ADAPTATION TO HAUNTS 157 



rabbit's burrow may be utilised if it is suitable. The single 

 egg, in marked contrast to that of the guillemot and razorbill, 

 is typically of a dull white colour. The numbers of puffins 

 are often to be reckoned in thousands, in spite of severe 

 persecution. Thirty years ago Professor Newton estimated 

 the tenants of one haunt in the Hebrides at three millions. 



§ 8. Birds in Other Haunts 



We need not pursue the inquiry further, for all that we 

 are aiming at in this book is a suggestion of points of view. 

 In the first part of this chapter we gave examples of special 

 adaptations to diverse types of environment, such as trees 

 and the open sea — to mention two which are very far apart. 

 In the later paragraphs we have been suggesting the study 

 of birds in their more detailed haunts. Just as there are 

 " plant associations " characteristic of the seashore, the 

 marsh, the pond, the wood, the mountain-side, and other 

 haunts, so there are " bird associations " which are well- 

 defined, for part of the year at least, and we have instanced 

 mountain birds, moorland birds, and sea-cliff birds. 



There are obviously other associations. Thus there are 

 marsh birds, like the bittern and the crane, and the fact that 

 neither is any longer a breeding bird in Britain, where they 

 once were common, suggests the general remark that the 

 spread of agriculture and the involved draining operations 

 must mean the dwindling of marsh birds. Apart from small 

 birds like reed- warbler and marsh titmouse, for which a 

 limited area suffices, the marsh birds of an agricultural 

 country are bound to be eliminated, unless indeed it is a 

 country of innumerable lakes. Perhaps it would not be 

 unfair to call the heron a persistent marsh bird, for although 

 " heronries " are usually on lofty trees, much of the feeding 

 is on marshy ground. By lochs as well as by the riverside 

 we watch these elegant birds, with their extraordinarily 

 alert immobility, waiting for an eel or some other victim to 

 come within striking range. For the breeding season the 

 Black-headed Gulls may be justly called marsh birds, for 

 they take full advantage of the treacherous swampy ground. 



