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whooper swan

Cygnus cygnus

What do they look like?

Both male and female whooper swans have white feathers with black webbed feet and legs. Their beaks are orange-yellow at the base with a black tip. The markings on their beak are unique and can be used to tell them apart. In the spring and summer, adults may develop dark neck feathers because they are found in iron-rich environments. Juveniles have downy grey-brown feathers with a pink and black tipped beak. Adult whooper swans are large birds, with an average length of 1.4 to 1.65 m and a wingspan of 2.05 to 2.75 m. Male weights range from 7.4 to 14 kg with an average of 9.8 kg, which is much heavier than the female weight range of 8.2 to 9.2 kg. The highest recorded mass was 15.5 kg for a wintering male swan in Denmark. Aside from body mass, males also differ from females by their longer and thinner necks. A close relative of whooper swans are the smaller, shorter-necked Bewick swans. In addition, whooper swans have more orange-yellow beak markings while Bewick swans have more black markings. (Brazil, 2003; Dunning, 1992; Rees, et al., 1997)

  • Sexual Dimorphism
  • male larger
  • Range mass
    7.4 to 15.5 kg
    16.30 to 34.14 lb
  • Average length
    1.4 to 1.65 m
    ft
  • Average wingspan
    2.05 to 2.75 m
    ft

Where do they live?

Whooper swans (Cygnus cygnus) have a large range in the boreal areas of Eurasia and many nearby islands. Boreal conditions include cold winters and short summers. Whooper swans breed in Iceland, Ireland, and Great Britain and migrate in the winter to China, Korea, and Japan. Some migratory populations can be found in India and western North America. (Birdlife International, 2012; Brazil, 2003)

What kind of habitat do they need?

Whooper swans breed and set up nests along freshwater lakes, pools, shallow rivers, marshes, bogs, and swamps. They prefer areas where tall plants grow from the water, so they can hide their nests and newborns. In Iceland, they are found from sea-level to an elevation of 700 m. Non-breeding pairs of swans can be found near sheltered estuaries, lagoons, and shallow bays. Migrating whooper swans fly at altitudes of 500 to 1,700 m when crossing oceans, but they usually fly at lower levels so they can take breaks often. Near the British Isles, migrating whooper swans have been recorded flying above 8,000 m. (Brazil, 2003; Gardarsson and Skarphedinsson, 1984; Laubek, et al., 1999; Pennycuick, et al., 1996)

  • These animals are found in the following types of habitat
  • polar
  • freshwater
  • Terrestrial Biomes
  • taiga

How do they reproduce?

Whooper swans form lifelong breeding pairs. If their partner dies, whooper swans may find a new mate. These birds can be territorial during the breeding seasons. They can sometimes fight violently by beating their wings and either staring at the ground or head-plunging. These birds begin making mating displays mostly in the summer. Males and females often bob their heads up and down as a greeting and then, with bodies facing each other, turn their necks from left to right as they beat their wings. Before mating, they perform short displays by dipping their heads and thrusting their necks and chests into the water. Some pairs may preen each other after mating. (Brazil, 2003)

Whooper swans breed once a year, their breeding season begins from late April to early May. Some eggs are laid in late April, but most eggs are laid in May. Their eggs are large and elliptical with an off-white coloration. Older eggs may turn brown after several days due to nest conditions and iron-rich waters. A single clutch is laid per year, the size of the clutch depends on the age of the pair and the resources available at their nesting site. Younger pairs tend to lay smaller clutches. Nests are often found on large mounds near fresh water with vegetation for hiding. Egg incubation lasts about 30 to 32 days and hatching begins from June to early July. Not all pairs lay eggs, and not all eggs hatch. Cygnets, or young swans, are precocial and are covered with down feathers when they hatch, leaving the nest after 2 to 3 days. After three months, chicks begin to fledge and are able to fly at 78 to 96 days. Fledglings become independent after a year and become ready to mate after about 4 years, which is an uncommonly long time. Cygnet growth rates are impacted by habitat quality and food availability. (Black, 1996; Brazil, 2003)

  • How often does reproduction occur?
    Whooper swans breed once a year.
  • Breeding season
    These swans begin breeding in late April and early May.
  • Range eggs per season
    1 to 8
  • Range time to hatching
    30 to 32 days
  • Range fledging age
    78 to 96 days
  • Average time to independence
    1 years
  • Average age at sexual or reproductive maturity (female)
    4 years
  • Average age at sexual or reproductive maturity (male)
    4 years

