296 BRITAIN^S BIRDS AND THEIR NESTS. 



times to kill small and weak birds. The smaller and 

 weaker Coal-Titmouse {Pants ater) has adopted a more 

 vegetarian diet, eating seeds as well as insects, and feeding 

 on the ground as well as among trees. The delicate little 

 Blue Titmouse {Partis cceruleus), with its very small bill, 

 feeds on the minutest insects and grubs, which it extracts 

 from crevices of bark and from the buds of fruit-trees. 

 The Marsh-Titmouse, again {Parus palustris), has received 

 its name from the low and marshy localities it frequents ; 

 while the Crested Titmouse {Parus cristatus) is a northern 

 bird frequenting especially pine-forests, on the seeds of 

 which trees it partially feeds.' In the last two cases there 

 is a difference of haunts and general area respectively ; 

 but in the case of the first three the chief divergence is 

 one of feeding habits, although the Coal-Tit is perhaps 

 more often found in the depths of the forest than are its 

 allies. The Long-tailed Tit belongs to another genus, 

 and differs in a number of ways. 



This case of divergence in mode of life, in the Great, 

 Coal, and Blue Tits especially, well illustrates our point. 

 As the famous naturalist just quoted puts it, a species 

 which would otherwise be in severe competition with a 

 perhaps better-equipped rival, adapts itself slightly ' to fill 

 a vacant place in nature' where competition is less. But 

 not only is the individual species benefited, and perhaps 

 saved, but the maximum of life which the area can sup- 

 port is more nearly attained by this diversity of habit or 

 form. It is well known that a farmer can get a larger 

 crop of hay by sowing together a number of different 

 grasses, clovers, and the like, than by sowing more of 

 one or two. The general principle is the same. 



The Great Tit itself is a resident and abundant species 

 throughout all our area, except the extreme north of Scot- 

 land and the outlying isles. Its distinguishing features 



