Eurasian Blue Tit

The Eurasian Blue Tit (Cyanistes caeruleus) is a small bird in the Tit family. It is easily recognisable by its blue and yellow plumage and small size.
They nest in tree holes, although they easily adapt to nest boxes where necessary. Their main rival for nests and in the search for food is the larger and more common great tit.
The Eurasian blue tit prefers insects and spiders for its diet. Outside the breeding season, they also eat seeds and other vegetable-based foods. The birds are famed for their acrobatic skills, as they can hold on to the branches of trees and shrubs and hang upside down when looking for food.
Description
The Eurasian blue tit has an azure-blue crown and dark blue line passing through the eye, and encircling the white cheeks to the chin, giving the bird a very distinctive appearance. The forehead and a bar on the wing are white. The nape, wings and tail are blue and the back is yellowish green. The underparts is mostly sulphur-yellow with a dark line down the abdomen—the yellowness is indicative of the number of yellowy-green caterpillars eaten, due to high levels of carotene pigments in the diet. The bill is black, the legs bluish grey, and the irides dark brown.
Distribution and habitat
The Eurasian blue tit and the related hybrids are considered native species in areas of the Europe continent and in parts of The Middle East. These areas include Ireland the United Kingdom and most of the European Union. plus, Albania Algeria Andorra Armenia Azerbaijan Belarus Bosnia and Herzegovina Georgia Iran Iraq Georgia Kazakhstan Lebanon Libya Macedonia Moldova Montenegro Morocco Russia San Marino Serbia Syria Tunisia Turkey and Ukraine. 
Diet
The Eurasian blue tit is a destroyer of pests, though it is fond of young buds of various trees, especially when insect prey is scarce, and may pull them to bits in the hope of finding insects.
Voice
Eurasian blue tits use songs and calls throughout the year. Songs are used in late winter and spring to attract mates. Calls are used for multiple reasons. Communication with other Eurasian blue tits is the most important motivation for the use of calls. They inform one another on their location in trees by means of contact-calls. They use alarm-calls to warn others about the predators in the neighbourhood. Scolding, for example, is used when a ground predator (fox, cat or dog), a low flying predator or a perched owl are noticed. this is followed by mobbing behaviour in which birds gather together in flocks to counter a predator. The alarm-whistle warns other birds about a Eurasian sparrowhawk, a northern goshawk, a common buzzard or other flying predators that form a potential danger in the air.
Predators 
The small size of the Eurasian blue tit makes it vulnerable to prey by larger birds such as Jays who catch fledglings when they leave the nest. The most important predator is probably the Sparrowhawk followed by The Domestic Cat Nests may be robbed by mammals such as Weasels and Red Squirrels as well as Grey Squirrels in the UK