Eurasian blue tit

The Eurasian blue tit (Cyanistes caeruleus)[2] is a small passerine bird in the tit family, Paridae. It is easily recognisable by its blue and yellow plumage and small size.

Eurasian blue tit
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Paridae
Genus: Cyanistes
Species:
C. caeruleus
Binomial name
Cyanistes caeruleus
  Eurasian blue tit range
  African blue tit range
Synonyms

Parus caeruleus Linnaeus, 1758

Eurasian blue tit in Sweden, April 2018

Eurasian blue tits, usually resident and non-migratory birds, are widespread and a common resident breeder throughout temperate and subarctic Europe and the western Palearctic 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 larger and more common 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 acrobatic skills, as they can hold on to the outermost branches of trees and shrubs and hang upside down when looking for food.

Taxonomy

The Eurasian blue tit was described by Carl Linnaeus in 1758 in the 10th edition of his Systema Naturae under the binomial name Parus caeruleus.[3] Parus is the classical Latin for a tit and caeruleus is the Latin for dark blue or cerulean.[4] Two centuries earlier, before the introduction of the binomial nomenclature, the same Latin name had been used by the Swiss naturalist Conrad Gesner when he described and illustrated the blue tit in his Historiae animalium of 1555.[5]

In 2005, analysis of the mtDNA cytochrome b sequences of the Paridae indicated that Cyanistes was an early offshoot from the lineage of other tits, and more accurately regarded as a genus rather than a subgenus of Parus.[6] The current genus name, Cyanistes, is from the Ancient Greek kuanos, "dark blue".[4] The African blue tit (Cyanistes teneriffae) was formerly considered conspecific.

Subspecies

There are currently at least nine recognised subspecies:[7]

  • 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): found in Ireland, Britain and Channel Islands[8]
  • C. c. ogliastrae – (Hartert, 1905): found in Portugal, southern Spain, Corsica and Sardinia
  • C. c. balearicus – (von Jordans, 1913): found on Majorca Island (Balearic Islands)
  • C. c. calamensis – (Parrot, 1908): found in southern Greece, Pelopónnisos, Cyclades, Crete and Rhodes
  • C. c. orientalis – Zarudny & Loudon, 1905: found in southern European Russia (Volga River to central and southern Urals)
  • C. c. satunini – Zarudny, 1908: found in the Crimean Peninsula, Caucasus, Transcaucasia and northwestern Iran to eastern Turkey
  • C. c. raddei – Zarudny, 1908: found in northern Iran
  • C. c. persicus – (Blanford, 1873): found in the Zagros Mountains

Hybrids

Pleske's tit (Cyanistes × pleskei) is a common interspecific 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.[9]

Description

The Eurasian blue tit is usually 12 cm (4.7 in), long with a wingspan of 18 cm (7.1 in) for both sexes, and weighs about 11 g (0.39 oz).[10] 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.[11] The bill is black, the legs bluish grey, and the irides dark brown. The sexes are similar and often indistinguishable to human eyes, but under ultraviolet light, males have a brighter blue crown.[12] Young blue tits are noticeably more yellow.

Distribution and habitat
Reported range from observations reported to eBird
  Year-Round Range
  Summer Range
  Winter Range
Blue tit displaying aggression during ringing

There are currently around 20–44 million pairs in Europe.[13]

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 Ireland, 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, 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.[14]

In Great Britain the 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.[15]

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, reminiscent of a treecreeper. As a rule the bird roosts 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. 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.[13]

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.[16]

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.[17]

Juvenile in Pimlico, London

A study found that the timing of breeding in blue tits is related to the expression of nestling carotenoid‐based coloration, which could play a role in offspring–parent communication.[18]

The bird is a close sitter, hissing and biting at an intruding finger. In the South West of England such behaviour has earned the Eurasian blue tit the colloquial nickname "Little Billy Biter" or "Billy Biter", originating from the UK.[19] 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, 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 feed every 90 seconds during the height of the breeding season. In winter they form flocks with other tit species.

In an analysis carried out using ring-recovery data in Britain, the survival rate for juveniles in their first year was 38%, while the adult annual survival rate was 53%.[20] From these figures the typical lifespan is only three years.[10] Within Britain, the maximum recorded age is 10 years and 3 months for a bird that was ringed in Bedfordshire.[21] The maximum recorded age overall is 11 years and 7 months for a bird in the Czech Republic.[22]

Diet
Eurasian blue tit eating peanuts from a string, Italy

The Eurasian blue tit feeds on many insects, though it is fond of young buds 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 many Lepidoptera species including the Wood Tiger moth. No species, however, destroys more coccids and aphids, 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.

