Eurasian blue tit

TheEurasian blue tit(Cyanistes caeruleus)is a smallpasserinebirdin thetitfamily,Paridae. It is easily recognizable by its blue and yellow plumage and small size.
Eurasian blue tits, usuallyresidentandnon-migratorybirds, are widespread and a common resident breeder throughout temperate and subarcticEuropeand the westernPalearcticin deciduous or mixed woodlands with a high proportion ofoak. They usually nest in tree holes, although they easily adapt to nest boxes where necessary. Their main rival for nests and in the search for food is the larger and more commongreat tit.
The Eurasian blue tit prefers insects and spiders for its diet. Outside the breeding season, they also eat seeds and other vegetable-based foods. The birds are famed for their acrobatic skills, as they can hold on to the outermost branches of trees and shrubs and hang upside down when looking for food.
The Eurasian blue tit was described byCarl Linnaeusin 1758 in the10th editionof hisSystema Naturaeunder thebinomial nameParus caeruleus.Parusis the classical Latin for a tit andcaeruleusis the Latin for dark blue orcerulean.Two centuries earlier, before the introduction of thebinomial nomenclature, the same Latin name had been used by the Swiss naturalistConrad Gesnerwhen he described and illustrated the blue tit in hisHistoriae animaliumof 1555.
In 2005, analysis of themtDNAcytochromebsequencesof the Paridae indicated thatCyanisteswas an early offshoot from the lineage of other tits, and more accurately regarded as a genus rather than a subgenus ofParus.The current genus name,Cyanistes, is from theAncient Greekkuanos, "dark blue".TheAfrican blue tit(Cyanistes teneriffae) was formerly consideredconspecific.
There are currently at least nine recognised subspecies:
tit'(Cyanistes × pleskei) is a commoninterspecific hybridbetween this species and theazure tit(Cyanistes cyanus), in western Russia. Such birds can look like azure, but with less white on the tail and a bit of yellow on the chest or like blue tit but with whiteish bottom.
The Eurasian blue tit is usually 10.5–12 cm (4.1–4.7 in) long with a wingspan of 17.5–20 cm (6.9–7.9 in) for bothsexes, and weighs about 11 g (0.39 oz).A typical blue tit has an intensively 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 theabdomen—the yellowness is indicative of the number of yellowy-greencaterpillarseaten, due to high levels ofcarotenepigmentsin the diet.The bill is black, the legs bluish grey, and the irises dark brown. The sexes are similar and often indistinguishable to human eyes, but under ultraviolet light, males have a brighter blue crown.Juvenile birds are more yellowish and have fewer contrasting colors. They become similar to mature ones in September, although some parts of the wings are kept until May/June next year.
Blue tits can also see inultraviolet light, which is one of the ways they can distinguish whether the bird they're seeing is a male, female or juvenile.A male's cap is more intensively blue than a female's or chick's.
There are currently around 20 to 44 million pairs in Europe.
The Eurasian blue tit and the related hybrids are considered native species in areas of theEuropeancontinent with a mainlytemperateorMediterranean climate, and in parts of theMiddle East. These areas include Ireland, the United Kingdom and most of theEuropean UnionandEFTA(exceptMalta, where they are considered vagrant, andIceland, where they are absent), plus: Albania, Algeria, Andorra, Armenia, Azerbaijan, Belarus, Bosnia and Herzegovina, Georgia, Iran, Iraq, Jordan, Kazakhstan, Lebanon, Libya, Moldova, Montenegro, Morocco, North Macedonia, Russia, San Marino, Serbia, Syria, Tunisia, Turkey, Vatican City and Ukraine.
InGreat Britainthe Eurasian blue tit can be found in a variety of environments, and is typically found in deciduous woodland, parks, gardens and even in the centre of towns.
Eurasian blue andgreat titsform mixed winter flocks, and the former are perhaps the better gymnasts in the slender twigs. A Eurasian blue tit will often ascend a trunk in short jerky hops, reminiscent of atreecreeper. As a rule the bird roosts inivyorevergreens, but in harsh winters will roost wherever there is a suitable small hole, be it in a tree or nesting box. They are very agile and can hang from almost anywhere.
This is a common and popular European garden bird, due to its perky acrobatic performances when feeding on nuts or suet. It swings beneath the holder, calling "tee, tee, tee" or a scolding "churr".
The Eurasian blue tit will nest in any suitable hole in a tree, wall, or stump, or an artificial nest box, often competing withhouse sparrowsor great tits for the site. Few birds more readily accept the shelter of a nesting box; the same hole is returned to year after year, and when one pair dies another takes possession. It is estimated by theRSPBthat there are 3,535,000 breeding pairs in the UK.
During the incubation period, female blue tits perform all of the incubation, however the male feeds the female during this time. During the nestling period, both female nest attendance and male feeding rate are higher in the morning, declining throughout the day.Although socially monogamous, blue tits regularly engage inextra-pair copulationswith other individuals.
