Black-necked swans are native to south coastal South America and inland lakes in the Neotropical region. Black-necked swans breed in Patagonia, Tierra del Fuego, and the Falkland Islands. In winter they migrate northward to Paraguay and southern Brazil.

Biogeographic Regions: neotropical (Native )

Black-necked swans are the smallest members of the genus Cygnus, ranging in length from 102 cm to 124 cm. Males range in mass from 4.5 kg to 6.7 kg, and females from 3.5 to 4.4 kg. Wingspan also differs between the sexes, where male wingspan range is 435 to 450 mm, in females it is 400 to 415 mm. Black-necked swans have a relatively high basal metabolism of 3680.56 cm^3 oxygen/hour. Cygnus melanocoryphus has a white body with a distinct long, velvet black neck and head, which distinguishes it from other swans. The neck and head also may have white speckles. The bluish-gray bill has a scarlet base with a large, double-lobed, red caruncle that rests on the base under the eyes. They have a white stripe behind the eyes that extends towards the back of the neck and the windpipe is unconvoluted (has only a slight bend). Black-necked swans have an elevated hind toe, a thin coat of feathers, and pointed wings. The legs are pink, very short, and have unusual positioning, making it hard for these swans to walk on land. The wings are covered in white feathers. Males are usually one-third larger than females, but are monomorphic in shape and color except for their considerably shorter necks. Cygnets (the young) are dull, light brownish-gray in color and have black bills and feet; they obtain their black neck and white body coat in their second year of life.

Range mass: 3500 to 6700 g.

Range length: 102 to 124 cm.

Range wingspan: 400 to 450 mm.

Average basal metabolic rate: 3680.56 cm^3 oxygen/hour.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike; male larger

• Terrestrial
• Freshwater
• Marine

Habitats preferred by black-necked swans are shallow coastal areas along the Pacific Ocean, inland lakes, lagoons, estuaries and marshes. Especially important are areas rich with submergent vegetation. They are recorded from sea level to 1200 m elevation.

Range elevation: 0 to 1200 m.

Habitat Regions: temperate ; saltwater or marine ; freshwater

Aquatic Biomes: lakes and ponds; coastal ; brackish water

Wetlands: marsh

Other Habitat Features: estuarine

Black-necked swans feed mainly on aquatic vegetation, most often from the bottom of ponds. They have strong bills with serrated edges and a nail at the tip. The surface of the tongue is spinous, which aids in grasping and tearing plants. Also, horny serrations in the bill help to filter small food items from the water surface. This species is mainly vegetarian, feeding mostly on stonewarts (Characeae), pondweeds (Potamogeton), milfoil (Myriophyllum), wild celery (Vallisneria), and other waterweeds. They will also eat some invertebrates, like insects and rarely fish or frog spawn.

Animal Foods: amphibians; fish; insects; other marine invertebrates; zooplankton

Plant Foods: leaves; bryophytes; algae; macroalgae ; phytoplankton

Foraging Behavior: filter-feeding

Primary Diet: herbivore (Folivore , Algivore)

Two Trichobilharzia species have been found in the nasal cavities of swans, which cause neuromotor problems. Schistosomula of both nasal and visceral Trichobilharzia species are able to develop and migrate for several days in a non-specific mammalian host, so humans are warned not to expose themselves to waters with dense swan populations and probably Trichobilharzia cercaria populations. Other species that use C. melancoryphus as a host are a gape-worm (Cyathostoma bronchialis), feather lice (Mallaphaga) and roundworm larvae (Echinuria uncinata). Gape-worms may cause pneumonia in young birds, often leading to death. Feeding on aquatic vegetation, C. melancoryphus controls algal populations in lakes such that they don't become invasive species in the environment. Black-necked swans may act as a keystone species for the management of these aquatic plants.

Ecosystem Impact: keystone species

Commensal/Parasitic Species:

• Trichobilharzia cercariae
• Cyathostoma bronchialis
• Mallaphaga
• Echinuria uncinata

Adults have few natural predators, but gulls are a threat to eggs and chicks. Minks and foxes also prey on small cygnets. Humans are considered predators when swans are hunted for food, game, and feathers or quills.

Known Predators:

• gulls (Larus)
• minks (Martes)
• foxes (Vulpes)
• humans (Homo sapiens)

Courting rituals, flight arrangement, and parental care all use visual communication. Swans signal to other members of the flock or a family unit by dipping the head or flapping the wings to suggest direction or the beginning of a triumph ceremony for mating. This species also uses tactile stimulation to communicate, such as grooming and bathing processes. Females groom young cygnets to teach them how to clean themselves and a bathing ritual is used after copulation to cement the pair-bond. Unlike most other swans, C. melancoryphus does not squawk or honk. Instead they use weak whistles to communicate. Black-necked swans are usually silent, but males give repeated hollow whining sounds, females are more melodious. The typical call for communication is a weak, wheezy whistle uttered both on water and in flight, but does not carry far.

