Waterfowl are widely known by birders throughout the world. These aquatic grazers and foragers are herbivorous, plant eating birds. They tend to be large sized, long-necked and long-legged birds and all have large bodies.
The habitats in which these birds are found are mainly inland, ranging from large lakes to small ponds but including rivers, estuaries and some coastal regions. Many favour large, reasonably open areas and are also readily seen on grassland surrounding the water bodies. Some are a little more secretive and like the cover afforded by reed beds and marshes.
Feeding techniques include grazing in water or on surrounding land as well as dabbling and diving for plant materials below the water surface.
Various factors such as their large size and general appearance coupled with the presence of spurs on the wings of some species suggest that some species are amongst the most primitive of our modern birds. Their limited distribution, in specific regions of the world, is consistent with evolution in Gondwanaland about 90 mya.
I have photographs of many of the birds in this group but have limited myself to a few examples of birds which are of special interest to me for the purpose of this review.
Screamers and Magpie Goose.
Screamers, in family Anhimidae, are only found in South America. The Southern Screamer (top, right) eats grasses and crops on land close to water as well as aquatic vegetation in the water.
The Magpie Goose, photographed at Hastie's Swamp, near Cairns (left) is only found in Australia and New Guinea. It may be the link between the Screamers and Geese and Ducks. It eats grasses and rushes.
Whistling Ducks.
Whistling Ducks may be the link between the Magpie Goose and the Geese. They have become established in the tropical parts of Australasia, Africa and the Americas where they favour marshy and swampy inland water bodies. In Texas the Black-bellied Whistling-Duck is present all the year round and has become common around habitation. They eat plant materials, aquatic seeds and aquatic invertebrates. The White-faced Whistling Duck (right) is found in tropical regions of South America and Africa.
Shelducks.
Shelducks and Sheldgeese fly well and are found in Australia, Africa and Europe where they are equally at home on land or in water where they forage for insects, invertebrates, molluscs and crustaceans. They appear to be intermediate between geese and ducks.
The Common Shelduck (left)was photographed at Inner Marsh Farm, on the Wirral in the UK. The frontal shield is reminiscent of the Coots and Swamphens.
Swans.
Swans are large, confident birds which can fly well. They feed in the water eating aquatic vegetation and often up-end to take plant materials from under the water surface.
Swans have a sole species, of genus Coscoroba, which is the only all-white Swan in the Neotropics. This bird has strong affinities with Geese so it may be the evolutionary link between Geese and Swans. The Freckled Duck is a close relative of the Swans and may be the sole survivor of a primitive group of Waterfowl.
Swans have established geographic niches in specific regions of the world as follows:-
- N. America – Trumpeter Swan, Tundra or Whistling Swan.
- S. America – Coscoroba Swan, Black-necked Swan.
- Eurasia – Mute Swan, Whooper, Bewick’s.
- Australia – Black Swan. I photographed the Black Swan (right) at the Pugh Logoon, Sydney, Austrslia.
Geese.
Geese fly well and are found on all continents and many isolated islands. The Anser species are birds of the Northern hemisphere. The Branta species can be found closer to the tropics. They eat plant materials and aquatic invertebrates and are quite often seen grazing on land as well as in the water.
They have established niches which relate to their feeding techniques and breeding in various parts of the world:-
- Grassland grazers – Cape Barren (Australia), Swan Goose, Bean Goose (Europe), Canada Goose (N. America).
- Stubble grazers – Pink-footed (Europe), White-fronted Goose (America, Europe) Red-breasted and Greylag Goose (Europe).
- Grass root feeders – Snow, Ross, Emperor Goose (N. America).
- Coastal and estuary feeders – Barnacle, Brent (Europe).
- Volcanic slopes – Nene endemic to Hawaiian Islands.
- High altitude – Bar-headed Goose (Asia).
The Bar-headed Goose (left) is a high altitude species from Central Asia which sometimes appears in Europe. I photographed this one Pen-y-Ffrith, near Ruthin in the UK.
Ducks.
Ducks are mainly dabbling and diving feeders. Although plant materials are still their main source of food, the aquatic environment offers a wide range of other foods in various parts of the world which can be identified by their feeding technique and behaviour:-
• Mountain stream feeders – forage for aquatic animals, plants, small fish and snails which they find under rocks in fast flowing streams. The Blue Duck of New Zealand and the Torrent Duck of the South American Andes are usually found at altitudes of at least 1500m. Ornithologists appear to relate them to the Shelducks. The Torrent Duck (below) was photographed in Ecuador.
• Filter feeders – favour the shallow waters of inland pools and lakes which can be fresh or brackish. The Pink-eared Duck of Australia has affinities closer to Shelducks rather than Dabbling Ducks. Shovelers filter feed on nutritious surface materials.
• Perching Ducks – are small birds which perch in trees but otherwise behave like dabbling ducks. The Muscovy Duck favours tropical forest lakes and rivers in Central and South America. The Wood Duck likes wooded lakes and slow flowing rivers.
• Surface Feeders – Mandarin Ducks pick food from the water surface, rarely dive.
• Grassland grazers – Maned Duck and Wigeon tend to feed on grassland and crops close to water.
• Floating vegetation feeders – these birds feed amongst floating vegetation emerging from the water surface. Unfortunately named Pygmy Goose is actually a Duck. The Gadwall favours fresh water lakes and marshes. Some others known as Stiff-tail Ducks dive for food amongst floating vegetation. Ruddy, Maccoa and White-headed Ducks favour fresh water with fringe vegetation.
• Dabblers – are surface feeding birds which take plant materials on or just below the water surface. They are often seen up-ending and include African Black Duck, American Black Duck, Mexican Duck, Philippine Duck, Yellow-billed Duck and the Mallard. The Pacific Black Duck has been called the Mallard of Australasia.
• Other Dabblers are Pintails and Teal. The latter favour shallow waters in the northern hemisphere.
• Diving Ducks – take plant materials by diving to various depths below the surface. They include Pochards, Redhead, Hardhead, Ring-necked Duck, Scaup, Scoter and Tufted Duck.
• Coastal and Sea birds – are found in salt and brackish waters where they feed by diving. They include Eider, Harlequin and Goldeneye. The Harlequin winters along rocky coastal bays but breeds by fast flowing rivers. The Goldeneye likes to take aquatic insects but has a preference for waters which do not have insect eating fish which would compete for this food source.
Steamer Ducks are large, heavy, aggressive, diving ducks found in the coastal waters of South America and the Falkland Islands. They are reluctant fliers with spurs bare of feathers at the angle of the wing and are thought to be closely related to the Shelducks. They eat small marine animals taken from the sea bed.
• Fish pursuers – surprisingly only 6 species, the Smew and the Mergansers also known as Sawbills, dive and pursue fish as their main prey. The fish which are obviously available in the same habitat as the Ducks are probably taken by the more aggressive Coots which are also often present in the same habitat.
This group of Common Mergansers were photographed at Pennington Flash in the UK.
Concluding Remarks.
This group of birds are listed in families Anhimidae, Anseranatidae and Anatidae and account for 1.6% of the world's species.