Voice

Eurasian blue tits use songs and calls throughout the year.[23] Songs are mostly used in late winter and spring to defend the territory or to attract mates. Calls are used for multiple reasons.[24] 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.[25] 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.[26] The begging-call is used by juveniles to beg for food from parents.

Learnt behaviours

An interesting example of culturally transmitted learning in birds was the phenomenon dating from the 1920s of blue tits teaching one another how to open traditional British milk bottles with foil tops, to get at the cream underneath[27] 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 in plastic containers with hard plastic lids, instead of the milkman).[28] In addition, the instinct to strip bark from trees in search of insects has developed into a tendency to peel building materials such as thatch, wallpaper, stucco and window putty.[29]

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 they leave the nest. The most important predator is probably the sparrowhawk, closely followed by the domestic cat. Nests may be robbed by mammals such as weasels and red squirrels, as well as introduced 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.[30]

Parasites
A bald blue tit with mite

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. 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. 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.[31]

Status and conservation

The Eurasian blue tit is classified as a least concern species on the IUCN Red List (version 3.1),[1] and as a Green Status species, since 1996, by the Royal Society for the Protection of Birds in the United Kingdom.[10][13]

Cultural significance

The Eurasian blue tit has appeared on many stamps and ornaments. Its most recent appearance on a British stamp was the 2010 Birds of Britain series.[32]

