CHAP. I. 



INSTINCT AMONG BIRDS. 



15 



curing food and the migrations which so many un- 

 dertake. Of their skill in forming their nests we have 

 already spoken in a former volume.* The small birds 

 of Southern Africa are striking examples of this art, 

 displaying, in many instances, the most surprising fore- 

 sight in their formation. Some of the Ploceance, or 

 weaving finches, suspend their nests to the branches of 

 trees which overhang the water, shaping the fabric 

 exactly like a chemist's retort, the aperture being placed 

 at the bottom of the shank, which is eight or nine inches 

 long ; while others, it is said, fence their nests round 

 with thorns. The Icterince, 

 or hangnests of America 

 (fid' !)* as their name im- 

 plies, construct theirs on 

 the same principle, - the 

 fabric being composed of 

 the stalks of the inward 

 hair of a wiry sort of grass, 

 the blades and stems of 

 which they weave together, 

 and hang to the extremities 

 of lofty trees : in the forests 

 of Brazil, we have seen set- 

 tlements thus formed of 200 

 or 300. The pensile warbler (Sylvia pensilis Lin.) shows 

 equal ingenuity: her nest is formed of dry blades of grass, 

 the ribs of leaves, and very small roots, all twined together 

 in the most skilful and artificial manner, formed into a 

 compact ball, and carefully worked into binders, again 

 suspended to a netting which she has previously drawn 

 from tree to tree, so that this curiously constructed 

 mansion rocks to and fro with the wind, secure from 

 the assaults of her numerous enemies. The mode which 

 these little artificers pursue, is not, however, always the 

 same but varies with that instinct which, it has been 

 already remarked, is observed so frequently to suit itself 

 to new and peculiar circumstances : and thus, in our 



* Classification of Birds, vol. i. 



