Eurasian Blue Tit - Cyanistes caeruleus

[OldGreenVulture]

Eurasian Blue Tit - Cyanistes caeruleus.



Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Paridae
Genus: Cyanistes
Species: C. caeruleus

The Eurasian Blue Tit (Cyanistes caeruleus or Parus caeruleus) is a small passerine bird in the tit family Paridae. The bird is easily recognisable by its blue and yellow plumage, but various authorities dispute their scientific classification.

Eurasian Blue Tits, usually resident and non-migratory birds, are widespread and a common resident breeder throughout temperate and subarctic Europe and western Asia in deciduous or mixed woodlands with a high proportion of oak. 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 much larger Great 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 skill, as they can cling to the outermost branches and hang upside down when looking for food.

Description
The Eurasian Blue Tit is usually 12 centimetres (4.7 in) long with a wingspan of 18 centimetres (7.1 in) for all genders, and weighs about 11 grams (0.39 oz).

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 is mostly sulphur-yellow with a dark line down the abdomen - the yellowness is indicative of the number of yellowy-green caterpillars eaten, due to high levels of carotene pigments in the diet. 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.



Distribution and habitat
There are currently around 20–44 million pairs in Europe.

The Eurasian Blue Tit and the related hybrids are considered native species in areas of the European continent with a mainly temperate or Mediterranean climate, and in parts of the Middle East. These areas include the United Kingdom and most of the European Union and EFTA (except Malta, where they are considered vagrant, and Iceland, where they are absent), plus: Albania, Andorra, Armenia, Azerbaijan, Belarus, Bosnia and Herzegovina, Georgia, Iran, Iraq, Jordan, Kazakhstan, Lebanon, the Republic of Macedonia, Moldova, Montenegro, Russia, San Marino, Serbia, Syria, Turkey, Vatican City and Ukraine.


Eurasian Blue Tit range dark green, African Blue Tit range light green.

Taxonomy
This species was first described by Linnaeus in his Systema naturae in 1758 as Parus caeruleus.

Most authorities retain Cyanistes as a subgenus of Parus, but the British Ornithologists' Union treats Cyanistes as a distinct genus. This is supported by mtDNA cytochrome b sequence analysis which suggests that Cyanistes is not only distinct, but not close to other tits. The African Blue Tit was formerly considered conspecific.

Subspecies
There are currently at least nine recognised subspecies:

C. c. caeruleus (Linnaeus, 1758), the nominate subspecies, occurring in Continental Europe to northern Spain, Sicily, northern Turkey and northern Urals
C. c. obscurus (Pražák, 1894), Ireland, Britain and Channel Islands
C. c. ogilastrae (Hartert, 1905), Portugal, southern Spain, Corsica and Sardinia
C. c. balearicus (von Jordans, 1913), Majorca Island (Balearic Islands)
C. c. calamensis (Parrot, 1908), southern Greece, Pelopónnisos, Cyclades, Crete and Rhodes
C. c. orientalis (Zarudny & Loudon, 1905), southern European Russia (Volga River to central and southern Urals)
C. c. satunini (Zarudny, 1908), Crimean Peninsula, Caucasus, Transcaucasia and northwestern Iran to eastern Turkey
C. c. raddei (Zarudny, 1908), northern Iran
C. c. persicus (Blanford, 1873), Zagros Mountains

Hybrids
Pleske's Tit (Cyanistes pleskei) is a common hybrid between this species and the Azure Tit (Cyanistes cyanus) in western Russia. The cap is usually darker than the Azure Tit, and the tail is paler than the Eurasian Blue Tit.

Behaviour and ecology
Eurasian Blue and Great Tits form 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, imitating a Treecreeper. As a rule the bird roosts in ivy or evergreens, but in harsh winters will nest 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".

Breeding
The Eurasian Blue Tit will 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. 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 the RSPB that there are 3,535,000 breeding pairs in the UK.

The bird is a close sitter, hissing and biting at an intruding finger. 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 are normal, and bigger clutches are usually laid by two or even more hens. It is not unusual for a single bird to feed the chicks in the nest at a rate of one feed every ninety (90) seconds during the height of the breeding season. In winter they form flocks with other tit species.

Diet
The Eurasian Blue Tit is a valuable destroyer of pests, though it has not an entirely clean sheet as a beneficial species. It is fond of young buds of various trees, and may pull them to bits in the hope of finding insects. No species, however, destroys more coccids and aphids, the worst foes of many plants. It takes leaf miner grubs and green tortrix moths (Tortricidae). Seeds are eaten, as with all this family.

Voice
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 on their location in trees by means of contact-calls. They use alarm-calls to warn others (including birds of other species such as the Great Tit, the European Robin or the Treecreeper) 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 a Eurasian Sparrowhawk, a Northern Goshawk, a Common Buzzard or 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.

Learning
Eurasian Blue Tits are able to culturally transmit learning to other Tit species. An example of this, dating from the 1920s, is the ability to open milk bottles with foil tops, to get at the cream underneath. Such behaviour has been suppressed recently by the gradual change of human dietary habits (low-fat or skimmed milk instead of full-fat), and the way of getting them (from a supermarket, instead of the milkman).

Predators and natural threats
The small size of the Eurasian Blue Tit makes it vulnerable to prey by larger birds such as Jays who catch the vulnerable fledglings when leaving the nest. The most important predator is probably the Eurasian Sparrowhawk, closely followed by the domestic cat. Nests may be robbed by mammals such as weasels and Red Squirrels and Grey Squirrels in the UK.

