For many people the Mallard (Anas platyrhynchos) is the best known duck in SE16. Partly because they are so numerous, partly because they are so noisy and also because the male (or drake) has such a showy plumage: the glossy green head, white collar, purple-tinged brown breast, black rump with white borders and a curled centre tail feather, grey-brown wings with iridescent blue speculum feathers showing when extended and of course the yellowish-orange bill tipped with black. The female (or more formally hen) is relatively dull in comparison being mostly a mottled buff to dark brown with buff cheeks, eyebrow, throat and neck with a darker crown and eye-stripe. Her bill is orange-black but she shares the same blue speculum feathers under the wing with the drake. The final distinction between the Mallard sexes is that the classic quack that we all associate with ducks is the vocalisation of female Mallard only; the males use a a nasal call and a high-pitched whistle.
The Mallard is unusual in being able to interbreed with other species of duck and produce fertile offspring. This seems to be the result of rapid recent evolution and leads to unusually marked adults being part of the Mallard social system. As the female Mallard is quite similar to the females of some other duck species, this can lead to some confusion in identification. Another factor in identifying Mallard is their period of moulting which leaves the summer plumage (or eclipse plumage) looking significantly bedraggled and unimpressive. During this period, Mallard are generally less visible and quite secretive.
We often see Mallard upended dabbling for their food with their rump in the air. This preferred means of feeding – rather than diving as some other species of duck do regularly – makes it easiest for Mallard to settle where the water depth is about 1 metre; whilst not sea-birds, Mallard are able to feed and breed on both fresh water – such as Canada Water, Southwark Park lake and Albion Channel – and brackish water – such as Surrey Water and Greenland Dock. Whilst they are omnivorous, during the breeding season their diet moves more toward insect larvae and other invertebrates supplemented by plant matter; at other times of the year, it can swing back depending on food source availability.
The breeding patterns in Mallard colonies are the subject of current scientific study. They form pairs in the autumn (October-November) and as with many duck species, they mate with the drake balanced on the back of the female. The drake has an unusual corkscrew penis which turns counter-clockwise; the female has equally unusual vaginal structures such as dead-end sacs and clockwise coils. These make it much more difficult for the drake to force himself on the female and achieve a successful fertilisation of her eggs. Once fertilised by her mate, the couple remain together only until the clutch is laid. The female will seek out a nesting location that is concealed, not too close to other nests and inaccessible to foxes; sometimes nesting sites can prove quite distant from water and sometimes unusual. A couple of years ago, a Mallard nested in one of the Mayflower’s window boxes in full sight of their customers! She will often seek to conceal the nest by pulling together the surrounding vegetation but will seldom collect plant material from any distance away. In early Spring, she lines the nest with a few feathers from her own breast and lays about a dozen eggs with a day or two between each. This totals more than half her body weight in eggs laid over only a fortnight; its a very stressful time for Mallard mums!
Once the clutch is laid, the drake’s role as protector is over and the pairing finishes. The Mallard mum stays on the nest for 27-28 days until the eggs start to hatch; they all hatch together over about 24 hours. The ducklings are already well-developed, able to swim and immediately imprint on their mum so as to remain warm and safe in her care as well as to learn how and where to forage for food. For the first month, the duckling’s down is yellow on the underside and face (with streaks by the eyes) and black on the backside (with some yellow spots) all the way to the top and back of the head. Its legs and bill are also black. The down is not naturally waterproof so they get theirs from mum. It takes 50-60 days for the newly hatched ducklings to become independent enough to fly so they are dependent on their mum for food, warmth and guidance for nearly two months. Mum also protects the brood from predators especially hawks and foxes as well as other Mallard who will kill small strong young if mum is absent.
The drakes are often still able to father a brood of ducklings when the pairings finish. There are also unsuccessful drakes who failed to obtain a pairing and these often form single-sex groups in the Spring. They will seek out females who may have had an unsuccessful nesting or who are for one reason or another alone and will chase the female for sex. When one of these female ducks is caught, the ensuing ‘gang rape‘ can be quite distressing for human onlookers! Drakes (and females once they have finished caring for their youngsters) begin to lose their mating plumage at the end of the breeding season and shed their flight feathers entirely. This means they are flightless for 3-4 weeks. This time is spent being as inconspicuous as possible as they are much more vulnerable than at other times of the year.
So this year when you hear loud quacking coming from the water’s edge, you will know it will be the female Mallards. When you see the males in their gaudy breeding plumage, you’ll be able to give them their proper name. And if you see a bundle of yellow fluff, you can look out for a concerned Mallard mum on her way to bring the wonderer back into her care. Enjoy the Mallard in SE16!