Ospreys are amazing raptors, bold and fierce with their piercing eyes, powerful talons, and broad wings. Those same features that make these birds so distinctive also make them exceptional fishermen—and that’s a good thing, as Ospreys are piscivorous and must continually hone their fishing skills for each meal.
The Fish That Ospreys Eat
Unlike most raptors that hunt a variety of prey—from insects to mammals to reptiles to even other birds—Ospreys hunt only fish. In fact, fish make up more than 99 percent of an Osprey’s diet, and they will only hunt other animals if there are no fish to be had. Ospreys have been recorded as preying on more than 80 different species of fish, and they’re often called fish hawks due to their exceptional fishing abilities. They will fish in both freshwater and saltwater and may take all different types of fish, including:
Despite the great variety of fish that Ospreys will hunt around the world, a single Osprey usually only hunts the two to three types of fish that are most prevalent in its favorite hunting grounds. Which fish an Osprey hunts depends on the habitat and water quality, the fish species that are most abundant, and the potential competition for certain types of fish.
Why Ospreys Are Such Amazing Fishermen
These raptors have a wide range of adaptations that help them with their fishing. By recognizing their different adaptations, birders can better appreciate Ospreys’ fishing prowess.
Ospreys have longer-than-usual wings, which give them more powerful lifting capability. This allows Ospreys to lift a heavy load of fish up from being partially submerged in the water. Depending on the fish an Osprey catches, its prey could equal 10-50 percent of the bird’s own mass, and longer, more powerful wings are essential to lift that meal into the air and back to the nest.
While all birds have talons and most curve slightly, Ospreys have very strongly curved, powerful talons. This gives them better piercing capabilities to puncture the thick scales and skin of their aquatic prey, and their talons can more easily hook into a fish’s body so it can be pulled from the water and carried through the air.
Ospreys have unique, barbed pads called spicules on the bottom of their toes. These spicules can more easily grip slippery surfaces, such as the wet and squirmy bodies of the fish they catch. This extra gripping power is also useful when Ospreys land on wet or slippery surfaces, such as logs or boulders that may be covered with wet moss or algae.
What do Ospreys and owls have in common? One of their rear outer toes is reversible and can be pivoted either forwards or backward. This allows Ospreys to manipulate and maneuver fish more easily, and after they’ve caught a slippery snack, they point the fish head-forward for better aerodynamics in flight.
Despite their large size, Ospreys can briefly hover. This allows them to pinpoint where fish may be schooling and set themselves up for an effective hunting dive, plunging feet-first into the water to catch their next meal.
While all birds have great eyesight, Ospreys have even better eagle eyes than some eagles. These birds can see through glare on the surface of the water, which allows them to find fish more easily so they can hunt in different light conditions.
When an Osprey dives into the water, a third eyelid—called a nictitating membrane—closes immediately to protect the bird’s eyes. This semi-transparent membrane is a pale, icy-blue color and allows some areas of light and dark to be seen even underwater.
If you’ve ever gotten water up your nose, you know how uncomfortable and irritating it can be for sensitive membranes. Ospreys don’t have this problem, however, because they have special valves that close their nostrils when they are underwater, protecting them from accidentally ingesting water.
Ospreys have dense plumage and a very active uropygial gland—or preen gland—that produces plenty of oil for waterproofing their feathers. This provides excellent insulation so the birds do not become waterlogged or chilled, no matter the water temperature.
With all these adaptations, it’s no surprise that the Osprey is one of the world’s best fishermen, and it’s always a treat for a birder to see them dive, plunge, and pull back out of the water with their next meal.