BIRDS — NIDIFICATION. 293 



and warm, and perfectly fitted for all the purposes for which it 

 was intended. 



Other birds build in wood. The tomtit and the 

 woodpecker excavate a hole in a tree, and carefully carry 

 away the chips, so as not to give any indication of the 

 whereabouts of their nests. Wilson says that the American 

 woodpecker makes an excavation five feet in depth, of a 

 tortuous form, to keep out wind and rain. 



The orchard starling suspends its nest from the 

 branches of a tree, and uses for its material tough kinds of 

 grass, the blades of which it weaves together. Wilson 

 found one of these blades to be thirteen inches long, and 

 to be woven in and out thirty-four times. 



We may next notice the weaver (Ploceus textor) and 

 tailor {Prinia, Orthotomus, and Sylvia). The former 

 intertwines slender leaves of grass so as to produce a web 

 sufficiently substantial for the protection of its young. 

 The tailor-birds sew together leaves wherewith to make 

 their nests, using for the purpose cotton and thread where 

 they can find it, and natural vegetable fibres where they 

 cannot obtain artificial. Colonel Sykes says that he has 

 found the threads thus used for sewing knotted at the 

 ends.^ 



Forbes saw the tailor-bird of the East Indies construct- 

 ing its nest, and observed it to choose a plant with large 

 leaves, gather cotton which it regularly spun into a thread 

 by means of its bill and claws, and then sew the leaves 

 together, using its beak as a needle, or rather awl. 



This instinct is rendered particularly interesting to 

 evolutionists from the fact that it is exhibited by three 

 distinct genera. For, as the instinct is so peculiar and 

 unique, it is not likely to have originated independently in 

 the three genera, but must be regarded as almost certainly 

 derived from a common ancestral type — thus showing that 

 an instinct may be perpetuated unaltered after the differen- 

 tiation of structure has proceeded beyond a specific distinc- 

 tion. The genus Sylvia inhabits Italy, the other two 

 inhabit India. Sylvia uses for thread spiders' web col- 



* Catalogue of Birds, &c., p. 16. 



