INTRODUCTORY 29 



very differently constructed nests are very common 

 in the same localities, almost one might say, side 

 by side ; whilst birds are frequently known to wander 

 far and wide, sometimes going long distances, in 

 quest of some special substance. That each type 

 of nest is admirably adapted to its special purpose is 

 unquestionable, although in numberless cases it would 

 be impossible to demonstrate the fact. This fact is 

 confirmed by another equally suggestive, and that is 

 the extraordinary amount of variation between the 

 nests of obviously closely allied species so frequently 

 remarked. I may give as examples the nest of the 

 Willow Wren, warmly lined with feathers, in com- 

 parison with that of the Wood Wren (another globular 

 structure) in which such lining is entirely absent ; or 

 the still more curious variation in the lining of the 

 nest of the Song Thrush and that of the Redwing — or 

 yet again in that of some of the Buntings' nests. 

 Perhaps we might say that the more uniform the 

 conditions of life of the species forming any group, 

 family or order may be, the more uniform will be the 

 nest type prevailing. This is specially illustrated by 

 the species composing such a large and natural order 

 as the Plovers and Sandpipers and their allies. 

 Throughout this large group the nests are remark- 

 ably uniform, the young being hatched in relatively 

 slight nests upon the ground. There are, of course, 

 one or two notable exceptions, but these only go to 

 prove the rule. The Herons form another group 



