The bulk of our diving ducks are winter visitors, with Pochard (Aythya ferina, wingspan 78cm) and Tufted Ducks (Aythya fuligula, wingspan 70cm) making up by far the majority. Pochards breed in fair numbers in lowland Britain though in nothing like the quantity seen in central and eastern Europe. Most of the many thousands which winter here are males. The females mostly go much further south, though one turned up at a pond in Surrey three winters running in the mid-1990s, suggesting the species may be loyal to particular sites.
Tufted Ducks are among the most appealing of the duck family thanks to smashing plumage and perky behaviour - their quick, arcing dive a delight. They have increased in numbers in the last half-century, thanks largely to the unwelcome spread of the non-native Zebra mussel (Dreissena polymorpha). Breeding pairs are greatest in Scandinavia and Russia (perhaps a million) and it is some of these birds which swell the British population dramatically each winter.
The most controversial duck is the Ruddy Duck (Oxyura jamaicensis, wingspan 60cm), a North American native accidentally let loose into the wild here in the 1950s and now quite common with more than 500 breeding pairs.
Like so many invaders, they are more aggressive than the native species - males have been known to try and mate with female Pochards. Worse, a few have bred in Spain and cross-bred there with the related but rare White-headed Duck (Oxyura leucocephala), which is a larger species having a wingspan of 65cm. The pictured White-headed Duck is captive.
All Ruddy Ducks and hybrids are shot on sight in Spain and an attempt has been made to cull them here as well, with the plan to eradicate them by 2010. Backed by conservation organisations and financially by the European Commission, the cull presumably has a sound scientific basis.
So far it has not been a marked success, partly because of the amount of ground to be covered and partly because it has not been applied uniformly - you can still see free-flying birds on plenty of nature reserves.
However, the main inhibiting factor surely is that, like a number of drastic conservation practices, culling Ruddy Ducks is unpopular. Whether the people who oppose it feel the same about Mink, Terrapins, Mitten Crabs and American Signal Crayfish among others is debatable, but one doesn't expect consistency in such a matter.
Against that, it must be pointed out that the White-headed Duck would not be endangered in Europe in the first place were it not for excessive hunting of a species that is easy to shoot, along with the disappearance of many shallow, reed-filled wetlands due to drainage for agriculture.
The sawbill family of ducks consists of three species in Britain, the Goosander (Mergus merganser, wingspan 85cm), the Red-Breasted Merganser (Mergus serrator) and the Smew (Mergus albellus), all of which use their specially adapted toothed beaks to catch fish but none of which breeds in the south.
Despite not killing a significant number of Salmon or Trout, both Goosanders and Red-Breasted Mergansers are heavily persecuted in Scotland on that account, a typical example of allowing ignorant received opinion to replace calm scientific assessment. Happily, rather like the Coyote in North America, the more the Goosander in particular is persecuted, the better it seems to do.
Approximately 2,000 nest here, using holes in trees or in banks, and anything up to 10,000 come from colder parts of Europe to winter in Britain. I once saw 22 take off from the River Mole in Surrey.
Images © Jeremy Early. All rights reserved.
In 2013 I published My Side of the Fence - the Natural History of a Surrey Garden. Details may be found, and orders placed, via this hyperlink My Side of the Fence. In November 2015 Surrey Wildlife Trust published the atlas Soldierflies, their allies and Conopidae of Surrey, jointly written by David Baldock and me. Details are on this web page: Atlas.