BIRDS' NESTS 



The tunnel of the sand-mattin, for instance, 

 driven for two feet or more into the hard bank, or 

 the nest of the house-martin, built up of tmy pellets, 

 each adhering to the one below, the whole swelling 

 gracefully outwards and gauged to an inch to meet 

 the overhanging eave — these, when onty frail beaks 

 and tiny claws are available, are, without question, 

 remarkable feats of engineering. 



It would be mteresting to know why certain 

 birds have decided to build nests with a roof when 

 the majority conclude that no cover is necessary. 

 Strangely enough, the birds which lay in the most 

 exposed situations — on rocks and barren moors — 

 the guillemot, razorbill, and curlew, for example — 

 are those which take the least trouble to provide 

 any shelter for their coming families. The wren, 

 wood-wren, willow-wren, long-tailed tit, and others, 

 which are dome-builders, almost invariably select 

 sites which are well protected by trees and under- 

 wood from the inclemency of the weather. 



Mud is a material which many birds use in the 

 process of nest construction, some employing it 

 exclusively for the outer structure, whilst others 

 combine it with sticks, straws, etc. The magpie 

 introduces a large quantity of mud into the thorny 

 edifice which it erects in the tree-tops, and the 

 song thrush adopts it, m conjunction with decayed 

 wood, for a lining. The house-martin and the 

 swallow, however, are the true mud-builders. Their 

 method is to collect tiny pellets from the margins 

 of ponds and from road-side puddles, and to build 

 up the nest, brick by brick. The swallow has 

 added an improvement which certainly tends to 

 security. It first selects a short stick or fibre, and 

 this it rolls in the mud. As the ends project the 

 pellets thus formed are " tied m " one with another 

 and thus the nest-walls are held together with 



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