Eurasian Blue Tit (Cyanistes caeruleus): Facts and Habitat

What does a blue tit look like?

The blue tit is one of Europe’s most colorful common birds. It has a bright sky-blue cap, a white face with a dark blue line through the eye, and a dark collar that runs around the cheeks to the chin. The back is yellowish green, the wings and tail are blue with a white wing bar, and the underparts are sulfur yellow with a faint dark line down the belly.

The yellow color comes from carotenoid pigments in the bird’s food, especially green caterpillars. Birds that eat more caterpillars as chicks tend to be brighter yellow. The bill is short, black and pointed, ideal for picking tiny insects from leaves and buds.

Young blue tits that have just left the nest look washed out, with yellowish cheeks instead of white ones and a greenish-brown cap. They molt into adult colors by early autumn.

Ultraviolet colors

Humans see little difference between the sexes, but blue tits see a lot. Like many birds, they can see ultraviolet light, and the blue crown reflects strongly in ultraviolet. Studies in the late 1990s showed that males have a more intense ultraviolet crown than females, and that females prefer males with the brightest crowns. In other words, blue tits are sexually dimorphic in a color that people cannot see.

How big is a blue tit?

The blue tit is one of the smallest birds that visit European gardens, smaller than a house sparrow and much lighter than the great tit.

Habitat and range

Blue tits live across almost all of Europe, from Ireland and Portugal to Scandinavia and the Ural Mountains, and east into Turkey, the Caucasus and Iran. There are an estimated 20–44 million pairs in Europe, and about 3.4 million territories in the United Kingdom.

Their favorite habitat is deciduous and mixed woodland, especially oak woods rich in caterpillars. They also do well in parks, hedgerows, orchards, churchyards and gardens, even in city centers, as long as there are trees and holes to nest in. They are scarce only on high, treeless ground and some remote islands.

Most blue tits are resident and spend their lives within a few kilometers of where they hatched. Birds from the far north and east sometimes move south or west in autumn.

Taxonomy and the African blue tit split

The blue tit was described by Carl Linnaeus in 1758 as Parus caeruleus. Genetic studies in the 2000s showed that the blue tits form an early branch of the tit family, and they were moved to their own genus, Cyanistes, from Greek words meaning “dark blue”.

Blue tits in North Africa and the Canary Islands were once included in the same species. They have darker, almost black caps and different songs, and genetic work showed they are distinct, so most authorities now treat them as a separate species, the African blue tit (Cyanistes teneriffae). That split is why the European bird is now called the Eurasian blue tit. The third member of the genus, the azure tit of Russia and central Asia, sometimes hybridizes with blue tits.

The blue tit’s closest relatives in North America are the chickadees and titmice, such as the black-capped chickadee, which belong to the same family, Paridae.

Diet and feeding

Blue tits eat mainly insects and spiders, especially in spring and summer. Caterpillars are the most important food for chicks, along with aphids, small beetles, spiders, flies and insect eggs. In autumn and winter, the birds add seeds, nuts, berries and buds to their diet and are regular visitors to garden feeders.

Their feeding style is acrobatic. Light and agile, a blue tit can cling to the tip of a thin twig, hang upside down beneath a leaf or a seed head, and pry open buds and bark to reach hidden insects. They are also curious and quick to learn new ways of finding food, which is shown by the famous story of why blue tits opened milk bottles in Britain.

Behavior and social life

In spring and summer, blue tits live in pairs that defend a territory around the nest. Males sing a high song of two or three thin notes followed by a fast trill, and both sexes give a scolding “churr” when alarmed.

In autumn and winter, territories break down and blue tits join mixed flocks with great tits, coal tits, long-tailed tits, goldcrests and treecreepers. Moving together helps them find food and spot predators. At night, each bird roosts alone, often in a tree hole, ivy or a nest box, which helps it survive cold nights.

When a person or predator disturbs a sitting female, she may hiss like a snake and peck at the intruder, a habit that earned the blue tit the old nickname “Billy biter” in southwest England.

Breeding and nest boxes

Blue tits nest in holes, naturally in trees and walls, and they readily use nest boxes with a small round entrance. The female builds a cup of moss lined with hair, wool and feathers and lays her eggs in April or May, one per day. A typical clutch has 8–10 eggs, and clutches of 14 or more are recorded, which is remarkable for such a small bird. See how many eggs does a blue tit lay? for details.

The female incubates for about 13–14 days while the male brings her food. Both parents then feed the chicks, which leave the nest after about 18–21 days. Breeding is carefully timed so that the chicks hatch when caterpillars are most abundant on the trees. Most pairs raise one brood a year.

Pairs are socially monogamous, but DNA studies show that a share of chicks in many nests are fathered by neighboring males.

Lifespan and survival

Blue tits produce many young, but most die young. Only about 38 percent of juveniles in Britain survive their first year, and about half of adults survive from one year to the next. A bird that reaches breeding age lives about three years on average. The oldest ringed blue tits have lived for about 10–11 years.

Predators and threats

Adult blue tits are hunted by Eurasian sparrowhawks, owls and domestic cats. Nests are raided by great spotted woodpeckers, which can chisel through the entrances of tree holes and wooden nest boxes, as well as by weasels and squirrels. Cold, wet springs that reduce caterpillar numbers can cause many chicks to starve.

Conservation status

The IUCN lists the Eurasian blue tit as Least Concern. It has a very large range and population, and numbers have increased across Europe since 1980. In the UK, it is on the Green List of Birds of Conservation Concern, and the population has risen over the long term, though with a shallow decline since around 2008.

One concern for the future is climate change. Warmer springs make oak leaves and caterpillars appear earlier, and if the birds cannot shift their laying dates to match, chicks may miss the peak of their food supply.

Myths and facts

Myth: a blue tit is the same as a bluebird. Visitors from North America sometimes confuse the two names. Bluebirds, such as the eastern bluebird, are American members of the thrush family. The blue tit is a European member of the tit family, related to chickadees, and it does not live in the Americas.

Myth: blue tits are blue because of a blue pigment. Birds have almost no true blue pigment. The blue of a blue tit’s cap and wings is a structural color: tiny structures inside the feathers scatter blue and ultraviolet light. The yellow of the breast, by contrast, really is a pigment, taken from the bird’s food.

Myth: blue tits live on seeds and peanuts. Garden feeders make it look that way in winter, but blue tits are mainly insect-eaters. In the breeding season, chicks are raised almost entirely on caterpillars and other small invertebrates, and a single brood may need many thousands of caterpillars before it fledges.

Fact: blue tits are quick learners. Their habit of pecking through milk-bottle tops, which spread through Britain in the 20th century, became a classic example of birds learning new behavior from each other.

Blue tits and people

The blue tit is one of the best-loved garden birds in Europe and one of the most studied. Long-term research on tits in places such as Wytham Woods near Oxford has helped scientists understand bird breeding, learning and climate change. Blue tits are among the most common birds using garden nest boxes, and many nest-box cameras follow their families each spring. You can find more garden species in our guide to garden birds in the UK.