REED WARBLER 



whether they are able to distinguish the call-note of their own 

 from that of other young, it is difficult to say. The same 

 factor which we discussed earlier no doubt guides them in 

 regard to feeding in rotation ; those that are the more hungry 

 are possibly the more persistent in uttering their call-note and 

 do so the more loudly. Owing to the conditions under which 

 they are born and reared it is probable that there is a very 

 considerable mortality amongst them, any tendency to weak- 

 ness being rigorously eliminated. The young of other species 

 of the same genus are comparatively secure even upon the 

 ground, and can, indeed, often be found after they have left 

 the nest hidden amongst the undergrowth. But the young 

 Reed Warblers must be prepared to take their place in the 

 struggle for existence immediately they leave the nest ; any 

 weakness that would prevent them from indefinitely clinging 

 to the reeds until capable of considerable powers of flight 

 would be fatal and could only result in their destruction ; and 

 to meet this difficulty it probably is the case that they remain 

 in the nest longer than those of some other closely allied 

 species, since any tendency to leave it too early would be held 

 in check. The weakling would neither be able to withstand 

 the cold, wet weather, nor could it keep up with its parents or 

 even attract their attention when desirous of food. In fact, 

 the struggle for existence must, in their case, be exceedingly 

 severe. 



Throughout the whole of June and July periodical out- 

 bursts of excitement occur amongst the different individuals 

 inhabiting the reed bed, such outbursts being apparently not 

 confined to one sex only, although in most instances the 

 males are probably the sole actors. To determine what are 

 the causes which lead up to these activities is difficult ; it is 

 not even possible to decide whether the participators are in 

 earnest and the struggles genuine, or whether their behaviour 

 is an expression of exuberance of energy. Play forms an 

 important part in the life-history of many mammals. The 

 rabbit, the hare, or the fox can be seen practising for the 



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