Blue tit

Small in size but easily identifiable given its lush colours, the Eurasian blue tit (Cyanistes caeruleus) is one of the most emblematic birds in the Portuguese avifauna. This bird from the Paridae family is fearless and restless and moves easily through tree branches looking for insects, its main diet.

Blue tits are about 12 centimetres long, weigh no more than 12 grams on average and stand out for its vibrant plumage. As for their head, it looks like they are wearing a blue cap, in strong contrast with their white face and the thin black line that crosses their eyes, resembling a mask. Their back is olive green, the wings and tail are blue and the chest and belly range from yellow to white. The beak and paws are dark grey. In the Summer, juveniles have yellow cheeks and a greyish-green cap.

Spread throughout Europe to north-west Africa and parts of western Asia, the blue tit can be found in Portugal virtually all over the national territory and prefers forest areas, parks and urban gardens. Oak, pine, and eucalyptus forests, and cork oak forests and locations with old trees, are especially appealing to this species.

Its diet is diverse and changes according to the season. During the Spring and the Summer, it feeds predominantly on insects (especially lepidopteran larvae), spiders and other invertebrates, thus making this bird a strong ally in pest control (including mealy bugs and aphid control). In autumn and winter, when there are less insects to feed on, the blue tit adapts and feeds on seeds, berries and fruits. In the gardens, we often find them in the feeders, where they eat peanuts, sunflowers and fat balls, in particular. Its main natural predator is the hawk, but other animals, such as weasels, squirrels and jays, visit their nests and feed on their eggs.

When the breeding season arrives, this bird species nests in cavities, mainly in old trees or holes in the walls, but adapts easily to other structures, such as nest boxes installed by The Navigator Company at Herdade de Espirra, one of this company’s biodiversity centres.

The females build the nests using soft materials such as straw, fur, feathers, and moss. Their breeding season begins in the spring in Portugal, usually in April, but it may vary depending on the region. Blue tits lay 7 to 12 eggs, which hatch for about two weeks. Juveniles leave the nest approximately three weeks later but keep being fed by their parents for some time afterwards.

Energetic, gymnast and clever

Blue tits are highly social birds and often fly in small flocks with other tit species, especially in the winter. They are known for their acrobatics when foraging for food, hanging upside down and moving quickly between branches and leaves. Its singing is a melodic and joyful trill, and we can hear it often in wooded areas and gardens.

But this fun little bird does not stand out for its beauty and energy alone. The blue tit is also known for its ability to learn and adapt whenever its survival requires it.

See, for example, the famous story of blue tits opening milk bottles in the UK. This phenomenon is well-documented and fascinated ornithologists and the general public back in the day. They were spotted for the first time doing this in the 1920s and became a common practice in the 1950s and 1960s as they often visited door sills to try to feed on the milk cream underneath the bottle caps. This behaviour seems to have disappeared mostly due to changes in milk packaging and delivery/purchasing methods. However, it was considered a remarkable example of social learning among birds.

Although small in size, the blue tit plays a large and crucial role in the ecosystems they live in. Their presence in parks and gardens brings life and movement, while their eating habits help control insect populations thus avoiding pests. This is an added value for the balance of ecosystems.

Did you know that…

• It is an extremely restless and acrobatic bird that moves quickly between the canopies and branches of trees and is often spotted feeding upside down.
• It’s among the species that use bird feeders most, especially in winter. However, it prefers to hunt for food and feed its chicks on spiders, caterpillars and other insects.
• It can lay up to 16 eggs, thus holding the record among small birds. After they are born, parents have to make hundreds of flights a day to feed so many chicks.
• When they reproduce, female blue tits tend to eat bits of old snail shells, thus restoring the calcium levels needed to form the eggshells.