After the first egg is laid, females incubate the eggs and males protect the nest and the rest of their territory. Swans have long incubation periods. Males do not usually incubate the eggs, but they keep the nest safe by staying within 50 to 100 m from the nest. Due to their large size, the eggs are able to stay warm even when the female needs to leave for short times to feed. Females take longer breaks as the eggs age and stop incubating altogether several days before the eggs hatch. The first few days after hatching, cygnets stay close to the nest where they are taken care of by the female. Unlike their close relative, trumpeter swans, whooper swans do not carry their young on their backs. Cygnets have high mortality rates due to cold weather, predators, and lack of food. Parents stay close to their cygnets and help them feed. Cygnets stay in shaded areas near their parents until they fledge. As the cygnets grow older, the parents begin spending less time protecting their young and more time feeding. In general, males protect the young before hatching and females protect the young before fledging. After fledging, but before independence, cygnets move further from their parents as they become more adventurous, although broods may stay together even after fledging. Interestingly, if an early freeze happens when cygnets are not yet able to fly, parents may leave their brood behind, which may result in the cygnets' death. Cygnets usually migrate with their parents until they are one year old, after that the parents restart the breeding cycle. (Brazil, 2003)

How long do they live?

Adult whooper swans can live for decades. They have a low yearly death rate once they are past the first few weeks after hatching. One common cause of death occurs when wild whooper swans decide to continue feeding off of agricultural cereal grains instead of migrating south to feed on aquatic vegetation. This shift may cause whooper swans freezing to death. However, the greatest cause of adult and juvenile deaths is the result of flying accidents. (Brazil, 2003)

  • Range lifespan
    Status: wild
    20 (high) years
  • Range lifespan
    Status: captivity
    25 (high) years
  • Typical lifespan
    Status: wild
    10 to 15 years
  • Typical lifespan
    Status: captivity
    12 to 16 years

How do they behave?

Whooper swans are territorial during the summer but social during the winter. Whooper swans can be found living in flocks near wetlands. Larger flocks of more than 40 birds are more common from October to November, whereas smaller flocks of fewer than 30 birds are more common from January to early spring. Whooper swans have a social hierarchy with larger families at the top, breeding pairs in the middle, and unpaired birds at the bottom. Dominant birds get to feed for the longest period of time, and birds often try to become part of a flock for added protection. Cygnets rarely initiate flight, but they perform pre-flight signals to communicate with their parents. (Brazil, 2003)

  • Range territory size
    0.7 to 5.7 km^2

Home Range

There is little information available regarding the territory size defended by whooper swans, although some estimates suggest that it is as low as 0.7 km2, while others suggest it is as high as 5.7 km2. Breeding pairs generally do not share a territory, however, in some circumstances several pairs have been found sharing the same small body of water. (Brazil, 2003)

How do they communicate with each other?

When it is time to leave a certain area, whooper swans make pre-flight signals such as 'head pumping', making 4 syllable calls, and wing flapping. Flocks continue to make the signals to build excitement so they can all take off together. Shortly after they land, whooper swans sometimes have greeting or triumph ceremonies, these include head bobbing, calling, and wing flapping. These interactions can sometimes turn into aggressive or mating behaviors. Aggression is shown by a combination of ground staring, where the neck is arched and wings are spread slightly, bow-spitting, where the neck is held forward, and carpal flapping, where the wings flap quickly. In the case of competition between whooper swans, a 'water-boiling' display may occur, in which both swans outstretch their wings before they attack each other. (Brazil, 2003)

What do they eat?

Whooper swans feed in shallow water and eat aquatic plants and roots. Cygnets eat small insects and other invertebrates. In shallow fresh waters, whooper swans use their webbed feet to dig in the mud and dip their head into the water to feed on shallow roots and tubers. Parents also help cygnets feed by stirring up the water to make aquatic plants easy to reach. Whooper swans can also feed on land or near saltwater environments. In freshwater areas, whooper swans mostly feed in the morning and afternoon. In saltwater areas, whooper swans mostly feed between the morning and afternoon. Feeding is harder during high tide, so whooper swans mostly rest at high tide and feed during low tide. On land, these birds feed based on day length, temperature, and safety. When days are short, cold, and dark, whooper swans forage less compared to longer, warmer, and brighter days. In areas with farming, such as Denmark and northern Germany, whooper swans feed on crops during the winter. In central Scotland, swans that feed on farm land eat leftover grains in autumn and eat grass from mid-winter until spring. Most whooper swans eat freshwater roots, stems, and leaves, although some swans also eat mussels. (Brazil, 2003)

  • Animal Foods
  • fish
  • insects
  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • seeds, grains, and nuts

What eats them and how do they avoid being eaten?

