The males of dabbling duck such as mallard, teal, shoveler and pintail are brightly coloured, often with areas of iridescent plumage, but their females are relatively drab birds in feathers of mottled and spotted brown. This characteristic tends to be slightly less striking in the diving duck and even less so in the sea duck species but, nevertheless, it is not difficult to tell the sex of adult birds during the winter and spring.

One unusual but very important feature of the natural history of wildfowl is the manner in which they moult their plumage. Most other families of birds undergo a gradual moult during which the flight feathers are shed and replaced gradually over a protracted period. Wildfowl, on the other hand, moult all of their wing feathers simultaneously with the result that they become flightless for several weeks. The susceptibility of some male duck to predation during this flightless period is reduced by the fact that they typically moult out of their distinctive breeding colours and assume a drab appearance similar to the females and juveniles of their species. Other wildfowl, which do not exhibit markedly different eclipse plumage, may undertake moult migrations so that they spend the flightless weeks in places of comparative sanctuary.

The feathering of wildfowl has other important characteristics which particularly suit the birds to their aquatic lifestyles. As a protection against the inhospitable environment which they frequent, duck and geese have evolved a covering of heat-retaining down beneath an outer coat of closely interlocking feathers. A gland at the base of the bird's tail secretes waterproofing oil and frequent preening serves both to distribute this oil throughout the plumage and to maintain the interlock of the feathers. Additional protection against heat loss is provided by a subcutaneous layer of fat which, in healthy wildfowl, is considerably thicker than that possessed by many other families of birds.

Feeding Habits

Each species of duck or goose is also well adapted to its particular feeding habits. Dabbling duck are broad-billed and sieve water or mud to extract the small crustaceans or vegetable particles which form the staple part of their diet while geese and wigeon, being grazing birds, have shorter, more pointed bills. Those wildfowl which feed on land have strong, centrally placed legs well suited to walking whereas the diving duck are efficient swimmers by virtue of shorter legs situated farther towards the rear of their bodies.

In addition to physical differences, wildfowl have also evolved behaviour patterns which reflect their feeding requirements. Many species, especially in winter, engage in flock feeding and some, such as the shoveler, appear to unconsciously co-operate by feeding in long lines so that one bird can sieve the water which has been disturbed by the feet of the duck in front.

Breeding

In their breeding habits wildfowl also demonstrate a considerable degree of adaptation to their environment. Most duck species nest at ground level and, in consequence, they can suffer fairly high losses as a result of predation or flooding. Sitting duck may fall prey to foxes or feral mink while gulls and skuas are a threat to eggs and young ducklings. The survival of the species in such adverse conditions is assisted by the fact that duck lay fairly large clutches of eggs and the ducklings are able to walk and swim within a few hours of hatching.

Geese, being larger birds, are less susceptible to predation and tend to have a smaller brood size than most duck species. Both parents normally share in the protection of eggs and goslings. Young duck and geese grow at a rapid rate and those which breed in Arctic areas have to be fully fledged and ready to undertake an arduous migration by the end of the short northern summer. The timing of the breeding cycle is extremely important and there is evidence to suggest that day-length is the critical factor which stimulates behaviour so as to ensure that chicks hatch at a time of greatest food availability. This may be one of the reasons why wildfowl collectors in temperate countries have difficulty in breeding some of the species which spend the summer in the high Arctic. It is possible that day-length in Britain never reaches the threshold level necessary to induce breeding behaviour in those birds.

Migration

Many behavioural features will be observed and noted by the observant wildfowler but, above all else, he will be fascinated by the annual cycle of migration which becomes as significant to him as it is to the fowl themselves. Each year in April fowlers watch with a little sadness as skeins of geese pass high over the hills on their journey to more northern climes and then, come mid-September, we will thrill to the music of pinkfeet as they return from their breeding grounds once again. In October the pinks are joined by their larger greylag cousins while, in other parts of the country, similar migrations will be ending as whitefronts splash down at Slimbridge and the ever-increasing army of brent geese make their landfall in south-east England.

Pinkfooted geese migrating from Iceland to Scotland cover the distance of over 800 miles in a single day but, at the other end of the scale, duck such as wigeon, teal or pintail may have to travel almost 2000 miles from their breeding territory in central USSR and are likely to complete the journey in stages spread over a period of several weeks.

The precise mechanism by which migration is guided is not yet completely understood and it may differ considerably between different species of migratory birds. The swallows and martins, for example, appear to have highly developed directional instincts and birds in their first year will successfully find their way to their wintering grounds without the benefit of previous experience or adult company. In contrast, it appears probable that memory and experiential learning are of considerably greater importance to the migrations of duck and geese. Although there may be a degree of instinctive behaviour involved in the timing of migrations and in navigating over ocean areas, wildfowl seem to be able to alter their patterns of movement to take account of environmental changes and will return to places where food has been plentiful in former years whilst forsaking previously favoured areas which have become inhospitable. Geese especially tend to travel in family groups, the oldest members of which will have experienced several annual migration cycles.

In addition to the principal autumn and spring migrations, which are a fairly commonplace phenomenon in the avian world, some wildfowl species engage in pseudo-migrations. As previously mentioned, certain duck undertake a moult migration to places of relative safety prior to shedding their flight feathers. One German inland lake is regularly visited by a flock of over 10,000 pochard and up to 250,000 sea duck moult in the shallow seas around Denmark. Another mass movement of duck can be triggered by the sudden onset of particularly hard weather in winter. If, for instance, a severe freeze-up grips northern Germany and the Netherlands, we may witness a migration of mallard, wigeon and teal from those countries to eastern Britain.

When a wildfowler steps out on to the remote saltings he enters the world of the wildfowl and, if he is to be successful in his hunting, he must understand and appreciate the ways of his quarry. Each fowling expedition is an adventure - an adventure within which the discharging of his gun might be an infrequent occurrence. To the true wildfowler the failure to fire a shot does not detract from the enjoyment of his sport because he has spent time in the wilderness of a dawning estuary, he has been enthralled by the sight and sound of the fowl and he has learned a little more about the habits of the wild birds which feature so large in his daytime thoughts and in his night-time dreams.