THE BIRDS 273 



These strange performances are usually confined to the male 

 birds, but in some cases the female joins in the dance. Mr. 

 Nelson, in his " Birds of Alaska," describes the behaviour of a pair 

 of stately cranes, who hopped and bowed and pirouetted together 

 in the most ceremonious and ridiculous fashion ; and similar ex- 

 hibitions have been witnessed in several different species of bird 

 by reliable observers. In certain species the r61es of the male and 

 female are reversed, and the female bird courts the male ; when 

 this is the case the female is always the finer and more brilliantly 

 coloured of the two. 



In their nest-building habits birds show a remarkable degree 

 of diversity. Many, indeed, do not build nests at all, but simply 

 lay their eggs on the bare ground, usually in a slight depression ; 

 others collect a few sticks, dried leaves, or pieces of seaweed, 

 according to their kind, to form a rough sort of bed ; some utilise 

 holes in rocks, in the ground, in hollow trees, as nurseries ; some 

 dig holes for themselves in the earth with the aid of beak 

 and claw ; while amongst those birds that build actual nests the 

 nests vary from a rude, shapeless jumble of twigs, grasses or other 

 odds and ends, to the most beautiful and elaborate structures. 

 All manner of materials, too, are used in making the nest moss, 

 twigs, grass, wool, hair, cotton, feathers, mud, lichen, cobwebs, 

 and the rootlets and seeds of various plants. 



Amongst the birds that nest in burrowed holes are the sand- 

 martin, bee-eaters, kingfishers, some of the penguins and the 

 puffins ; the latter habitually breed in rabbit-holes on the edge of 

 cliffs, but, if these are not available, will burrow for themselves or 

 deposit their eggs in crevices of rocks ; holes in trees are used by 

 the owls, wrynecks, and woodpeckers. Simple ground-nests are 

 made by swans, ducks, geese, waterhens, and corncrakes ; platform 

 nests are constructed in trees, rocky ledges, or on the tops of build- 

 ings by turtle-doves, ringdoves, eagles, cranes, and storks. Swallows, 

 flamingoes, and tree-creepers use mud to build their nests ; thrushes 

 use mud in conjunction with other materials, such as moss, roots, 

 and grass. Beautifully woven, cup-shaped nests are made by 

 chaffinches, redstarts, and goldfinches ; the nests of wrens, water- 

 wagtails and some of the tits are domed, one of the most beautiful 

 examples being the work of the long-tailed tit (Acredula caudata). 

 This nest is made of moss and wool bound together with spiders' 

 s 



