Tundra swan (Bewick's swan & Whistling swan)

Cygnus columbianus

Toendrazwaan (Kleine zwaan & Fluitzwaan)

The Tundra Swan (Cygnus columbianus) is a small Holarctic swan. The two taxa within it are usually regarded as conspecific, but are also sometimes split into two species, Cygnus bewickii (Bewick's Swan) of the Palaearctic and the Whistling Swan, C. columbianus proper, of the Nearctic. Birds from eastern Russia (roughly east of the Taimyr Peninsula) are sometimes separated as the subspecies C. c. jankowskii, but this is not widely accepted as distinct, most authors including them in C. c. bewickii. Tundra Swans are sometimes separated in the genus Olor together with the other Arctic swan species.

Bewick's Swan is named after the engraver Thomas Bewick, who specialised in illustrations of birds and animals.

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

The global population is estimated to number > c.300,000 individuals (Wetlands International 2006), while national population sizes have been estimated at c.50-10,000 wintering individuals in China and c.100-10,000 breeding pairs in Russia (Brazil 2009).

More information: http://www.iucnredlist.org/details/100600371/0

Tundra swan determination: https://observation.org/soort/info/243796 

Bewick's swan, Cygnus (columbianus) bewickii

In 1964, Sir Peter Scott realised that each individual Bewick's swan could be identified by the unique pattern of yellow and black on its bill, and so started one of the longest-running single species studies in the world.

More information anbout this study can be found here: 
http://www.wwt.org.uk/conservation/saving-wildlife/science-and-action/uk-species/bewicks-swan/ 

Above: Cygnus columbianus bewickii or Bewick's swan

Above: Cygnus columbianus bewickii or Bewick's swan

Above: Juvenile Cygnus columbianus bewickii or Bewick's swan

Above: Handling a Bewick's swan

Above: Bewick's swan, female

Above: a pair of Bewick's swans, male right

Above: Bewick's swan with very light coloured iris.

Above: Bewick's swan with dark (normal) coloured iris.

Above: a breeding pair of Bewick's swans and four juveniles.

Above: Bewick's swans at the Wildfowl & Wetlands Trust, Slimbridge, UK

Above: Bewick's swan at the Wildfowl & Wetlands Trust, Slimbridge, UK

Above: Bewick's swans in aviculture (two locations).

Above: Bewick's swan in aviculture (footage by Jurre Brenders)

Whistling swan, Cygnus (columbianus) columbianus

Above: Cygnus columbianus columbianus or Whistling swan

Above: Cygnus columbianus columbianus or Whistling swan (courtship)

Above: Cygnus columbianus columbianus or Whistling swan (courtship)

Above: Cygnus columbianus columbianus or Whistling swan (breeding)

Above: Cygnus columbianus columbianus or Whistling swans (different bill-patterns)

Above: male whistling swan

Above: a pair of whistling swans in courtship (male right)