Photo: Osprey and Crow, Carol Stalun
William Young
Carol Stalun, who is a skilled and talented nature photographer, took photos of an Osprey killing a crow. This is probably the first incident, documented with photographs, of an Osprey killing a wild bird.
Carol Stalun
On Saturday, March 6, 2021, Stalun saw an Osprey along the Potomac River in Old Town Alexandria. Stalun was in the area where there is an Osprey nest from previous years on a platform on pilings in the river. She had seen a male Osprey in the same area the previous day (the first one she had seen in 2021), and she was checking to see if he was still there.
At 8:33 a.m., Stalun saw a male Osprey on a piling not far from the platform with the nest. At first, she thought the Osprey had a fish in his talons. When she looked more closely, she saw that the Osprey had a crow. Fish Crows were mobbing the Osprey, and Stalun assumed from the vocalizations of the other crows and the location on the river that the Osprey's victim was also a Fish Crow. After being harassed by the other crows, the Osprey flew off with the crow in his talons, did a circle, and returned to the piling. He continued to peck at the crow, who was still alive. The Osprey pecked at the crow a bit longer before flying with it to the platform with the nest, dunking the crow in the river along the way. At 8:45 a.m., the Osprey arrived at the nest and dropped the crow into it. Because the nest is deep, the crow was no longer visible after the Osprey dropped it. Stalun had not seen the Osprey initially grab the crow.
Carol Stalun
The incident is exceptionally unusual for many reasons.
According to the Cornell Lab of Ornithology's Birds of the World, almost every published account says that 99 percent of the diet of Ospreys consists of live fish, with a wide variety of fish species taken. Fish captured generally measure 25–35 centimeters (10-14 inches) and weigh 150–300 grams (5-10 ounces), although fish up to 2,000 grams (4.4 pounds) have been reported. According to The Sibley Guide to Birds (2nd edition), a Fish Crow weighs 280 grams (about 10 ounces), so it is in the normal weight range of fish Ospreys normally catch. A Fish Crow measures 38 centimeters (15 inches), so its body is only slightly above the size range of normal Osprey prey.
Ospreys are one of the most widely-distributed birds in the world. They are found on all continents except Antarctica. Unlike most bird species who conceal their nests, Ospreys build huge nests, usually in open areas. The nests are easy to monitor and study. Some nests are equipped with webcams so that researchers can see exactly what prey is being captured. There is believed to be no documented evidence of an Osprey bringing bird prey to its nest.
According to Birds of the World, there are anecdotal observations of Ospreys catching non-fish prey, including birds, snakes, voles, squirrels, muskrats, salamanders, mollusks, and even a small alligator. There is a documented report of an Osprey attacking a lure pigeon used by hawk banders at Cape May, New Jersey. A lure bird is placed in a small harness, and its flapping induces hawks or falcons to fly into a nearby net. The lures are captive birds who are not wild.
Birds of the World also mentions reports of Ospreys trimming their nests with the skeletal remains of birds, but this might not represent prey taken. For instance, remains of birds found in nests in Arabia were up to the size of a Socotra Cormorant (80 centimeters, or 31 inches) and Slender-billed Gull (37-42 centimeters, or 14.5-16.5 inches), but it is unclear how or if these species were caught by an Osprey. An Osprey expert with whom I communicated suggested that the dead crow might have been put into the nest for decoration rather than to be eaten. We do not know what happened to the crow after it was deposited in the nest. But Ospreys are not known to decorate their nests with either birds or feathers. Ospreys sometimes interweave plastic bags or other refuse into their nest. This might to be done more for structural rather than aesthetic reasons.
An Osprey usually will not bother other birds unless it feels threatened. I spent many hours shooting footage of an Osprey nest at the Belle Haven Marina in Alexandria for my videos Osprey Love Nest and Osprey Love Nest 2: Feeding and Fledging. The Belle Haven nest was on a piling in the river, near a boat ramp. The Ospreys at that nest were not bothered when ducks, geese, and grebes swam directly under the nest, and they never showed any interest in attacking these birds. The Ospreys also paid no notice to House Sparrows who built a nest among the sticks of the Osprey nest. Only large birds flying above the nest caused the Ospreys to become alarmed.
The crow was not scavenged, because it was clearly alive in some of Stalun's photos. Had it been injured and flapping around in the water, it is unlikely that the Osprey would go after it. Ospreys often see uninjured birds swimming and flapping in the water, and they normally leave them alone. I don't know if a certain type of thrashing in the water might trigger a different response than an uninjured bird swimming. I am unaware of any reports of this happening.
Crows do not often attack Ospreys. The corvid expert Dr. John Marzluff, from the University of Washington, sent me an article that he co-authored about the mobbing of Ospreys by American Crows. The article said that American Crows aggressively mob a variety of natural predators and learn to recognize unique threats. Because mobbing is a costly and risky behavior, Marzluff and the other authors hypothesized that crows would selectively ignore benign members of other species that look similar to predators, perhaps even learning to do so. Through a series of natural observations and experiments, they found that American Crows were more likely to mob Red-tailed Hawks and Bald Eagles than Ospreys. Mobbing intensity was higher toward a taxidermic mount of a Red-tailed Hawk than toward a mount of an Osprey, indicating that mobbing increases with the risk posed by the predator. However, the authors also found that Ospreys were more likely to be mobbed in locations where they rarely occur, suggesting that crow populations that frequently encounter Ospreys habituate to this benign raptor. For the incident that Stalun witnessed, the Osprey was in a location where it regularly occurs, and it is possible that the mobbing behavior by the Fish Crows began only after the Osprey had seized its victim.
An Osprey expert with whom I communicated suggested that the crow might have been trying to get at a fish the Osprey had caught. This is improbable, because had the Osprey been flying with the fish, the crow would not have been able to carry it, even had the Osprey let go of it. Also, it is unlikely that an Osprey with a fish (its normal food) would drop it and grab a crow (not its normal food).
The most likely explanation might be that a Fish Crow was harassing the Osprey and got a bit too close. Smaller birds tend to attack a larger bird in groups rather than as individuals because there is safety in numbers, and the larger bird will have more difficulty grabbing any one of them. Osprey's have very strong legs and feet, and if the one Stalun saw managed to grab the crow's back, the crow would not have had much of a chance to escape. When the Osprey took the crow to the piling, it pecked at it, perhaps to kill it and make it easier to carry. It is not known whether the Osprey ever ate the crow.
Photographs of the Osprey with the crow can be seen at Stalun's website . The 60 photographs show the encounter in chronological order, starting with the Osprey holding the crow on the first piling and ending with the Osprey dropping the crow into the nest. Stalun's photographic documentation of this event is an example of how citizen science can produce an important contribution to ornithological research.
William Young is a writer from Arlington, Virginia. His book The Fascination of Birds: From the Albatross to the Yellowthroat was published by Dover in 2014. He has taught numerous classes about birds for the Audubon Society of Northern Virginia. The nature videos he has created for his YouTube channel have had more than 650,000 views. Along with Ashley Bradford, he is the co-creator of the MPNature.com website, which contains a wealth of information about the natural history of Monticello Park in Alexandria, VA.