Bucephala clangula

Bucephala clangula

The common goldeneye or simply goldeneye (Bucephala clangula, Linnaeus 1758) is a bird belonging to the Anatidae family.

Systematic –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Animalia,
Phylum Chordata,
Aves class,
Order Anseriformes,
Family Anatidae,
Subfamily Anatinae,
Mergini Tribe,
Genus Bucephala,
Species B. clangula.
The terms are synonymous:
– Anas clangula (Linnaeus, 1758)
– Anas glaucion Linnaeus, 1758;
– Clangula chrysophthalmos;
– Clangula glaucion (Linnaeus);
– Fuligula clangula;
– Glaucionetta clangula (Linnaeus, 1758);
– Nyroca clangula (Linnaeus, 1758).
The following subspecies are recognized within this species:
– Bucephala clangula subsp. americana (Bonaparte, 1838);
– Bucephala clangula subsp. clangula (Linnaeus, 1758).

Geographic Distribution and Habitat –
The Bucephala clangula is a Holarctic duck distributed in Europe, Asia and North America. The nesting area covers the northern band of the northern hemisphere. The European population frequents southern Europe and the Mediterranean basin exclusively in the winter period.
In Italy, some significant concentrations are known in the coastal strip of the upper Adriatic in particularly harsh winters.
Its nesting habitat is the taiga. They are found in lakes and rivers of boreal forests from Canada and the northern United States to Scandinavia and northern Russia. They are migratory and most winter in sheltered coastal waters or open continental waters at more temperate latitudes. They generally nest in the cavities of large trees. They also readily use nest boxes, which have made it possible for these birds to establish a healthy, breeding population in Scotland, where they are slowly increasing and spreading with the help of nest boxes. In winter they are usually quite common around the lakes of Brittany and some have been encouraged to nest in specially placed nest boxes to try to establish them there throughout the year.

Description –
The Bucephala clangula is a medium-sized sea duck with a length of 40-52 cm, a wingspan of 65-80 cm and a weight ranging between approximately 500 and 1200 grams.
There is sexual dimorphism with adult males measuring 45–52 cm and weighing from 888 to 1400 grams, while females measuring 40–50 cm and weighing from 500 to 1182 grams.
Adult males have a dark head with greenish reflections and a white circular spot under the eye, a dark back and a white neck and belly.
Adult females have a brown head and a predominantly gray body.
The head is polygonal and the beak rather short.
The male’s nuptial plumage is black and bright white with a large white oval spot on the black head; eclipse dress with narrow white collar (absent in young people).
The down is black with white spots.
The legs are orange-red and the eyes are golden-yellow.
The average size of an egg is a width of 43.3 mm, a length of 59.3 mm and a weight of 64 grams, with a bluish color.
In flight the flaps of the wings produce a melodious noise.
The male’s voice is a “qui ric”, that of the female a “garr gra” or others.

Biology –
The Bucephala clangula reproduces in the spring period with nesting in the months of April-May. During the parade the male keeps his neck erect.
The nest is built in tree hollows up to 20 meters high, or in artificial nests.
The clutch is 6-11 eggs, which are light blue in colour, almost round immersed in a mass of whitish fluff.
The incubation period varies from 28 to 32 days. The female carries out all the incubation alone and is abandoned by the male 1 or 2 weeks after the start of incubation. The young remain in the nest for approximately 24-36 hours. Brood parasitism is quite common and is carried out both against other golden-eyes and those of other species of ducks and, mixed with golden-eye eggs, even tree swallow and European starling eggs have been found. Litters normally begin to mix with those of other females and become increasingly independent. There are known cases of chicks that have been killed by other mothers or by other birds that competed with them.
The young are able to fly at 55-65 days of age.

Ecological Role –
The Bucephala clangula is a diving bird that feeds underwater. Throughout the year, about 32% of their prey are crustaceans, 28% are aquatic insects and 10% are molluscs. Insects are the predominant prey during nesting, and crustaceans are the predominant prey during migration and winter. Locally, fish eggs and aquatic plants can be important foods.
In turn, these birds can become prey to various hawks, owls and eagles, while females and their broods have been preyed upon by bears (Ursus spp.), various weasels (Mustela spp.), mink (Mustela vison), raccoons ( Procyon lotor) and also the northern flicker (Colaptes auratus) and the American red squirrel (Tamiasciurus hudsonicus).
It is a migratory species in March-April and September-November.
As with other species, this bird has also been, especially in the past, an object of hunting.
In North America during the 1970s approximately 188,300 ducks were killed by duck hunters, which represents approximately 4% of the total number of ducks killed in that region during that period. Nowadays the percentage is probably the same. Both the nesting and wintering habitat of these birds has been damaged by neglect and pollution. However, this is the only duck in North America to have benefited in the short term from lake acidification.
This duck is one of the species to which the Agreement on the Conservation of Afro-Eurasian Migratory Waterbirds (AEWA) applies.
Both the breeding and winter habitats of these birds have been degraded by clearing and pollution, although this species, as mentioned, benefits in the short term from lake acidification in North America.

Guido Bissanti

Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– C.Battisti, D. Taffon, F. Giucca, 2008. Atlas of nesting birds, Gangemi Editore, Rome.
– L. Svensson, K.Mullarney, D. Zetterstrom, 1999. Guide to the Birds of Europe, North Africa and the Near East, Harper Collins Publisher, United Kingdom.

Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/250667454/original.jpg