With its eyes fixed on ripples in the water below, a patrolling osprey suddenly folds its wings. It plummets and, a split-second before contact, thrusts its legs forward. As British wildlife spectacles go, an osprey on the hunt is hard to beat, and July is a great month to see one in action.
When males, who do the majority of the fishing, have chicks to feed in midsummer, you can watch this drama at any time of day, though early in the morning and evening tend to be best. They patrol a variety of water bodies, from estuaries to rivers, reservoirs, fish farms and even small ponds. A hunting osprey circles or hovers over the water and then dives, typically from 10–40m. Success depends on many factors, most notably water clarity and the weather – calm, overcast days are ideal.
Adults usually make off with a fish after two or three dives, but juveniles rarely catch their own fish until they set off on their first migration. As a result most males do not leave their nest site until all the offspring have migrated.
So, what are the adaptations that make ospreys such master fishers? Tim Mackrill, from Leicestershire and Rutland Wildlife Trust’s Rutland Osprey Project, explains:
1 Super-keen eyesight
A high density of receptors in their eyes gives ospreys remarkable visual acuity, while a transparent ‘third eyelid’, or nictitating membrane, closes for protection when a bird hits the surface. Ospreys are also able to compensate for the refraction that makes fish appear to be in a slightly different position under the water.
2 Oily plumage
Ospreys have oily feathers to avoid getting waterlogged while grappling with fish (it can take several attempts to lift big prey). They spend a lot of time perched in order to preen – a gland on their rump produces the oil that they apply to their plumage.
3 Pale coloration
White underparts make an osprey’s silhouette less conspicuous to fish when seen against the bright sky. Juveniles look similar to adults from below, though the feathers on their upperparts have buff or whitish edging, so they appear lighter brown.
4 Long legs
The lanky legs of ospreys enable them to reach well below the water’s surface. The birds can seize fish swimming as deep as 1m.
5 Scaly feet and reversible toes
Ospreys have huge, scaly feet and razor-sharp claws that give a tight grip on wet fish. Small spines – ‘spicules’ – on the underside of the toe pads enhance their grip further. The birds’ outer toes are reversible, too, giving extra manoeuvrability when catching and holding onto fish.
4 places where you can see ospreys fishing
1 Rutland Osprey Project
2 Aviemore, The Cairngorms
3 Spey Bay, The Moray Firth
See ospreys fish in the mouth of the River Spey from the WDC Scottish Dolphin Centre www.wdcs.org/connect/wildlife_centre
4 Dyfi Estuary, Ceredigion
Watch the local pair fish amid stunning scenery. The nearby Cors Dyfi reserve hosts the Dyfi Osprey Project www.dyfiospreyproject.com