NATURAL HISTORY STUDIES 



a rafter or a chimney ; it has a lining of small 

 feathers and soft grass. The house-martin's is also 

 made of mud, strengthened with pieces of straw or 

 hair ; it is built against the wall of a house or against 

 a cliff ; it is like a bowl in shape, with its open side 

 against the surface selected, and with a small en- 

 trance near the top ; there is a lining of feathers, 

 which the martin catches in the air, and pieces 

 of straw. It is difficult to understand how the 

 bowl hangs on to a smooth surface even to a 

 vertical pane of glass ; it is interesting to watch 

 the patient carefulness of the builders, adding 

 about half an inch every morning and no more 

 till next day, so that it hardens well, the whole 

 operations lasting for about a fortnight. 



On a different line, though there is no lack of 

 connecting links, are the felt- work nests, cleverly 

 made of interwoven vegetable fibres and hair in 

 both cases a good non-conducting material. Chaf- 

 finch and goldfinch make open felt-work nests, 

 which may be eked out with spiders' webs and often 

 beautifully disguised with moss and lichen. Similar 

 constructions, master-pieces of skill, are domed in the 

 wren and the bottle titmouse, slung like a hammock 

 in the gold-crest, suspended by a string in certain 

 grosbeaks and humming-birds. There seems to be 

 no doubt that the nest is sometimes balanced 

 with lumps of earth an extraordinary device 

 when one comes to think of it. 



Among these built nests there are endless refine- 

 ments of detail. The entrance may be narrowed ; 

 the outside may be masked ; the whole may be 



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