Communication Channels: visual ; tactile ; acoustic

Other Communication Modes: duets ; choruses

In the wild, C. melancoryphus is expected to live between 10 and 20 years, which a record age of 30 years. In captivity, the average age for a black-necked swan is 6.8 years, but they can live up to 20 years. Typical causes of mortality include disease, predation on cygnets, and lack of food. Black-necked swans also suffer from lead poisoning from incidental ingestion of lead shot from guns used for hunting in the wetlands they inhabit.

Range lifespan

Status: wild: 30 (high) years.

Typical lifespan

Status: wild: 121.67 to 243.33 months.

Typical lifespan

Status: captivity: 20 (high) years.

Average lifespan

Status: captivity: 6.8 years.

Black-necked swans are monogamous and males and females mate for life. If one of them should die, the surviving mate will find a new mate. Breeding season begins in July and extends to September and November. Swans are known to have triumph ceremonies, which occur when a male attacks a rival suitor, then returns to his potential mate to perform an elaborate courtship ceremony while posturing and calling. Both males and females rhythmically dip their heads into the water and then stretch their necks upwards while swimming around each other. The triumph ceremony has no wing-raising and consists predominantly of calling and lifting of the chin. After copulation, there is no display of mating behavior except for habitual bathing. A nest is built in thick reed beds around the edges of bodies of water. The swan brings material to the site, such as rushes (vegetation) and aquatic plants, in order to build the large structure that partially floats. The cob is quite protective of his pen and her eggs and guards the nest for long periods of time. The monogamous behavior affects the care of cygnets such that the young have been known to ride on their parent's back.

Mating System: monogamous

Black-necked swans breed between July and the autumn months. They can breed as many as three times during the mating season. Clutch sizes range from 3 to 7 eggs, with the mean being 4.6 eggs. It takes between 34 and 37 days for an egg to hatch, with the average being 35 days. Typically, eggs are between 101 x 66 mm in size and weigh approximately 238 gm. Fledging takes place within 10 weeks of hatching and each cygnet stays with its parents for 8 to 14 months before it is independent. Once a cygnet has reached the age of two (average), it is sexually mature and is able to mate. Even though the swans are mature at this age, they do not form pair bonds until they are three years old. Offspring stay with parents until the following summer, and may stay as long as the next winter season.

Breeding interval: There is one mating season per year but black-necked swans can lay up to three times each breeding season.

Breeding season: The breeding season for C. melancoryphus is between July and September to November at the latest.

Range eggs per season: 3 to 7.

Average eggs per season: 4.6.

Range time to hatching: 34 to 37 days.

Average time to hatching: 35 days.

Average fledging age: 70 days.

Range time to independence: 8 to 14 months.

Average age at sexual or reproductive maturity (female): 2 years.

Average age at sexual or reproductive maturity (male): 2 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

During the incubation period, males are very protective of the nest and defend the territory surrounding the eggs. Although both parents are known to carry the young on their backs, the male usually takes over this responsibility after hatching so the female can concentrate on feeding; she must regain the weight she lost during incubation. Both parents provide the hatchlings with food and protection from predators. Females remain very close to cygnets during their foraging. Although vigorous in their use of wings and beak against attack from other animals, black-necked swans panic at the sight of humans and frequently leave their nests without covering their eggs.

Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Protecting: Male, Female); post-independence association with parents

Cygnus melancoryphus populations seem to be stable currently.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Human microsporidiosis, a serious disease of immunocompetent and immunosuppressed people, can be due to zoonotic and environmental transmission of microsporidian spores. The prevalence of microsporidian infections in waterfowl is significantly higher than in other birds. Waterborne microsporidian spores of species that infect people can originate from common waterfowl, like C. melancoryphus, which have unlimited access to surface waters, including waters used for production of drinking water.

Negative Impacts: injures humans (causes disease in humans )

Swans were a source of food for native peoples of the world, but are seldom hunted currently. Due to the relatively calm nature of C. melancoryphus, they are a valuable breeding bird. There is a large pet trade in this species. Since they have a healthy population in South America and are not endangered, humans have been able to export C. melancoryphus to North America. Also, tourism is highly encouraged to the Falkland Islands just to witness the sight of this species, promoting the tourist industry. Swans control algal populations, improving water quality.

Positive Impacts: pet trade ; food ; ecotourism