146 THE BIRDS OF THE BRITISH ISLES. 



overlap the northern and western forms interbreed. The 

 former has a pure white head, ours invariably has a wide black 

 streak above the eye, and the western bird is intermediate. 

 The White-headed Tit has occurred three or four times, and 

 was first recognised as an accidental wanderer in 1852 in 

 Northumberland ; it has visited Kent and Essex and probably 

 the Shetlands. The British bird is rare in the north of 

 Scotland, but well distributed elsewhere, and is not known to 

 migrate. 



This tiny but long-tailed bird is more noticeable in winter 

 than summer ; after the breeding season it sometimes joins 

 nomadic flocks of other tits, but usually roams in family parties, 

 advertising itself by constant thin calls, zi^ zi, si, but so long as 

 the leaves are on tree and hedge it is easily hidden. It is not 

 shy, and in winter flits with constant activity and acrobatic 

 grace along the hedge or through the branches ; now and then 

 it utters a louder note, a double zee-up^ difficult to imitate. 

 The long tail assists its gymnastics, helping to balance, and as 

 the bird shoots on whirring wings from tree to tree it functions 

 as a rocket stick. The short wings and long tail give the bird 

 a top-heavy appearance, but it seldom takes long flights. 

 Seeds are occasionally eaten, but its food is mainly insects ; 

 amongst these coccids or scale insects. 



The construction of the beautiful oval nest (Plate 56) is a 

 lengthy business which employs both birds for about a fort- 

 night; the site may be a hedge, bush or, more rarely, high in 

 a tree. Felting is carried to its greatest perfection in this nest, 

 in which shredded wool, green moss, spider-silk and lichens 

 are artfully interwoven until a thick wall and dome surround 

 the five-inch oval of the " Bottle-Tit." The outside is usually 

 decorated with lichen, giving it a black and white appearance ; 

 in a hedge it is partly concealed by the lights between the 

 branches and leaves or on a lichen-covered trunk is incon- 

 spicuous ; often, however, so large a nest is easy to see, and 



