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Great Tit Monograph
'The Great tit is perhaps the most-studied small bird in the world' R.H. McCleery and C. M. Perrins (1988)
Introduction
The aim of this web page is to give a few interesting facts and details relating to Great tits within the UK. Although very common within the UK they are a fascinating species to study. The are a number of excellent publications (e.g. [2] and [3]) available which go into far more depth than is applicable here.
The Great tit, Parus major, is a passerine bird in the tit family Paridae [1]. It is the largest of the British tits and is a familiar garden visitor [2],[3],[4],[5]. It is slightly smaller in size than a house sparrow and is a widespread and common species throughout Europe and Asia ranging from Ireland to Japan in any sort of woodland. There are ca. 2 million breeding pairs in Britain and Ireland [6]. Within Europe there are ca. 42 million breeding Great tits.
There are many races of this widespread species but they generally fall into three broad plumage groups:-
Within the UK, Great tits are generally easy to identify. The crown, nape and throat are black. The cheeks are white. The breast and belly are yellow with a black stripe down the centre. There is a white wing bar across the blue-grey wings. The back is olive green and the rump is blue-grey. Legs are grey-blue and the bill is black.
The Great tit is the only British tit in which the sexes can be distinguished in the field with reasonable certainty by plumage differences. The female not only shows less gloss on the black parts than the adult male, but the black stripe down the breast is narrower and does not extend outwards to the legs. The male is also sometimes slightly larger than the female.
Juveniles, before their moult in August/September are paler in colour than adults and their cheek patches are yellow[7]. They also have dusty looking, sooty caps and central bands. A first winter bird in the hand can be distinguished from an older bird by the fact that the fringes to the primary wing coverts are duller than those of the greater coverts, and the centre feather of the bastard wing is edged with green instead of blue/grey.
Voice
Bill Oddie commented that '…if you hear a call and you don't recognise it – it's a Great tit'[8]. Great tits have a wide range of loud calls [9] where an average male might have 32 distinct utterances [3]. A sharp, loud ‘tink tink’ is often produced but perhaps the best known is the repetitive 'tea-cher tea-cher song [10] which sounds very much like a squeeky wheelbarrow, or someone sawing a plank of wood, and can often be heard all year round.
Feeding
Depending on the time of year, Great tits feed on insects such as caterpillars and spiders, seeds like beech mast, and berries. During summer, Great tits tend to feed mainly on invertebrates taken from leaves but in autumn the diet slowly changes to incorporate more seeds and fruits. By November, seeds make up a large proportion of the diet and in periods of low food availability Great tits will enter gardens and feed on peanuts and other food provided by humans. Because of their larger size, Great tits tend to feed on the ground more than other smaller tit species.
Reproduction
The Great tit breeding cycle usually commences in April and is timed so that the period of the eventual broods greatest demand for food coincides with the peak abundance of caterpillars such as those of the Winter Moth (Operophtera brumata). In oak woodland, for example, caterpillar abundance and size increases rapidly in a short pulse after the buds of the leaves on which they feed burst in the Spring. For a while, caterpillars may be superabundant but the glut does not last for long. Since the tree depends on its leaves for photosynthesis it must combat the depredations of the insects in some way. This achieved to some extent by reducing the time over which its developing leaves are palatable to defoliating caterpillars. It does this by reducing their water and protein content and increasing the concentration in them of toxic secondary substances, such as tannins, shortly after the leaf is formed[11]. This means that the caterpillars must time their own hatching to coincide as closely as possible with the leaf-bud burst, and to grow to pupation as quickly as possible, and Great tits must try to time their own breeding to coincide with this pulse of caterpillar biomass [3].
The nest is built by both parents where the nest foundation is typically moss (ca. 5 cm deep) pressed flat by the rubbing action of the female's belly. The moss foundation is usually topped and lined with hair or fur, but rarely feathers as is the case with the Blue tit. The male takes no part in nest building although he may accompany her when she is collecting material.
