Long-tailed tit

Long-tailed tit
Perched on a washing line in Shropshire
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Aegithalidae
Genus: Aegithalos
Species: A. caudatus
Binomial name
Aegithalos caudatus
(Linnaeus, 1758)

The long-tailed tit or long-tailed bushtit (Aegithalos caudatus) is a common bird found throughout Europe and Asia. The genus name Aegithalos was a term used by Aristotle for some European tits, including the long-tailed tit. The specific caudatus is Latin and is derived from cauda, "tail".[2]

Taxonomy and systematics

The long-tailed tit was first classified as a true tit of the Parus group. Parus has since been split from the Aegithalidae, with the latter becoming a distinct family containing three genera:

This is the only representative of the Aegithalidae in northern Eurasia.[3] The long-tailed tit exhibits complex global variation with 19 races recognised, divisible into three groups:[4]

The silver-throated bushtit was formerly considered conspecific.

Where the groups meet there are extensive areas occupied by very variable ‘hybrids’. The British long-tailed tit, subspecies rosaceus, belongs to the europaeus group. Biochemical evidence has shown Aegithalidae to be closely related to the babblers.[3]

Description

This species has been described as a tiny (at only 13–15 cm in length, including its 7–9 cm tail), round-bodied tit with a short, stubby bill and a very long, narrow tail.[4] The sexes look the same and young birds undergo a complete moult to adult plumage before the first winter. The plumage is mainly black and white, with variable amounts of grey and pink.[4]

Distribution and habitat

The long-tailed tit is globally widespread throughout temperate northern Europe and Asia, into boreal Scandinavia and south into the Mediterranean zone.[3] It inhabits deciduous and mixed woodland with a well-developed shrub layer, favouring edge habitats. It can also be found in scrub, heathland with scattered trees, bushes and hedges, in farmland and riverine woodland,[4] parks and gardens. The bird's year-round diet of insects and social foraging bias habitat choice in winter towards deciduous woodland, typically of oak, ash and locally sycamore species. For nesting, strong preference is shown towards scrub areas.[3] The nest is usually built in thorny bushes less than 3 metres above the ground.[4]

Behaviour and ecology

Food and feeding

The long-tailed tit is insectivorous throughout the year. It eats predominantly arthropods, preferring the eggs and larvae of moths and butterflies. Occasional vegetable matter is taken in the autumn.[3]

Nest

A long-tailed tit in its nest.
Egg, Collection Museum Wiesbaden

The nest of the long-tailed tit is constructed from four materials - lichen, feathers, spider egg cocoons and moss, with over 6,000 pieces used for a typical nest. The nest is a flexible sac with a small, round entrance on top, suspended either low in a gorse or bramble bush or high up in the forks of tree branches. The structural stability of the nest is provided by a mesh of moss and spider silk. The tiny leaves of the moss act as hooks and the spider silk of egg cocoons provides the loops; thus forming a natural form of velcro.[5] The tit lines the outside with hundreds of flakes of pale lichens - this provides camouflage. Inside, it lines the nest with more than 2,000 downy feathers to insulate the nest.[5] Nests suffer a high rate of predation with only 17% success.[6]

Social behaviour

Extensive work has been done by at Wytham Wood, Oxfordshire, in Germany and Japan.

Outside the breeding season they form compact flocks of 3 to 30 birds, composed of family parties (parents and offspring) from the previous breeding season, together with any extra adults that helped to raise a brood.[3] These flocks will occupy and defend territories against neighbouring flocks.[7] The driving force behind the flocking behaviour is thought to be that of winter roosting, being susceptible to cold; huddling increases survival through cold nights.[8]

From July to February, the non-breeding season, long-tailed tits form flocks of relatives and non-relatives, roosting communally. When the breeding season begins, the flocks break up, and the birds attempt to breed in monogamous pairs.[9] Males remain within the winter territory, while females have a tendency to wander to neighbouring territories.[7]

Pairs whose nests fail have three choices: try again, abandon nesting for the season or help at a neighbouring nest. It has been shown that failed pairs split and help at the nests of male relatives,[8][10][11] recognition being established vocally.[10] The helped nests have greater success due to higher provisioning rates and better nest defence.[8] At the end of the breeding season, in June–July, the birds reform the winter flocks in their winter territory.[7]

Long-tailed tits resting, mid-afternoon in energy saving anti-parallel paired formation in a willow

Helpers

Due to high predation, there is a high nest failure rate. If nest failure occurs after the beginning of May, failed breeders will not try to re-nest, but may become helpers at a nest of another, usually related, pair. In one study, around 50% of nests had one or more helpers. By helping close relatives, helpers gain indirect fitness benefits by increasing the survivability of related offspring. Helpers may also gain greater access to mates and territories in the future. Helpers also gain experience raising young and therefore their future offspring have greater survivability rates.

