One of the compensations of the cold months in this country for anyone who enjoys the natural world is the great arrival from the north of wintering wildfowl, of wild ducks, wild swans, and above all, wild geese. Britain is a winter haven for hundreds of thousands of these waterbirds which breed in what the naturalist and writer Mark Cocker calls "the crown of the planet" – the halo of land around the Earth's northern latitudes, below the Arctic, from Canada, through Greenland, Iceland, Northern Scandinavia, Siberia, and back to Canada again.
In summer the empty tundra here is ideal for nesting and raising young, with little disturbance and few predators, but in the winter it is locked up tight in ice; wildfowl have to flee south to survive, to warmer regions such as the British Isles where there are ice-free estuaries and snow-free farmland.
Wild geese, especially, are notable visitors as they appear to be growing in numbers – bucking the trend of worldwide wildlife decline – and their autumn arrivals are becoming ever more dramatic. Last October as many as 40,000 barnacle geese arrived on the Scottish island of Islay, after a 2,000-mile flight from Greenland, and as a record 28,000 of them congregated in one place, the RSPB reserve at Loch Gruinart; more than 7,000 Greenland white-fronted geese reached Islay at the same time. But even these numbers are dwarfed by the dark clouds of pink-footed geese from Iceland which now fill the winter skies of north Norfolk; there may be as many as a quarter of a million of these hefty, dog-sized birds in total and their vast 20,000-strong yelping flocks provide one of Europe's greatest wildlife spectacles. If you can't get to Holkham, or The Wash, there are a number of videos on YouTube which will give you a vivid idea of just how astonishing this phenomenon has become.
Yet spectacle isn't everything. Last weekend I had a winter wildfowl encounter at the opposite end of the size and drama spectrum, which was memorable. The species in question was the teal, which is the smallest British duck – indeed, it is the smallest duck in Europe – and the location was the River Thames in London.
Teal have for centuries been a celebrated quarry of wildfowlers, because they fly so fast and shoot straight up off the water. (The collective noun for them is "a spring" of teal.) But unless you're a keen birder who goes out to lakes and estuaries, you won't often see them, even though we get about 200,000 wintering birds from the Baltic region. (Only a couple of thousand pairs are resident and breed here).
Teal are not your duckpond sort of duck and they're not really your urban river sort of duck either, but the part of the Thames where I saw them bids fair to be wild, even within London, and this is the stretch upstream of Kew Bridge, where the river flows between two great estates – the Royal Botanic Gardens on the eastern side, and Syon Park, home of the Dukes of Northumberland, on the west. Biking along the river between them, as I was, you could be deep in the countryside.
The river was dropping, exposing its gravel shoulders, and in a small bay I saw a diminutive grey duck with a chestnut head and a dark green eye patch. I realised at once it was a drake teal; he had his plain brown duck with him, and the pair of them were in the shallows at the water's edge, sifting the gravel in their beaks for invertebrates. Something about them I found enormously attractive. I think it was partly their subtle colours; partly the fact that they weren't very common; but I also realised, as I watched them feeding unconcerned, 50ft away, it was partly their very size.
Small things seem to carry within them some strange attraction of their own. We can see it in human artefacts: think of cottages; the Mini (the car); model villages; dolls' houses. And smallness seems to exude a similar magnetism for us in the natural world. Who wouldn't be fascinated by the bee hummingbird of Cuba, the smallest bird on the planet, smaller than a thumb? Yet the attraction of smallness is relative, not absolute.
For the bee hummingbird is the size of a largish beetle, and in a beetle, these dimensions would seem unremarkable; so it is clear that what charms us really is something which is a miniaturised version of something else – something which is generally familiar, but smaller than we expect.
Why this should be so I have no idea, but I certainly felt it with the teal, and I felt it more and more as in the next bay I saw another pair, then another, then another. Swimming next to mallards, as they occasionally were, they looked like tugs next to oil tankers – ducks for a smaller world.
All along the river there were teal feeding in the gravel at the water's edge, in what seemed to be very contented pairs, and by the time the gravel ran out, at Isleworth, I had counted 76 of them.
They'll be gone soon, off to Sweden or Lithuania or wherever for the summer. I felt privileged to have seen them in west London, even though it was a very un-wild-geese-like encounter, without a scrap of drama or spectacle, in fact, it was entirely everyday and humdrum, and devoid of anything to grip you, unless you are interested in the natural world; but if you are, you might have shared my view, biking home, that the pleasures of winter can be no less intense for being small.