BIRDS— NIDIFIC ATION . 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 are said to 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 5 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 (Pmm, 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 . 1 
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 
bv 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 cob 
1 Catalogue of Birds, &c,, p. 16, 
