Parus major
The largest UK tit - green and yellow with a striking glossy black head with white cheeks and a distinctive two-syllable song. It is a woodland bird which has readily adapted to man-made habitats to become a familiar garden visitor. It can be quite aggressive at a birdtable, fighting off smaller tits. In winter it joins with blue tits and others to form roaming flocks which scour gardens and countryside for food.