Resting whooper swans are able to curl up on the ground to protect themselves from the cold while watching for predators. Predators often attack clutches by stealing one egg at a time when parents take incubation breaks to feed. These swans are less likely to be preyed on once they reach their adult size. When whooper swans are young, they are more vulnerable to predators and stay close to their parents for protection. Due to their larger size, whooper swans are not very graceful on land and usually hide in the water from predators. (Brazil, 2003)

What roles do they have in the ecosystem?

Whooper swans impact the structure of the plant communities where they feed. Their nests may be parasitized, meaning other bird species lay their eggs in whooper swan nests, such species include greylag geese and red-crested pochard birds. (Brazil, 2003; Kiorboe, 1980; Sandsten and Klaassen, 2008)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

Some whooper swans feed on crop plants, this may negatively impact farmers whose crops may be damaged. In addition, the avian influenza virus H5N1 was found on the eyelids of a whooper swan during the 2010 H5N1 outbreak in Japan. Whooper swans may be disease carriers due to their wide ranged migratory habits. (Brazil, 2003; Bui, et al., 2013)

  • Ways that these animals might be a problem for humans
  • injures humans
    • carries human disease
  • crop pest

How do they interact with us?

In the past, whooper swans have been hunted but they are usually unafraid of humans and will take food directly from a human's hand, this happens mainly during the winter when food is scarce. Their friendliness has drawn crowds of people and tourists who come to admire their beauty and signature whooping calls. (Brazil, 2003)

Are they endangered?

Human habits that threaten whooper swans include hunting, egg poaching, and habitat destruction. There have been efforts to preserve popular wetland sites from Iceland to China and laws that make hunting the swans illegal in Russia. Currently the species is considered one of “least concern.” (Birdlife International, 2012; Brazil, 2003)

Contributors

Priscilla Kuo (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

References

Birdlife International, 2012. "IUCN Red List of Threatened Species" (On-line). Cygnus cygnus. Accessed October 25, 2013 at http://www.iucnredlist.org/details/22679856/0.

Black, J. 1996. Partnerships in Birds. Oxford: Oxford University Press.

Brazil, M. 2003. The Whooper Swan. London: T & AD Poyser.

Bui, V., H. Ogawa, L. Ngo, T. Baatartsogt, L. Abao, S. Tamaki, K. Saito, Y. Wantanabe, J. Runstadler, K. Imai. 2013. H5N1 highly pathogenic avian influenza virus isolated from conjunctiva of a whooper swan with neurological signs. Archives of Virology, 158: 451-455.

Dunning, J. 1992. CRC Handbook of Avian Body Masses. Boca Raton: CRC Press.

Gardarsson, A., K. Skarphedinsson. 1984. A census of the Icelandic whooper swan population. Wildfowl, 35: 27-47.

Kiorboe, T. 1980. Distribution and production of submerged macrophytes in Tipper Grund (Ringkobing Fjord, Denmark), and the impact of waterfowl grazing. Journal of Applied Ecology, 17: 675-687.

Laubek, B., L. Nilsson, M. Wieloch, K. Koffijberg, C. Sudfeldt, A. Follestad. 1999. Distribution, numbers and habitat choice of the NW European whooper swan Cygnus cygnus population: results of an international census in January 1995. Vogelwelt, 120: 141-154.

Pennycuick, C., O. Einarsson, T. Bradbury, M. Owen. 1996. Migrating whooper swans Cygnus cygnus: satellite tracks and flight performance calculations. Journal of Avian Biology, 27: 118-134.

Rees, E., O. Einarsson, B. Laubek. 1997. Cygnus cygnus whooper swan. BWP Update, 1: 27-35.

Sandsten, H., M. Klaassen. 2008. Swan foraging shapes spatial distribution of two submerged plants, favouring the preferred prey species. Oecologia, 156: 569-576.

 
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Kuo, P. 2014. "Cygnus cygnus" (On-line), Animal Diversity Web. Accessed August 19, 2019 at http://www.biokids.umich.edu/accounts/Cygnus_cygnus/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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