Resident Bald Eagles & Migratory Osprey

Story by Capt. Mike Ostrander

Photos by Bill Draper

February 22, 2025 

Patterns emerge from watching resident bald eagles as they interact with migratory osprey. Over time behaviors become understandable and often predictable. Interactions between the two species begin upon first arrival of the osprey in late winter. By March 1, the first osprey returns and by mid to late Septebmer, the last osprey departs on its annul migration south. During these seven months there are no two species that have more to do with each other and are easier to observe than migratory osprey and resident bald eagles on the James River.

The following observations come from an area called Jefferson’s Reach, a seven mile section of the upper tidal James River, about fifteen miles downriver of downtown Richmond, Virginia. It’s a place I call home and have spent the last thirty years working and observing nature. Over the last sixteen years, observing the resident bald eagle population’s annual life cycle, includes numerous daily, seasonal interactions with migratory osprey.

Understanding their behaviors is magnified by knowing the individual birds, their nesting sites and territories. Resident bald eagles do not migrate, and are highly territorial. Osprey have incredible site fidelity, returning each year to the same nest site making individuals, and pairs, from both raptor species of Jefferson’s Reach recognizable. 

Resident eagles have defined boundaries, using specific trees along the shoreline, or man-made structures to help delineate their territories. Between each territory is a buffer zone, or a “no-fly zone”. In Jefferson’s Reach, these buffer zones are about five hundred feet wide and each territory is about half to three quarters of a mile long. The expanse of their range, beyond the shorelines, are known only to them. Each pair diligently protects their territory from all other eagles, and the closer an intruder wanders towards the nest site, the more intense the defense becomes.

Osprey are both territorial and communal. They are extremely protective of the nest and immediately around it. They become hyper-territorial when the eggs are laid, when the chicks hatch and near the time the young are about to fledge. During these times, their behavior changes and the intensity of protection magnifies, including their need to create a larger protective space around the nest. Osprey will chase any bird that flies even remotely near the nest, and even crossing the entire river. It will even assert its dominance over a vulture, who otherwise would have nothing to do with the osprey. Away from their nests, osprey can be communal, both in hunting for fish in shallow flats of the river, and helping each other out during times of need (more to come on this). 

An easy example of understanding osprey behavior is by learning to recognize it’s loudest, highest pitch. When you hear this high level shriek once, or multiple times, it means one thing; there is an eagle on the wing, approaching their space. It is a warning call to the eagle and other osprey in the area.

Osprey are a major food source for resident bald eagles. No, eagles don’t eat osprey and generally do not bother them unless an osprey has been successful at plucking a fish, from the river. With incredible eyesight, deadly accurate diving and grasping skills, osprey are one of natures greatest anglers and the fish they catch are a considerable food source for eagles. 

Nearly one hundred percent fish eaters, osprey appear tireless in their efforts while on the hunt remaining in the air for long periods of time. Osprey fly above the river, peering down, always looking at the river with specialized eyes, searching for movement, shape, color and other things we’ll never know. If a fish is located they hover, momentarily angelic, holding in place, flapping while considering a potential dive. If it decides the fish is worth pursuing, the osprey tucks its wings, dives head first, and just before reaching the water extends its two feet forward, crashing talons through the surface and towards the target with a mighty splash. Each foot has four toes with talons, three forward facing and the hallux in the back. Osprey have the unique ability to reverse the outer, front toe to the back, next to the hallux, temporarily creating a foot with two talons on top and two on bottom, the perfect tool for clenching and piercing fish. 

If osprey are successful at catching a fish, the eagles are the next to know. Bald eagles are opportunistic, patient and make a living stealing fish from osprey. This act of one animal stealing food from another is called kleptoparasitism. Resident eagles instinctively rely on this strategy to survive and the timing of the osprey’s arrival helps them keep food coming to the newly hatched eaglets.