References
  1. BirdLife International (2017). "Cyanistes caeruleus". IUCN Red List of Threatened Species. 2017: e.T103761667A118689415. doi:10.2305/IUCN.UK.2017-3.RLTS.T103761667A118689415.en. Retrieved 12 November 2021.
  2. Gill, Frank; Wright, Minturn (2006). Birds of the World: Recommended English Names (1st ed.). Princeton University Press. pp. ix, 259. ISBN 978-0-691-12827-6.
  3. Linnaeus, C. (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata (in Latin). Vol. v.1. Holmiae. [Stockholm]: (Laurentii Salvii). p. 190. P. remigibus caerulescentibus : primoribus margine exteriore albis, fronte alba, vertice caeruleo.
  4. Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 83, 293. ISBN 978-1-4081-2501-4.
  5. Gesner, Conrad (1555). Historiæ animalium liber III qui est de auium natura. Adiecti sunt ab initio indices alphabetici decem super nominibus auium in totidem linguis diuersis: & ante illos enumeratio auium eo ordiné quo in hoc volumine continentur (in Latin). Zurich: Froschauer. p. 616. NB –The link is to the preceding page.
  6. Gill, Frank B.; Slikas, Beth; Sheldon, Frederick H. (2005). "Phylogeny of titmice (Paridae): II. Species relationships based on sequences of the mitochondrial cytochrome-b gene". Auk. 122 (1): 121–143. doi:10.1642/0004-8038(2005)122[0121:POTPIS]2.0.CO;2.
  7. Clements, James (2011). The Clements Checklist of Birds of the World (6th ed.). Cornell University Press. ISBN 978-0-7136-8695-1.
  8. Mlíkovský, Jiří (26 August 2011). "Nomenclatural and taxonomic status of bird taxa (Aves) described by an ornithological swindler, Josef Prokop Pražák (1870–1904)". Zootaxa. 3005 (3005): 45–68. doi:10.11646/zootaxa.3005.1.2.
  9. Harrap, Simon; Quinn, David (Illus.) (2010). Tits, Nuthatches and Treecreepers. A&C Black. p. 94. ISBN 978-1-4081-3458-0.
  10. Robinson, R.A. (8 December 2010). "Blue Tit (Cyanistes caeruleus)". BirdFacts: profiles of birds occurring in Britain & Ireland (BTO Research Report 407). Thetford: British Trust for Ornithology. Retrieved 23 August 2011.
  11. "Blue tit, Nature Wildlife". BBC. 23 August 2011. Retrieved 23 August 2011.
  12. Hunt, S.; Bennett, A.T.D.; Cuthill, I.C.; Griffiths, R. (22 March 1998). "Blue tits are ultraviolet tits". Proceedings of the Royal Society B: Biological Sciences. Royal Society. 265 (1395): 451–455. doi:10.1098/rspb.1998.0316. PMC 1688906.
  13. "Blue Tit". RSPB. 23 August 2011. Retrieved 23 August 2011.
  14. "Parus caeruleus (Blue Tit) – Map". IUCN Red List of Threatened Species. International Union for Conservation of Nature. Retrieved 1 May 2014.
  15. Holden, Peter (2012). RSPB Handbook Of British Birds. p. 262. ISBN 978-1-4081-2735-3.
  16. Bambini, G.; Schlicht, E.; Kempenaers, B. (2019). "Patterns of female nest attendance and male feeding throughout the incubation period in Blue Tits Cyanistes caeruleus". Ibis. 161 (2): 50–65. doi:10.1111/ibi.12614.
  17. Bauer, Kurt M.; Glutz von Blotzheim, Urs Noel, eds. (1993). "P. c. caeruleus". Handbuch der Vögel Mitteleuropas [Handbook of the Birds of Central Europe] (in German). Vol. 13/I. Aula. pp. 581–587.
  18. Janas, Katarzyna; Lutyk, Dorota; Sudyka, Joanna; Dubiec, Anna; Gustafsson, Lars; Cichoń, Mariusz; Drobniak, Szymon (2020). "Carotenoid-based coloration correlates with the hatching date of Blue Tit Cyanistes caeruleus nestlings". Ibis. 162 (3): 645–654. doi:10.1111/ibi.12751. ISSN 1474-919X. S2CID 182116803.
  19. Stenning, Martyn (22 February 2018). The Blue Tit. Bloomsbury Publishing. ISBN 9781472937391 – via Google Books.
  20. Siriwardena, G.M.; Baillie, S.R.; Wilson, J.D. (1998). "Variation in the survival rates of some British passerines with respect to their population trends on farmland". Bird Study. 45 (3): 1998. doi:10.1080/00063659809461099.
  21. Robinson, R.A.; Leech, D.I.; Clark, J.A. "Longevity records for Britain & Ireland in 2014". British Trust for Ornithology. Archived from the original on 7 April 2017. Retrieved 26 March 2016.
  22. Fransson, T.; Kolehmainen, T.; Kroon, C.; Jansson, L.; Wenninger, T. (2010). "EURING list of longevity records for European birds". European Union for Bird Ringing (EURING). Retrieved 26 March 2016.
  23. Cramp, S.; Perrins, C.M.P., eds. (1993). Handbook of the Birds of Europe the Middle East and North Africa: The Birds of the Western Palearctic. Vol. VII. Oxford, New York: Oxford University Press. ISBN 978-0-19-854679-5.
  24. Bijnens, L.; Dhondt, A.A. (1984). "Vocalizations in a Belgian Blue Tit Parus c. caeruleus population". Le Gerfaut. 74: 243–269.
  25. Klump, G.M.; Curio, E. (1983). "Reactions of Eurasian Blue Tits Parus caeruleus to Hawk Models of Different Sizes". Bird Behavior. 4 (2): 78–81.
  26. Hinde, R.A. (1952). "The behaviour of the Great Tit (Parus Major) and some other related species". Behaviour. Supplement (2): 1–201. JSTOR 30039125.
  27. Sasvári, Lajos (August 1979). "Observational learning in great, blue and marsh tits". Animal Behaviour. 27 (3): 767–771. doi:10.1016/0003-3472(79)90012-5. S2CID 53150665.
  28. McCarthy, Michael (31 December 2003). "Blue tits lose their bottle as milk thieves". The Independent. Retrieved 22 August 2011.
  29. Information, Reed Business (24 October 1952). "Birds take a fancy to putty". New Scientist. 2 (49): 8. Retrieved 6 May 2016.
  30. McCambridge, Hazel (17 July 2019). "A Blue Tit diary". British Trust for Ornithology. Retrieved 26 May 2020.
  31. Atyeo, Warren T.; Braasch, Norman L. (1966). The feather mite genus 'Proctophyllodes (Sarcoptiformes: Proctophyllodidae) (1st ed.). University of Nebraska. pp. 1–351.
  32. Stephens, Kate (2010), Birds of Britain I – A Presentation Pack, Royal Mail
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