Eggs are 14–18 mm (0.55–0.71 in) long and 10.7–13.5 mm (0.42–0.53 in) wide. Egg size appears to depend mostly on the size of individual females and secondarily on habitat, with smaller eggs found at higher altitudes. The clutch's total weight can be 1.5 times as heavy as the female bird.
A study found that the timing of breeding in blue tits is related to the expression of nestlingcarotenoid‐based coloration, which could play a role in offspring–parent communication.
The bird is a close sitter, hissing and biting at an intruding finger. In the southwest of England, such behaviour has earned the Eurasian blue tit the colloquial nickname "Little Billy Biter" or "Billy Biter."When protecting its eggs, it raises its crest, but this is a sign of excitement rather than anger, for it is also elevated during nuptial display. The nesting material is usually moss, wool, hair, and feathers, and the eggs are laid in April or May. The number in the clutch is often very large, but seven or eight eggs are normal. Clutch size varies with latitude and other geographic parameters. Some bigger clutches may be laid by two or even more hens in some locations, but single hen clutches of 14 have been verified in the UK. It is not unusual for a single bird to feed the chicks in the nest at a rate of one feeding every 90 seconds during the height of the breeding season. In winter, they form flocks with other tit species.
In an analysis carried out usingring-recoverydata in Britain, the survival rate for juveniles in their first year was 38%, while the adult annual survival rate was 53%.From these figures the typical lifespan is only three years.Within Britain, the maximum recorded age is 10 years and 3 months for a bird that was ringed inBedfordshire.The maximum recorded age overall is 11 years and 7 months for a bird in the Czech Republic.However,
The Eurasian blue tit feeds on many insects, other small invertebrates and their larvae, though it is fond of young buds and fruits of various trees, especially when insect prey is scarce, and may pull them to bits in the hope of finding insects.It is a well-known predator of manyLepidopteraspecies including theWood Tiger moth. No species, however, destroys more coccids andaphids, the worst foes of many plants. It takes leaf miner grubs and green tortrix moths (Tortricidae). In common with all members of the family, seeds are also eaten.
Eurasian blue tits use songs and calls 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.Communication with other Eurasian blue tits is the most important motivation for the use of calls. They 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 such as thegreat tit, theEuropean robinor thetreecreeper) about the presence of predators in the neighbourhood. Scolding, for example, is used when a ground predator (e.g. fox, cat or dog), a low flying predator or a perched owl are noticed.Sometimes this is followed by mobbing behaviour in which birds gather together in flocks to counter a predator. The alarm-whistle warns other birds about the proximity of aEurasian sparrowhawk, anorthern goshawk, acommon buzzardor other flying predators that form a potential danger in the air. A series of high-pitched 'zeedling' notes are given by both partners before and during copulation.The begging-call is used by juveniles to beg for food from parents.
An interesting example ofculturally transmitted learningin birds was the phenomenon dating from the 1920s of blue tits teaching one another how to open traditional Britishmilk bottleswith foil tops, to get at the cream underneath.Such behaviour has since been gradually suppressed as a result of the declining popularity of both full-fat milk andmilk delivery.In addition, the instinct to strip bark from trees in search of insects has developed into a tendency to peel building materials such asthatch,wallpaper,stuccoand windowputty.
The small size of the Eurasian blue tit makes it vulnerable to prey by larger birds such asjayswho catch the vulnerable fledglings when they leave the nest. The most important predator is probably theEurasian sparrowhawk, closely followed by thedomestic cat. Nests may be robbed by mammals such asweaselsandred squirrels, as well as introducedgrey squirrelsin the UK.
The successful breeding of chicks is dependent on sufficient supply of greencaterpillarsas well as satisfactory weather. Breeding seasons may be affected badly if the weather is cold and wet between May and July, particularly if this coincides with the emergence of thecaterpillarson which the nestlings are fed.
Eurasian blue tits are known to be host to feathermites, and rarelyliceandflat flies. In Europe, the only feather mite species known to live on the blue tit host isProctophyllodes stylifer. However, this mite seems to be of no concern to the bird as, until now, it is only known to feed on dead feather tissue.P. styliferlives all its developmental stages, i.e. egg, larva, protonymph, tritonymph and adult, within the plumage of the same host. The usual sites whereP. styliferis encountered are the remiges and the rectrices of the bird where they can be found tandemly positioned between the barbs of the rachis.
The Eurasian blue tit is classified as aleast concern specieson theIUCN Red List(version 3.1),and as a Green Status species, since 1996, by theRoyal Society for the Protection of Birdsin the United Kingdom.
The Eurasian blue tit has appeared on many stamps and ornaments. Its most recent appearance on a British stamp was the 2010Birds of Britainseries.