Kleptoparasitism takes energy and a lot more energy than simply diving towards the water to scavenge a dead fish from the surface. Also called “pirating”, kleptoparasitism is introduced to the eagle chicks as soon as they can see over the nest. They watch as their parents attempt to steal fish from osprey. The adult eagles continue demonstrating this to their young over the course of the time they have with them. Eaglets fledge (leave the nest) at three months and leave its parent’s territory for good around six months. Once on their own, the juvenile eagles continue to learn from other eagles, develop their own skills, and by the time they become mature eagles, at five years old, they will have mastered the art of pirating. Instinctively, they too will educate their own young how to steal fish, and continue this cycle that has developed through time.

When viewing an encounter between the two raptors, you get an appreciation of the bald eagle’s massive size. Osprey are large birds, but the eagle is about a third larger. As the two draw close, with both bird’s wings fully extended, in that moment, you can see and appreciate the eagles advantage in size. 

Battles between osprey and eagles are frequent, and begin with an osprey hunting and a resident eagle perched alongside the river, patiently watching every movement in its territory. With keen eyes, an eagle immediately knows if an osprey’s dive was successful. If so, the eagle takes flight, gathers speed, as the head and neck drop and its rapid flapping wings begin to dig slightly, forward to back, to gain top velocity.

The eagle catches up and aligns itself to the osprey, following closely just behind and below. As if in a synchronized dance, the eagle matches each sharp turn and escape tactic of the osprey. At the right moment, the eagle rolls upside down, instantly turning one-hundred-eighty degrees, shooting its talons upward into the the osprey's lower section, focused on the talons and fish. The eagle may successfully grab the fish from the osprey’s talons and leave, or cause the osprey to drop the fish in mid air. If the fish drops, tumbling downward towards the river, and the action is high enough the eagle will turn, dive down, faster than the gravity speed of the fish, and snatch the fish out of the air with a smooth, fluid action, completing the perfect act of kleptoparasitism.  

Eagles are not always successful at stealing the fish. Sometimes, just before the eagle makes contact, the osprey will fake one direction and make a turn in the other direction, momentarily escaping, breaking the sequence of synchronized moves, and creating distance between the two. If the eagles momentum continues in the opposite direction of the osprey, it slows and either repositions itself back towards the osprey for another attack or gives up its efforts flying back to perch to watch for the next opportunity. Once in a while the result concludes with the fish dropping from the ospreys talons back into the river, to swim away and have one heck of a story to share. 

An interesting communal bond between osprey occurs when an eagle is flying towards an osprey with a fish. Often, another osprey from a different territory will fly to the rescue diving right in at the eagle, swooping and diverting it away, thwarting its pirating efforts. This communal bond between the osprey works well for them to maintain their catch, and while a common sight, is one of a few situations where an osprey will chase an eagle. 

Nearly all osprey nests are built within a resident eagle’s territory. A single eagle territory may have as many as four osprey nests. Given the amount of time these neighboring raptors spend with each other over seven months year after year, the they probably know each other well, honing in on each others moves, gaining insight into their strengths and weaknesses. 

The Photo's Stories

Top Right: Interactions between eagles and osprey are commonplace from March through September on the James River, and beyond. In this image, more than likely the osprey seems to be diving at the eagle. It could be one of two things. The bald eagle just harrased the osprey trying to take its fish and it was dropped. Neither bird keeping it and the osprey then will turn on the eagle after it has attempted to steal it's fish. Or, this is one of the circumstances when another osprey will come to the aid of anothe osprey with a fish (as written in the story). 

Top Left: A resident bald eagle approaches an osprey with a fish. This is closing in on the point the eagle will swoop upward, turn 180 degrees and attmept to steal the fish from the osprey. They use their large talons to grab it from the osprey. 

Bottom Left: This is a juvenile eagle turning 180 degrees moments before launching it's body and talons upwards into the underside of the osprey. This eagle could be considered a sub adult as it looks to be closer to four years of age. The head and tail filling quite full with white feathes. 

Bottom Right. A shad has been dropped by an osprey, and the adult bald eagle dives and catches up to it. After the dive, the eagle turned, making a quick manuever to right itself and aim towards the falling fish. This photo was taken a half a second from the talons reaching out to grab it out of the air, with a smooth, fluid motion.