The Eurasian blue tit

Family - Paridae

Genus - Cyanistes

Species - Cyanistes caeruleus

Blue tits are very distinctive small birds. They have a bright blue cap of feathers over their heads, and have blue/green back and tail feathers, with a yellow/green breast. Males are females look almost identical to the naked eye, however reports suggest that under ultraviolet light, males have a slightly lighter blue crown. Juvenile blue tits are often more yellow than blue, and the blue colouration develops as these birds grow. These small birds are resident to the UK, and much of Europe, and they may be seen in gardens, hedgerows, courtyards, parks and woodland.

Blue tits are often around 12cm long with a wingspan of just 18cm! Blue tits feed on a diet of primarily insects, seeds and in particular, caterpillars. Over winter, blue tits may form large flocks of 20+ in order to find food. Interestingly, it is believed that the yellowness of the bird's underbelly indicates how many yellow-green caterpillars the bird has eaten, due to the high levels of carotene pigments in this type of prey.

These birds nest in any small hole in trees, walls or buildings, and prefer nest boxes with only a small opening. The biggest competitors with blue tits for nest sites are the great tit and house sparrow. Blue tits are fiercely protective of their clutch of eggs, and will defend them against any intrusions. In the south-west of the UK, this behaviour has earnt these birds the title "little billy biter". Blue tits usually use moss, dead leaves, hair and feathers in their nests, and eggs will be laid in April-May, with up to as many as eight in any one clutch. This is important, as a study conducted using ring-recovery data suggested that the survival rate of young blue tits in their first year was just 38%!

The average lifespan of these birds is just 3 years, however in the UK, the oldest recorded blue tit had reached the ripe old age of 10 years. Blue tits do use song to defend territory and to attract mates, just like the blackbirds and robins I have previously described. The use of song is also used as a method of communication between blue tits in an area, using "contact-calling" to inform each other of their presence, or using "alarm-calling" to alert others to danger. Blue tits have also been known to perform a "mobbing" behaviour, in which the birds may gather into a flock to drive any predators away.

The blue tit is listed as "Least concern" on the IUCN red list, however it does have numerous natural predators and threats. Blue tits are predated upon by sparrowhawk and weasels, and jays and grey squirrels will take young from the nest. Blue tit survival is also heavily affected by the weather, and a significant cold snap may severely increase blue tit mortality. It may also affect the availability of these bird's main prey, the caterpillar. With too few caterpillars, these birds may not be able to raise a brood. But as with many bird species, we can help these little guys out by supplying them with any leftovers suitable, such as cake, biscuits, cheese, old meats and fat. They are particularly a fan of suet!