The female roosts on the nest during the laying period. Although she is in partial contact with the eggs, they do not receive enough heat from her to start their development. The daily egg is laid early in the morning. The eggs are the largest of the British Tits measuring ca. 18 mm by 14 mm with a mass of between 1.3 and 2.3 g. This is often more than 10% of the female's bodyweight so that a full clutch of 4-12 eggs may weigh more than she does [3]. Each egg is smooth, glossy and white with a variable scattering of red/brown spots. After laying, the female usually covers the eggs with nest lining but uncovers them when she returns to the nest in the evening to roost overnight. A few days before the last egg is laid, her brood patch is fully developed. This is a bare area of belly that becomes inflamed with blood vessels and is hot to the touch [3]. In late April to early May, the female incubates her clutch of 5-11 eggs for 13-14 days. During this time the male often feeds the female.
A newly hatched chick has a mass of ca. 1.3 g. During the 18-21 days the chicks are in the nest they increase in mass some 8-10 times and fledge at ca. 16-22 g [3]. During this period the parents may deliver more than 10,000 caterpillars to the brood. Over the whole nesting period, this is equivalent to a total flight distance of at least 100 km (i.e. approximately flying from London to Brighton) for both the male and female Great tit. Work undertaken during the 1950s showed that during the 3 weeks between hatching and fledging each Great tit nestling receives on average ca. 64 g of food. For a brood of 10 chicks this equates to a staggering 640 g. For the parents this is equivalent to delivering 17 times their own body weight of food to the brood over a 3 week period. In human terms this would be something like an adult couple bringing home 103 kg (227 lb) of shopping every day for 3 weeks!
Great tits make excellent parents. Apart from the huge number of caterpillars and spiders the parents bring to the brood they also provide fine grit for the chicks' tiny gizzards and snail shell to provide additional calcium. As well as delivering food the parents also remove the obvious waste products. The chicks produce their faeces in neat gelatinous sacs, each ca. 1 g in mass. After feeding the brood, the parent typically waits for a chick to produce a faecal sac, removes it and takes it far from the nest so as not to betray the nests position to predators.
The parent Great tits are mainly responsible for deciding when the brood fledges. During the last few days of the nestling stage they encourage the chicks to fledge by; reducing the amount of food that they deliver to the chicks so that the brood is forced to fledge largely through hunger; feeding chicks through the nest hole; removing fewer faecal sacs therefore the nest becomes more soiled; and by the female roosting away from the nest.
Consequently, there is a gradual reduction of contact between the parents and brood towards the latter stages of nestling development. Fledging normally occurs early in the morning which gives the family time to familiarise themselves a little with their new surroundings while it is still light. Once fledged the chicks are still dependent on their parents for a week or two. Very occasionally there may be two broods in a season depending on the available food supply.
Behavior
Great tits live in family groups for a short time after breeding, and then join mixed flocks of other species in the late summer and through to spring. Over the Winter period the male and female Great tits pair-up ready for breeding the following year.
Lifespan
Barnes [2] has reported that the maximum age to which a Great tit lives is between 5.5-10 years with a mean of 7.8 years.
Conservation
Great tits are included in the Birds of Conservation Concern Green List (low conservation concern) [12] and are not considered to be globally threatened. Generally, Great tits are are doing well within the UK, both expanding in range and increasing in abundance. This may be a result of milder winters and using nest boxes and feeders in gardens.
[1] National Biodiversity Network Species Dictionary (January 2004): http://www.nhm.ac.uk/nbn [2] Barnes, J. A. G. (1975) The Titmice of the British Isles, David & Charles Holdings, Ltd., NewtonAbbot, UK. [3] Gosler, A. The Great Tit, Hamlyn Species Guide, Hamlyn Ltd., 1993. [4] Lack. P. (1986) The Atlas of wintering birds in Britain and Ireland. T & A D Poyser Ltd, London. [5] Holden, P. & Sharrock, J.T.R. (2002) The RSPB Guide to British Birds. Pan Macmillan, London. [6] http://www.bto.org/ [7] Mullarney, K., Svensson, L., Zetterström, D. & Grant, P.J. (1999) Collins Bird Guide. HarperCollins Publishers Ltd, London. [8] Oddie, W. J. Bill Oddie's Little Black Bird Book, Eyre Methuen,London, 1980. [9] British Trust for Ornithology- Garden Bird Watch (February 2004): http://www.bto.org [10] RSPB A-Z of Birds: Great tit (February 2004): http://www.rspb.org.uk/birds/guide/g/greattit/index.asp [11] Feeny, P. P. Ecology, 51, 565-81, 1970. |
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