Ospreys (Pandion haliaetus) are some of the world’s best fishers. Once known as the ‘Fishing Hawk’ they are specialists at catching our fishy-friends from above at great speeds.
They are tawny-brown on top with a white underside. Males and females are very similar-looking, with females having a more darkened breast band. Both males and females sport the same ‘highwayman’s mask’ around the eyes.
With a wingspan of between 147-170cm and weight of up to 1.6kg they are a considerably large bird. Despite these physical characteristics they inhabit similar areas to eagles who, being larger and heavier, will often fight ospreys for their catch. There are documented cases of eagles attacking an osprey from above, forcing the osprey to drop its catch, then the eagle snags the fish in mid-air.
Ospreys perform shallow dives from 30-100 feet up, reaching speeds of up to 80mph by the time they reach the water.
With eyesight 3-5x better than ours they see the fish from high above, hover for a few seconds, then dive towards the water only switching to feet first at the last instant! Ospreys then crash into the water, making a splash and emerging with a fish hooked by their curved claws and assisted by gripping pads on their feet.
Their success rate of one in four attempts isn’t surprising, considering Ospreys have a reversible talon. So instead of a 3 in front, 1 at the back arrangement, they can have a 2-2 talon arrangement for extra grip!
Ospreys are able to carry their prey great distances and have the intelligence to orient the fish so it is facing head on to the wind for least air resistance.
Diet and habitat
Because their diet consists of 99% fish, Ospreys can be found near ponds, rivers, lakes, and coastal waterways around the world. Human habitat is sometimes an aid to the osprey. The birds happily build large nests on telephone poles, channel markers, and other such locations.
Artificial nesting platforms are common in areas where preservationists are working to re-establish the birds.
North American osprey populations became endangered in the 1950s due to chemical pollutants such as DDT, which thinned their eggshells and hampered reproduction. Ospreys have rebounded significantly in recent decades, though they remain scarce in some locales.
Most ospreys are migratory birds that lay eggs in the Northern hemisphere then fly south for the winter. Unlike other migratory birds they do not build large fat reserves for the flight, instead they hunt along the way.
Ospreys will typically lay 3 eggs during the Northern Hemisphere’s Summer, with the first eggs being laid in late April in a staggered fashion, with 2 day intervals between eggs. New breeding pairs will lay 2 eggs whereas older pairs occasionally lay 4.
Because their parents leave the nest and fly south for winter, juveniles must learn to fly before then.
After around a month confined to the nest they will start to lift off and hover above the nest for a few seconds known as ‘helicoptering,’ gradually gaining confidence and ability until they are capable of sustained flight.
For the first couple of weeks the juveniles will return to the nest for food before they start to hunt for themselves.
As the adults migrate the youngsters stay behind for the first 2 years until they are capable of the huge distances covered.
Although the IUCN Red List states the osprey is of ‘Least Concern’ and its population is increasing, ospreys are still threatened by a number of issues.
One big threat is the ever increasing use of renewable energy, specifically wind turbines, both inshore and offshore. They are unable to avoid the blades as they turn and often fly into them. Ospreys are also often caught-up in fishing nets and lines. Whether in-use or abandoned, fishing nets and lines are one of the major causes of oceanic wildlife termination.
They also suffer at the hand of the use of toxic fertilizers and pesticides on farms. These can run off into the rivers/lakes/sea and endanger the lives of the ospreys as well as its prey.
Thankfully ospreys are federally protected in the US and a federal permit must be obtained in order to take a nest. They are also listed on the Amber List of UK birds of conservation of concern and it is illegal to hunt them across most of the globe.
Article written by TerraMar’s Education Development Intern – Tom Carr