlife managers, and policymakers.

 

Top-Down Pressure: A 35-Year Body of Research Shows Bald Eagle Competition May Threaten Osprey Nesting Success

 

As bald eagle populations have steadily rebounded across North America, particularly in strongholds like the Chesapeake Bay, a longstanding body of scientific research suggests that their recovery may come at the expense of other raptors, especially ospreys. For more than three decades, field biologists and ornithologists have documented the effects of interspecific competition and kleptoparasitism, the act of stealing food, as a factor contributing to osprey nesting failures.

One of the most comprehensive analyses of these dynamics comes from a 2019 study published in the Journal of Animal Ecology titled “Top-down effects of repatriating bald eagles hinder jointly recovering competitors.” Led by Jennyffer Cruz and co-authored by Steve K. Windels, Wayne E. Thogmartin, Shawn M. Crimmins, Leland H. Grim, James H. Larson, and Benjamin Zuckerberg, the study evaluated 26 years of nesting data in Voyageurs National Park, Minnesota. The researchers found that as bald eagle numbers increased due to intensive protections, the populations of ospreys and great blue herons declined.

“Bald eagles are top predators and a flagship species of conservation that have benefited from intensive protection,” they wrote, “but this likely hindered the recovery of ospreys and herons.” The study documented that “eagle abundance was negatively associated with nest reuse (i.e., persistence) and success of ospreys,” and concluded: “The top-down effects of returning bald eagles were the main predictors of declining nesting demographics for ospreys and herons resulting in their failed recoveries.” Importantly, the authors found “little evidence of bottom-up limitations,” such as poor weather, habitat loss, or declining fish stocks, implicating competition and interference from eagles as a primary driver.

The literature documenting these dynamics stretches back decades.

In a 1994 field note published in The Journal of Raptor Research, Professors J. MacDonald and N.R. Seymour of St. Francis Xavier University in Nova Scotia documented a lethal encounter in which a bald eagle pursued and killed an adult male osprey that was carrying a white perch. A second eagle joined the chase, and after a brief pursuit, one eagle seized the osprey midair, dragged it to shore, and ate it. The authors believed the attack originated as an act of kleptoparasitism—food theft—a behavior they note is well documented between eagles and ospreys and which they described as “a common occurrence.” They also referenced a second lethal attack, described by Flemming and Bancroft in 1990, in which a bald eagle attacked an osprey nestling shortly after it had received a fish.

In 2013, four U.S. Army Corps of Engineers (USACE) staff members working at Lake Sonoma in Geyserville, California, documented what was believed to be the first officially recorded case of “cooperative kleptoparasitism” in which a pair of bald eagles worked together to steal a fish from an osprey. Their observations were formally published in 2014 in The Journal of Raptor Research and summarized in a March 20, 2014, article on Army.mil, which likened the coordinated and calculated nature of the predation to something out of Jurassic Park. “Rarely have humans seen them cooperating to hunt as a pair,” USACE ecologist Wade Eakle explained. “This was the first time we witnessed them actually cooperating to steal, from another species.” The two eagles forced the osprey to drop its trout, after which the larger female swiftly seized the fish and flew off. Rangers had been monitoring the nesting pair since 2001, but this behavior marked a milestone in understanding the extent of eagle dominance over other raptors.

Evidence for this behavior also includes a 1988 study by Dennis G. Jorde and G.R. Lingle, published in the Journal of Field Ornithology, which observed repeat patterns of interspecific kleptoparasitism along the Platte River in Nebraska. Their findings indicated that bald eagles not only routinely stole food from other raptors but developed learned strategies for doing so efficiently, particularly during important foraging periods.

Even outside peer-reviewed journals, naturalists and field reporters have provided consistent anecdotal corroboration. BirdWatching Magazine similarly observes: “Bald Eagles are known to steal fish from other birds, particularly Ospreys. They will aggressively chase Ospreys in flight until the Osprey drops its catch, which the eagle will then snatch midair or retrieve from the water.” Another article in the same publication added, “It is common for ospreys and eagles to be in the same hunting grounds. As the more aggressive raptors, eagles will often fight the Osprey and force it to let go of the captured prey. The eagle will typically swoop in to catch the stolen prey.” The Cornell Lab of Ornithology’s All About Birds guide echoes these observations: “A Bald Eagle will harass a hunting Osprey until the smaller raptor drops its prey in midair, where the eagle swoops it up”, a classic example of kleptoparasitism.

Collectively, these studies and field reports spanning decades point to a clear and well-established pattern: as eagle populations recover and concentrate in resource-rich areas like the Chesapeake Bay, their aggressive behavior and dominance in the food web may have measurable negative consequences for ospreys. The repeated harassment and food theft increase energetic costs for osprey parents, reduce feeding efficiency, and may contribute to nest failures.

While the recovery of the bald eagle in the Chesapeake Bay region is unquestionably a landmark conservation success story, it does not exist in ecological isolation. As concerns continue to emerge about osprey reproductive success in key habitats like the Bay, it is increasingly important to view this predator’s return within the broader dynamics of interspecies competition. Over the past 35 years, a robust and diverse body of scientific literature—supported by peer-reviewed studies, field notes, and firsthand accounts—has documented the kleptoparasitic behavior of bald eagles, particularly their tendency to steal fish from ospreys and, at times, directly harass or even kill them. This behavior, while natural, may contribute to the energetic costs and nest failures observed in osprey populations where eagle densities are high.

Even Benjamin Franklin, in an often-cited letter, criticized the selection of the bald eagle as the national bird due in part to its scavenging habits and its theft of fish from “the fishing hawk,” known today as osprey.

For my own part I wish the bald eagle had not been chosen as the representative of our country. … he watches the labour of the fishing hawk; and when that diligent bird has at length taken a fish, and is bearing it to his nest for the support of his mate and young ones, the bald eagle pursues him, and takes it from him.

While his concerns were framed with a satirical flourish, he anticipated a tension now supported by decades of ecological research. As wildlife managers and policymakers evaluate recent reports of declining osprey productivity, it is essential that they consider not only fishery-related factors but also the well-documented competitive interactions between these two raptor species.

 

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