Moss - BBC Springwatch British wildlife

Paul Hobson/FLPA

Herbert Kehrer/Imagebroker/FLPAp

Blue tits and great tits are originally woodland birds, which have readily adapted to life in our gardens.

Of all the stars of Springwatch, perhaps none is quite so enduringly popular as the blue and great tits. Their antics, as they jostle for position on feeders, their cheeky behaviour and, above all, their life-or-death struggles as they bring up a brood of chicks under the glare of TV cameras, make them utterly compelling to millions of viewers.

There is one simple reason why these birds have become such stars: they choose to nest in bird boxes, which means that from the earliest days of live TV broadcasts certainly as far back as the early 1990s and Bird in the Nest it was possible to put cameras into their nests. Things have changed a lot since then, of course: instead of huge cameras, we now have a battery of tiny high-definition cameras that can view the nesting birds at all angles, without causing them a moments disturbance.

The reason tits take so readily to nest boxes is that these artificial homes are an ideal substitute for the natural holes and crevices in which these birds nest. For, like so many of our garden birds, tits are originally birds of the woodland or woodland edge. They have made their homes in our gardens primarily because we provide plenty of food for them not just in the shape of seeds and peanuts but also through what we plant, which provides much-needed moth caterpillars for their hungry broods.

And broods dont get much hungrier than a dozen baby blue tits, all crammed into their soft, cup-shaped nest of moss and feathers, inside a tiny wooden box. During the dozen or so days between the chicks hatching and when they finally fledge and leave the nest, a single brood may require as many as 12,000 caterpillars thats 1,000 caterpillars per day, or roughly one caterpillar every two minutes for each of the two parents. No wonder the adult birds look so tatty and exhausted by the end of the breeding season!

Blue and great tits are the two species we often feature on Springwatch, along with occasional appearances by a third garden species, the coal tit. These three are easy to tell apart: the great tit, as its name suggests, is larger than the other two, and has a smart black and yellow plumage with a green back, white cheeks and a thick black strip down its front. Blue tits are smaller, mainly blue and yellow, and also with white cheeks (though the youngsters have yellow cheeks). Coal tits are basically a monochrome version of the blue tit similar in size, with, a black, brown and grey plumage and a distinctive white patch on the back of the neck, or nape.

Three other kinds of tit breed in Britain, two of which, the marsh and willow, are so similar that they werent separated as different species in Britain until the last year of the nineteenth century. Both are superficially similar to the coal tit, being mainly brown with a black cap, but they are both larger and less varied in plumage, and lack the coal tits white nape. Sadly, both marsh and willow tits have suffered major declines in recent years, perhaps due to a loss of suitable breeding habitat.

The final species, the crested tit, is found only in the ancient pine forests of Speyside in Scotland, and can easily be identified by its perky crest. Two other species with tit in their name, the long-tailed tit and the bearded tit, are in fact unrelated to the tits, though long-tailed tits do often accompany flocks of tits in winter.

Unlike many other nesting birds featured on Springwatch, both blue and great tits usually have only one brood of chicks in a season. As they generally live for only a year or two as adults, this is a risky strategy: literally putting all their eggs in one basket. In years when spring comes very early, as in 2007 and 2011, this can mean that by the time the birds begin to nest, the moth caterpillars on which they so depend are already coming to the end of their lifecycle and beginning to pupate, which can mean very bad years for the birds. It remains to be seen whether these species are bringing their own breeding season significantly earlier to cope with this change. Evidence suggests that they probably are.