Eurasian siskin

Appearance

The siskin is a small, short-tailed bird, 11–12.5 centimetres in length with a wingspan that ranges from 20–23 centimetres. It weighs between 10–18 grams.

The bird's appearance shows sexual dimorphism. The male has a greyish green back; yellow rump; the sides of the tail are yellow and the end is black; the wings are black with a distinctive yellow wing stripe; its breast is yellowish becoming whiter and striped towards the cloaca; it has a black bib and on its head it has two yellow auriculas and a black cap. The amount of black on the bib is very variable between males and the size of the bib has been related to dominance within a flock. The plumage of the female is more olive-coloured than the male. The cap and the auriculas are greenish with a white bib and a rump that is a slightly striped whitish yellow. The young have a similar colouration to the females, with drab colours and a more subdued plumage.

The shape of the siskin's beak is determined by its feeding habits. It is strong although it is also slender in order to pick up the seeds on which they feed. The legs and feet are dark brown and the eyes are black.

It has a rapid and bounding flight pattern that is similar to other finches.

The siskin is easy to recognize, but in some instances it can be confused with other finches such as the citril finch, the greenfinch or the European serin. Whereas the European siskin, in many plumages, is a bright bird, the pine siskin in its typical morph is a drab by comparison. Adult male European siskins are bright green and yellow with a black cap, and an unstreaked throat and breast; the pine siskin does not have a corresponding bright plumage. Adult female European siskins also usually have green and yellow plumage tones: for example, yellow in the supercilium and on the sides of the breast, green tones in the mantle and yellow in the rump. Adult pine siskins of the typical morph do not have green and yellow tones, although juveniles can have a yellowish-buff wash on their underparts and buff-toned wingbars, for a short period prior to their autumn migration. The ground colour of the underparts of European siskin is normally pure white, whereas on pine siskin it is usually a dirtier colour. In female and juvenile European siskin, the centre of the belly and lower breast are often largely or entirely unstreaked, whereas in most pine siskins the streaking extends across the whole of the underparts. The wingbars of European siskin are broad and yellow whereas they are normally narrower and buffish-white in pine siskin, contrasting with the bright yellow flash at the base of the primaries. Pine siskins have a longer bill, usually with a straight culmen, compare with a short bill in European siskin, with a decurved culmen. There is a green morph of pine siskin which is closer in appearance to European siskin; these birds make up only 1% of the population. These are closer in appearance to female European siskin, but differ in that they have a yellow-wash on the undertail-coverts, no yellow in the supercilium, reduced underparts streaking, and much yellow at the base of the tail and remiges; there may also be a difference in the extent of yellow in the underparts but this needs further study.

Naming

It is also called the European siskin, common siskin or just siskin. Other names include "Black-headed Goldfinch", "barley bird" and "aberdevine".

Distribution

This species can be found across the greater part of Eurasia and the north of Africa. Its breeding area is separated into two zones, each side of the Palearctic ecozone: the east coast of Asia and the central and northern part of Europe.

These birds can be found throughout the year in Central Europe and some mountain ranges in the south of the continent. They are present in the north of Scandinavia and in Russia and they over-winter in the Mediterranean basin and the area around the Black Sea. In China they breed in the Khingan Mountains of Inner Mongolia and in Jiangsu province; they spend summer in Tibet, Taiwan, the valleys of the lower Yangtse River and the south east coast.

The Eurasian siskin is occasionally seen in North America. There is also a similar and closely related North America counterpart, the pine siskin, "Spinus pinus".

Their seasonal distribution is also marked by the fact that they follow an anomalous migration pattern. Every few years they migrate southwards in larger numbers and the overwintering populations in the Iberian Peninsula are greatly augmented. This event has been the object of diverse theories, one theory suggests that it occurs in the years when Norway Spruce produces abundant fruit in the centre and north of Europe, causing populations to increase. An alternative theory is that greater migration occurs when the preferred food of alder or birch seed fails. This species will form large flocks outside the breeding season, often mixed with redpolls.

Status

The worldwide population of the siskin is estimated as between 20 and 36 million. The European population is estimated as between 2.7 and 15 million pairs. There does not seem to be a major decline in population numbers and for this reason the IUCN has listed their conservation status as Least Concern. The siskin appears in Annex II of the Berne Convention as a protected bird species.

Behavior

They are very active and restless birds. They are also very social, forming small cohesive flocks especially in autumn and winter. They are fairly trusting of humans, it being possible to observe them from a short distance. During the breeding season, however, they are much more timid, solitary and difficult to observe. For this reason there is a German legend which says that siskins guard a magic stone in their nests that makes them invisible. It is one of the few species which has been described as exhibiting "allofeeding"' behavior, this is where subordinates regurgitate food for the dominant members of the group, which creates a strong cohesion in the flocks and implies a hierarchical structure within the group.

Habitat

It is a bird that does not remain for long in one area but which varies the areas it used for breeding, feeding, over-wintering from one year to the next.

Its habitat is forested areas at a particular altitude on a mountain side and they have a certain predilection for humid areas. Coniferous woodland, especially Spruce, is favoured for breeding. It builds its nest in a tree, laying 2–6 eggs. The British range of this once local breeder has expanded greatly due to an increase in commercial conifer plantations. The siskin also breeds in mixed woodland; while in winter they prefer stubble and crops and areas containing trees with seeds.

Reproduction

Pairs are generally formed during the winter period before migration. The males compete aggressively for the females. As part of the courtship the male plumps up the feathers of the pileus and rump, making itself bigger, extending the tail and singing repeatedly. They also make mating flights from tree to tree, although they are not as eye-catching as the flights of the other finches. They construct a nest that is generally located at the end of a relatively high branch in a conifer, such that the nest is reasonably hidden and difficult to see. On the Iberian Peninsula they make their nests in "afirs," Scotch pine and Corsican pine. They form small colonies of up to six pairs with the nests located near to each other. The nest is small and bowl-shaped. It is made from small twigs, dried grasses, moss and lichen and lined with down.

The first brood is born in mid-April. The female lays between 2 and 6 eggs. The eggs are white or light grey or light blue, with small brown spots and they are approximately 16.5mm by 12mm in size. Incubation takes between 10 and 14 days and is carried out entirely by the female. The chicks are altricial and nidicolous. They leave the nest after 15 days in a semi-feathered condition. They then remain close to the nest area for up to a month when, with their plumage now complete, they disperse. The siskin usually has a second brood, from the middle of June up to the middle of July.

Food

The siskin is mainly a granivore although it varies its diet depending on the season. It feeds in trees avoiding eating on the ground.

In autumn and winter its diet is based on the seeds of deciduous trees such as birch and above all alder. They also visit cultivated areas and pasture where they join with other finches in eating the seeds of various "Compositae" such as thistles, dandelions, "Artemisia", knapweeds and other herbaceous plants such as St. John's wort, meadowsweet and sorrel.

In spring, during the breeding season, they are found in coniferous forests. At this time their feeding is based on the seeds of these trees, especially on trees belonging to the genera "Abies", "Picea" and "Larix". They also feed on elms and poplars. When feeding the young they eat more insects, mainly beetles, as the proteins they contain help the chicks to grow. In summer their feeding is more varied, adding other herbaceous plants to their diet of conifer seeds: goosefoots and other Compositae.