University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Ducks, Geese, and Swans of the World by Paul A. Johnsgard Papers in the Biological Sciences 2010 Ducks, Geese, and Swans of the World: Tribe Anserini (Swans and True Geese) Paul A. Johnsgard University of Nebraska-Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/biosciducksgeeseswans Part of the Ornithology Commons Johnsgard, Paul A., "Ducks, Geese, and Swans of the World: Tribe Anserini (Swans and True Geese)" (2010). Ducks, Geese, and Swans of the World by Paul A. Johnsgard. 5. https://digitalcommons.unl.edu/biosciducksgeeseswans/5 This Article is brought to you for free and open access by the Papers in the Biological Sciences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Ducks, Geese, and Swans of the World by Paul A. Johnsgard by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Tribe Anserini (Swans and True Geese) MAP 10. Breeding (hatching) and wintering (stippling) distributions of the mute swan, excluding introduced populations. Drawing on preceding page: Trumpeter Swan brownish feathers which diminish with age (except MuteSwan in the Polish swan, which has a white juvenile Cygnus alar (Cmelin) 1789 plumage), and the knob over the bill remains small through the second year of life. Other vernacular names. White swan, Polish swan; In the field, mute swans may be readily iden­ Hockerschwan (German); cygne muet (French); tified by their knobbed bill; their heavy neck, usu­ cisne mudo (Spanish). ally held in graceful curve; and their trait of swim­ ming with the inner wing feathers raised, especially Subspecies and range. No subspecies recognized. in males. In flight, the wings produce a loud "sing­ Breeds under native wild conditions in southern ing" noise, but apart from hissing and snorting Sweden, Denmark, northern German, Poland, sounds this species is relatively "mute." and locally in Russia and Siberia; also in Asia Minor and Iran east through Afghanistan to In­ ner Mongolia; in winter to northern Africa, the Black Sea, northwestern India, and Korea. NATURAL HISTORY Breeds locally feral or semiferal in Great Britain, France, Holland, and Central Europe. Introduced Habitat and foods. The habitats of this species are and locally established in North America, mainly diverse and numerous, as a reflection of a long as­ on Long Island and in northern Michigan. Also sociation with man and at least partial domestica­ locally established in South Africa, Australia, tion. Probably, however, Temperate Zone marshes, and New Zealand. See Map 10. slowly flowing rivers, and lake edges were its native habitats. Clean, weed-filled streams are Measurements and weights. (Mostly from Scott & preferred over larger, polluted rivers. Brackish or Wildfowl Trust, 1972.) Folded wing: males, salt-water habitats are often used during non­ 589-622 mm; females, 540-96 mm. Culmen: breeding periods. A variety of studies of foods males, 76-85 mm; females, 74-80 mm. Weights: taken in Europe and North America indicate that males, 8.4-15.0 kg (av. 12.2 kg); females, the leafy parts of a number of fresh-water or salt­ 6.6-12.0 kg (av. 8.9 kg). Eggs: avo 115 x 75 mm, water plants, such as pondweeds, muskgrass, eel­ greenish blue, 340 g. grass (Zostera), and green algae (Enteromorpha), Identification and field marks. Length 50-61" are major sources of food where they are available. (125-55 cm). Plate 8. Adults are entirely white in Also where it is available, waste grain is often con­ all post juvenile plumages. The bill is orange, with sumed, and some grazing on terrestrial grasses near black around the nostrils, the nail, and the edges of water is prevalent in many areas (Scott & Wildfowl the mandible. The feet are black, except in the un­ Trust, 1972). Mute swans can reach underwater common "Polish" color phase, which has fleshy­ foods up to 50 centimeters below the surface by gray feet. Females are smaller (see measurements upending, but in common with other swans do not above) and have a less well developed knob over dive when foraging. A small amount of animal the bill. Juveniles exhibit a variable number of foods, including amphibians, worms, mollusks, and insects, may be taken when available, but these are minor parts of their diet. Social behavior. Except in a few areas where local foraging conditions favor large concentrations, as on some coastal islands, mute swans are not nota­ bly social. Nevertheless, they may flock in groups of a thousand or more in summer molting areas, and similar flocking may also occur in the winter. In many parts of its range the mute swan is essen­ tially sedentary, and in England, for example, studies of banded birds have revealed that most movements are less than 30 