20-11-2017 LAKESIDE THURROCK, ESSEX - BRITISH BLUE TIT (Cyanistes caeruleus ssp. obscurus)

                               

The Eurasian blue tit (Cyanistes caeruleus) is a small passerine bird easily recognizable by its blue and yellow plumage. The bird is famed for its acrobatic skills, as it can cling to the outermost branches and hang upside down when looking for food.

A typical Eurasian blue tit has an azure-blue crown and dark blue line passing through the eye, and encircling the white cheeks to the chin, giving the bird a very distinctive appearance. The forehead and a bar on the wing are white. The nape, wings, and tail are blue and the back is yellowish-green. The underparts are mostly sulphur-yellow with a dark line down the abdomen. The bill is black, the legs bluish grey, and the irides dark brown. The sexes are similar, but under ultraviolet light, males have a brighter blue crown. Young blue tits are noticeably more yellow.

Eurasian blue tits are widespread and common resident breeders throughout temperate and subarctic Europe and in parts of the Middle East. They inhabit deciduous or mixed woodlands with a high proportion of oak, shrubland with scattered trees, and hedgerows. These small birds are also common in parks, gardens, and even in the center of towns.

Eurasian blue tits are usually resident and non-migratory birds. They are social and often form mixed winter flocks with Great tits. These small birds are active during the day spending most of their time searching for food in trees, bushes, and sometimes on the ground. Blue tits are very active and agile when foraging; they will often ascend a trunk in short jerky hops, imitating a treecreeper, and can hang from almost anywhere. As a rule, they roost in ivy or evergreens, but in harsh winters will roost wherever there is a suitable small hole, be it in a tree or nesting box. Eurasian blue tits sing and call throughout the year. Songs are mostly used in late winter and spring to defend the territory or to attract mates. Calls are used for multiple reasons. The birds inform one another of their location in trees by means of contact-calls.

They use alarm-calls to warn others (including birds of other species) about the presence of predators in the neighborhood. Scolding, for example, is used when a ground predator (e.g. fox, cat, or dog), a low-flying predator, or a perched owl is noticed. Sometimes this is followed by mobbing behavior in which birds gather together in flocks to counter a predator. The alarm whistle warns other birds about the proximity of a Eurasian sparrowhawk, a northern goshawk, a common buzzard, or other flying predators that form a potential danger in the air.

Eurasian blue tits are polygynous meaning that males mate with more than one female. The breeding season takes place between April and late June. Courtship includes flights performed by the male and both partners then give a series of high-pitched 'zeedling' notes. Eurasian blue tits nest in any suitable hole in a tree, wall, or stump, or an artificial nest box, often competing with house sparrows or great tits for the site. The nest itself is a cup made with dried grasses, moss, leaves, wool, hair, and feathers. The female usually produces 2 broods per year laying 7-14 eggs in each clutch. Incubation lasts about 12 to 16 days and is performed by the female. The male feeds the female during this time. The chicks hatch altricial (helpless) and are fed by both parents. They usually spend 3 weeks in the nest before fledging.