The successful breeding of chicks is dependent on sufficient supply of green caterpillars as 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 the caterpillars on which the nestlings are fed.

Parasites and lifespan
Eurasian Blue Tits are known to be host to feather mites, and rarely lice and flat flies. In Europe the only feather mite species known to live on the Blue Tit host is Proctophyllodes stylifer. P. stylifer however seems to be of no concern to the bird as, until now, it is only known to feed on dead feather tissue. P. stylifer lives all its developmental stages, i.e. egg, larva, protonymph, tritonymph and adult, within the plumage of the same host. The usual sites where P. stylifer is 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 has an average life expectancy of one-and-a-half to three years. The longest recorded lifespans by country for the species are: 11 years 7 months in the Czech Republic, and 9 years 9 months 2 days in the United Kingdom.

Status and conversation
The Eurasian Blue Tit is classified as a Least Concern species on the IUCN Red List (version 3.1), and as a Green Status species, since 1996, by the Royal Society for the Protection of Birds in the United Kingdom.

From Carnivora

carnivora.net/-t2454.html?

[Eaglehawk]

Social networks reveal dating in blue tits

by Max Planck Society


Blue tits, that often foraged together during winter, were more likely to end up as breeding pairs or as extra-pair partners in spring. Credit: Kristina Beck

Winter associations predict social and extra-pair mating patterns in blue tits. Researchers of the Max Planck Institutes for Ornithology in Seewiesen and for Animal Behavior in Radolfzell show in their new study that blue tits that often foraged together during winter were more likely to end up as breeding pairs or as extra-pair partners, whereby bonds between future breeding partners seem to establish earlier in winter than those between future extra-pair partners.
Many socially monogamous bird species engage in sexual behaviour outside their pair bond, often resulting in extra-pair young. However, despite decades of research, the ability to explain who will have extra-pair young with whom is limited. Researchers of the Max Planck Institute for Ornithology and the Max Planck Institute of Animal Behavior now examined whether social associations prior to the breeding season influenced patterns of social and extra-pair mating. They studied blue tits that typically form socially monogamous pairs, but frequently engage in extra-pair mating. About half of all nests contain at least one young with a genetic father other than the social one, and up to 15 percent of all offspring are sired by extra-pair males. During winter, blue tits forage in large mixed-species flocks where they potentially already meet future mating partners.
The researchers quantified the birds' social associations during foraging events at local bird feeders and while visiting nest-boxes during winter. To obtain these data, they installed a self-designed, custom-built automated monitoring system including 20 feeders and 277 nest-boxes in their forest study site in southern Germany. Blue tits in the study area carried a tiny "Passive Integrated Transponder" (PIT-tag) with an individual code activated externally by the scanning device in the feeder or nest-box. With this setup, the researchers could record the date, time, and identity of every PIT-tagged blue tit visiting. Using these data the researchers created a social network that visualizes who hangs out with whom and how often. They found that 39 percent of the birds present in the study site in winter bred in the subsequent spring. Nearly all social breeding pairs were formed by the individuals present during winter and those that foraged more often together were also more likely to end up as breeding pairs.

Most extra-pair sires are close neighbours

The social network analysis further shows that individuals that are more strongly associated during winter tend to nest closer together. "As most extra-pair sires are close neighbours, one could think that extra-pair paternity in blue tits might simply be the result of coincidental meetings between neighbours, and not a social preference for specific mating partners," says Kristina Beck, first-author of the study. However, the analysis shows that mating patterns can be explained by the strong social association itself: males and females foraging together and those that co-inspected nest-boxes were more likely to have extra-pair young together in the subsequent breeding season.
The researchers also found temporal changes in the social network: social bonds between future breeding partners seem to be established earlier in winter than those between future extra-pair partners. Bart Kempenaers, leading the study, adds: "When and how individuals make mating decisions is still largely unknown. However, our research provides new insights into the dynamics of different types of social relationships. Our work shows that extra-pair mating often happens between individuals that already know each other."

phys.org/news/2020-02-social-networks-reveal-dating-blue.html

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Journal Reference:
Kristina B. Beck et al, Winter associations predict social and extra-pair mating patterns in a wild songbird, Proceedings of the Royal Society B: Biological Sciences (2020). DOI: 10.1098/rspb.2019.2606

Abstract
Despite decades of research, our understanding of the underlying causes of within-population variation in patterns of extra-pair paternity (EPP) remains limited. Previous studies have shown that extra-pair mating decisions are linked to both individual traits and ecological factors. Here, we examine whether social associations among individuals prior to breeding also shape mating patterns, specifically the occurrence of EPP, in a small songbird, the blue tit. We test whether associations during the non-breeding period predict (1) future social pairs, (2) breeding proximity (i.e. the distance between breeding individuals) and (3) the likelihood that individuals have extra-pair young together. Individuals that were more strongly associated (those that foraged more often together) during winter tended to nest closer together. This, by itself, predicts EPP patterns, because most extra-pair sires are close neighbours. However, even after controlling for spatial effects, female–male dyads with stronger social associations prior to breeding were more likely to have extra-pair young. Our findings reveal a carry-over from social associations into future mating decisions. Quantifying the long-term social environment of individuals and studying its dynamics is a promising approach to enhance our understanding of the process of (extra-)pair formation.

royalsocietypublishing.org/doi/10.1098/rspb.2019.2606