miles, and usually follow watercourses (Ogilvie, 1967). Probably the most extensive migrations occur in the breeding ••• 29 birds of Siberia and Mongolia, from Lake Baikal flocks, and consists of mutual head dipping and east. It is presumably those birds that winter along preening or rubbing movements along the flanks the Pacific coast, from Korea south to the Yangtze and back. After treading, both birds rise in the Kiang, suggesting a migration of up to about 1,000 water breast to breast, calling and extending their miles. Pairs and family units migrate together and necks and bills almost vertically for a brief mo­ remain together until about the end of the year, ment, then subside in the water (Johnsgard, 1965a). when at least in England the breeding adults begin Once formed, pair bonds are very strong, and so to exhibit territorially. At that time the young birds long as both members of a pair remain alive there remain in the winter flocks of nonbreeding birds, is a low rate of mate changing. One study in and they may remain together through the follow­ England indicated that there was a 3 percent JI di­ ing summer and winter (Scott & Wildfowl Trust, vorce" rate among unsuccessful breeders or non­ 1972). breeders (Minton, 1968). Pair-forming behavior occurs in the fall and winter, usually in the season before breeding initi­ Reproductive biology. The nesting period of mute ally. Among mute swans, initial breeding is most swans is in spring, which is generally March frequent in the third year, with some birds (mostly through June in its Northern Hemisphere range, females) breeding when two years old and some and from September through January in New not until four or older. Pair formation and pair Zealand and Australia. Mute swans are highly ter­ bonding in this as in all typical swans occurs by ritorial, although the size of the territory varies mutual greeting ceremonies such as head turning, with breeding density. One study in Staffordshire, and bonds are firmly established by triumph cere­ England, indicated a density of a pair per 2,000 monies between members of a pair. This occurs hectares, but with territories limited to a few after the male has threatened or attacked an meters of stream-side locations. In a few areas of Jlenemy" and returned to his mate or prospective dense colonies, the nests may be located only a few mate with ruffled neck feathers and raised wings, meters apart. In England, nests are most often calling while chin lifting. Precopulatory behavior placed in or near standing water, less often beside may occur frequently among paired birds in winter running water, and least often in coastal situations. 30 ••• Nests are large piles of herbaceous vegetation, built Measurements and weights. (Mainly from Frith, by both sexes, and often built on the previous 1967.) Folded wing: males, 434-543 mm; fe­ year's nest, especially if it was a successful site. males, 416-99 mm. Culmen: males, 57-79 mm; Eggs are deposited every other day until a clutch of females, 56-72 mm. Weights: males, 4.6-8.75 kg 4 to 8 (usually 5 or 6) eggs is laid. Incubation is (av. 6.27 kg); females, 3.7-7.2 kg (av. 5.1 kg). normally performed only by the female ("pen"), Eggs: avo 115 x 65 mm, pale green, 300 g. but the male ("cob") may occasionally take over Identification and field marks. Length 45-55" for a time. The incubation period is usually 35-36 (115-40 cm). Plate 9. This is the only black swan; days, during which time the male rarely strays far adults are uniformly dark brownish black, with from the nest. After hatching, both sexes atten­ somewhat paler underparts and white flight feath­ tively care for the young, frequently allowing them ers. All the primaries and the outer secondaries are to ride on their backs. The rate of growth is very white, while the inner secondaries are white-tipped. slow, and the fledging period is from 120 to 150 The innermost wing feathers are strongly undu­ days, during which time the adults undergo their lated. The bill is red to orange, with a whitish postnuptial molt. Thereafter, the family increases subterminal bar and nail; the iris is reddish (or their food intake and fat reserves before leaving the sometimes whitish), and the feet and legs are black. breeding grounds (Kear, in Scott & Wildfowl Females are smaller and have a less brightly col­ Trust, 1972). ored bill and iris. Also, they appear to have shorter Status. This swan has in general benefited from neck feathers and a less ruffled back, which may man's influence, and has either been purposefully in­ simply be the result of variable feather lifting. troduced or otherwise spread into new breeding Juveniles are a mottled grayish brown, with light­ areas in historical times.