The Osprey is a large member of the raptor family that feeds almost entirely on fish. They can be found around any body of water from lakes and reservoirs to rivers and ponds. Since the ban of DDT their numbers have increased and can be readily found in the London area once they return in early spring from their wintering grounds, which stretches from the southern United States to Central and South America. Ospreys are tolerant of human activity and several pairs nest within the city limits in parks, Environmentally Significant Areas and along the Thames River.
Ospreys construct their nests of sticks and line them with bark and grasses. The nest is placed in an open area where an easy approach can be made. Look for Osprey nests in tree tops, crotches between tree branches or manmade structures such as telephone poles and lights posts. Ospreys usually mate for life and will reuse the same nest from year to year adding material to it each year. Nests can be as large as 13 feet deep and 6 feet across. Clutch sizes are 1-4 eggs with incubation lasting 5 weeks. Both adults take care of the brood and fledging takes place after 8-10 weeks.
As with most raptors Ospreys have incredible vision and can spot fish underwater from heights of over 100 feet. Once a fish is spotted the Osprey briefly hovers overhead before diving feet first into the water. The Osprey is specially adapted for a fish diet with closable nostrils to keep water out, reversible outer toes and backwards facing scales on their talons to help hold onto fish.Most years Ospreys start to reappear in the London area in early April. Given the cold winter and increased amount of ice across their migration route it may be later this year, unless we experience a significant warm up. Keep an eye out along river banks and shorelines of lakes and ponds once the ice is off. Ospreys are sometimes confused with Bald Eagles but there are several things to look for when identifying them. Mature Bald Eagles are larger and much stockier than the rather slender Osprey and have a solid white head and tail. The body of a mature eagle is solid brown, with the Osprey being a mix of brown and white. Ospreys are the only large raptor with a solid white unmarked belly. Juvenile Bald Eagles are mottled on their undersides and lack a white head.
Keep an eye to the sky and in tree limbs overhanging bodies of water in your favourite birding area. If you see a large brown and white raptor there is a good chance you’ve just spotted an Osprey.