Males and females are equally likely to become helpers. Parents may allow the care of helpers to be additive to their own efforts, or on the other extreme, they may reduce their efforts with the care of the helpers. Juvenile males have a higher survivability than juvenile females, although the survival rate for adults of the two sexes is the same. Offspring that were raised with helpers have a higher survivability than offspring raised without. Failed breeders that became helpers have a higher survivability than failed breeders who did not. This may be because of the reduced energy expenditure from sharing a nest. This is similar to acorn woodpeckers and green wood hoopoes. However, failed breeders that did not help are more likely to breed successfully in subsequent years, so there may be a cost of helping. This may be due to helpers having relatively poorer body conditions at the end of the breeding season, similar to pied kingfisher and white-winged chough. Successful breeders have a survivability rate around the survivability of failed breeders who became helpers.[9]

Voice

Vocalisations are a valuable aid to locating and identifying these birds. When in flocks they issue constant contact calls and are often heard before they are seen. They have three main calls, a single high pitched ‘pit’, a ‘triple trill’ eez-eez-eez, and a rattling ‘schnuur’. The calls become faster and louder when the birds cross open ground or if an individual becomes separated from the group.[12]

Status and conservation

Globally, common throughout its range, only becoming scarce at the edge of the distribution.[4] The IUCN, BirdLife International and The British Trust for Ornithology (BTO) all list the long-tailed tit as a ‘species of least concern’, currently under little or no threat and is reasonably abundant.[13][14] Due to their small size they are vulnerable to extreme cold weather with population losses of up to 80% being recorded in times of prolonged cold. It is thought that populations rapidly return to previous levels due to high breeding potential[4]

References

  1. ↑ BirdLife International (2014). "Aegithalos caudatus". IUCN Red List of Threatened Species. Version 2014.2. International Union for Conservation of Nature. Retrieved 29 August 2014.
  2. ↑ Jobling, James A (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 33, 94. ISBN 978-1-4081-2501-4.
  3. 1 2 3 4 5 6 Cramp, S. and Perrins, C. (1993) Handbook of the birds of Europe, the Middle East and North Africa: the birds of the Western Palearctic: Flycatchers to Shrikes. Volume 8. Oxford, Oxford University Press.
  4. 1 2 3 4 5 6 7 8 Harrap, S. and Quinn, D. (1996) Helm Identification Guides: Tits, Nuthatches & Treecreepers. Helm Identification Guides.1 ed. London, Christopher Helm (A&C Black)
  5. 1 2 Hansell, Michael Henry (2007). Built by animals: the natural history of animal architecture. Oxford University Press. pp. 76, 77. ISBN 978-0-19-920556-1. Retrieved 1 July 2011.
  6. ↑ Hatchwell, B. J., et al. (1999) Reproductive success and nest-site selection in a cooperative breeder: effect of experience and a direct benefit of helping. The Auk, 116(2), pp.355-363
  7. 1 2 3 Gaston, A. J. (1973) The ecology and behaviour of the Long-tailed Tit. Ibis, 115(3), pp.330-351
  8. 1 2 3 Glen, N. W. and Perrins, C. M. (1988) Cooperative breeding by long-tailed tits. British Birds, 81(12), pp.630-641
  9. 1 2 Mcgowan, Andrew; Ben J. Hatchwell & Richard J. W. Woodburn (2003). "The Effect of Helping Behaviour on the Survival of Juvenile and Adult Long-tailed Tits Aegithalos Caudatus". Journal of Animal Ecology. 72 (3): 491–99. doi:10.1046/j.1365-2656.2003.00719.x.
  10. 1 2 Hatchwell, J., et al. (2001) Kin discrimination in cooperatively breeding long-tailed tits. Proceedings of the Royal Society of London - B, 268(1470), pp.885-890
  11. ↑ Sharp, S. P., Simeoni, M. and Hatchwell, B. (2008) Dispersal of sibling coalitions promotes helping among immigrants in a cooperatively breeding bird. Proceedings of the Royal Society Biological Sciences Series B, 275(1647), pp.2125-2130
  12. ↑ Gaston, A. J. (1973) The ecology and behaviour of the Long-tailed Tit. Ibis, 115(3), pp.330-351.
  13. ↑ Bird, J. and Butchart, S. B. I. (BirdLife International 2009) Aegithalos caudatus (Long-tailed Tit, Long-tailed Bushtit) [Internet]. Available from: <http://www.iucnredlist.org/apps/redlist/details/147903/0> [Accessed 29 November 2009]
  14. ↑ Robinson, R. A. (2005) BTO BirdFacts - long-tailed tit [Internet]. Available from: <http://blx1.bto.org/birdfacts/results/bob14370.htm> [Accessed 27/11/2009]
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