I’m watching from behind a wooden viewing shelter, taking refuge from the ferocious wind ripping across the flatlands of Wheldrake Ings. Even with a telephoto lens, it’s hard to get any decent images at such a distance on this grey morning in late winter, but my camera does manage to record a sequence of grainy photos, which show how the marsh harrier’s deadly attack unfolds.

The raptor lifts off vertically from the reeds, and I can see a waterbird – possibly a moorhen - hanging limply beneath its talons. Grasping its prey tightly by the neck, the harrier transports it through the air for a few metres before plunging down into another part of the reedbed, where it disappears from view to eat it.

The whole episode is over in a few seconds with remarkably little fuss. Birds of prey often cause a commotion when they appear in places like this - spooking clouds of ducks and waders into a frenzied, whirling panic flight – but that isn’t happening here: my photos show wigeon, apparently unconcerned, carrying on dabbling in the water close by.

It may not be as spectacular as a peregrine’s aerial assault, but it’s a salutary demonstration of the marsh harrier’s overwhelming, lethal power.

Marsh harriers were traditionally summer migrants to the UK, arriving here to breed in April, but increasing numbers are choosing, like this one, to spend the winter here. They’re attracted to the rich pickings on offer at places like Wheldrake Ings.

So, what is it about this place that makes it an internationally recognised site for wildlife? Its importance for nature all flows from the River Derwent, which today is meandering placidly a few metres to my right as I walk along the muddy footpath through the reserve.

Every winter, when the Derwent is swollen by rain, it bursts its banks, washes over the footpath and pours onto the surrounding farm meadows. Because the land in this part of the Vale of York is so flat, the floodwater forms large, shallow lakes.

As the floods recede in the coming weeks, the fertile silt they leave behind will encourage a rich variety of wildflowers to bloom – but in these last days of winter it’s still a paradise for thousands of birds that thrive around water: golden plover and lapwings clustered round the impromptu lakes; the haunting cries of curlews drifting on the wind through the endlessly flat landscape.

Flocks of geese roll across the distant skyline like clouds. Swans sail gracefully across the water, then spoil the serene image by taking off in a frenzy of splashes and noisy wing beats. Grey herons fly overhead with legs tucked in and necks stretched out.

In Swantail Hide – at the end of the footpath, surrounded by a tall reedbed – I settle down with my binoculars and watch distant ducks dabbling and upending in the shallow water. Dotted among the commoner mallard, shoveler and gadwall, I spot a handful of pintail – the males resplendent with their chocolate-brown heads and long, tapering tails.

There’s deeper water here too – pools better suited to ducks that find their food by diving, and Pool Hide gives me the chance to get close enough to photograph some of my favourites.

Take a strikingly contrasting black and white body, pair it with an iridescent, dark green head, then dab a big, round dollop of white just below the bright yellow eye. The beautiful, but slightly ridiculous, result is a male goldeneye.

To add to the comic effect, these dandies perform a courtship dance that involves flinging their heads right back and pointing their bills straight up at the sky. February is the right time of year for one of these extraordinary performances – but sadly the males I’m watching are more interested in diving for food than trying to attract a mate.

I walk back to the car park in the fading light, past a group of teal nibbling the wet grass. As I’m approaching the viewing screen where I saw the marsh harrier attack this morning, I accidentally startle a flock of wigeon. They take off in a great splashing, flapping mass, then circle round a couple of times before dropping down onto the water.

In a few weeks, most of the ducks will have moved on. As the meadows dry out, skylarks and other farmland birds will come here to nest. Brown hares will box in spring sunshine. Brilliantly-coloured dragonflies will patrol the riverbanks.

They’re all drawn to a special landscape that’s shaped by the changing of the seasons – and the ebb and flow of the river.