The Eurasian Blue Tit (Cyanistes caeruleus) is one of Sweden's most familiar garden birds, its cobalt-blue crown, white face and bright yellow underparts making it unmistakable at any feeder. The male shows a black eye-line and moustache stripe, an olive-green back, and blue wings with a white wing bar; the female is nearly identical but with a slightly duller crown and paler yellow underside, while juveniles are readily told apart by yellowish rather than white cheeks. Measuring just 11-12 cm and weighing 9-12 g, it is small enough to hang upside down from thin twigs and feeders, out-competing far larger birds for food through sheer acrobatic skill.
The song is a fast, trilling, descending "tsi-tsi-tsi-hu-hu-hu", often starting as early as January in mild winters, with a sharp "tsii" contact call and a rasping "churr" given in alarm. Blue Tits are found throughout Sweden except the far northern mountains, in deciduous and mixed woodland, parks and gardens, with a population of 1-2 million pairs. They are cavity nesters, using tree holes and nest boxes with a hole of just 26-28 mm, a millimetre or two smaller than a Great Tit prefers, which helps keep that larger, more dominant competitor out. The 8-12 white, red-spotted eggs are incubated for 13-14 days by the female and hatch to coincide with the spring boom in aphid larvae, forcing both parents into hundreds of feeding visits a day to satisfy the brood. Outside the breeding season Blue Tits often join mixed flocks with Great Tits and Crested Tits, and diet shifts from insects and larvae in summer to seeds, nuts and suet in winter. Most individuals live only two to three years in the wild, though ringing records show some surviving past ten.
Read about this species in Swedish →