MARSH WARBLER 



faces. A certain quantity of food may be necessary to set the 

 machinery at work, to stimulate, that is to say, the nerves 

 which control defecation ; and this quantity may only be 

 supplied to the first of the two offspring, and the second, 

 though partially satisfied, may neither receive sufficient to 

 bring about a similar result, nor to allay the hunger to such 

 an extent as would make it incapable of the necessary effort to 

 obtain the major share at the next opportunity. The whole 

 system has probably been built up to bring about a certain 

 definite result, and that result is the cleanliness of the nest. 

 I have already called attention to the importance of cleanli- 

 ness in this respect, and have pointed out that young birds 

 could scarcely thrive in an insanitary nest. The perfection of 

 the system can be better understood if we imagine the present 

 regular method abolished. The young would then be fed 

 accidentally, defasoation would occur at no specified time, 

 the faces would be overlooked, and the nest consequently 

 contaminated. Perfect as the system is, even now it does not 

 always ensure complete cleanliness, for the faces are occa- 

 sionally allowed to remain in the nest. Experiments made 

 with leaves placed in the nest bring about results very similar 

 to those already referred to in the life of the Eeed Warbler. 

 A leaf is picked up by the parent and held for a few moments ; 

 it is then dropped, but again picked up and perhaps carried 

 away or again dropped. Even when the faces are there 

 awaiting removal a leaf may be carried away in place of 

 them. However, it is well to state that considerable hesita- 

 tion is displayed in their attitude towards such an obstruc- 

 tion; no doubt the interruption of the instinctive procedure 

 is sufficient to account for their bewilderment. 



The young are completely naked at birth, no down being 

 visible, and the eyelids are sealed. Eor the first two days or 

 so no very great change in their growth is perceptible, but on 

 the third day the primaries become visible. Between the 

 third and fourth days a considerable change takes place, the 

 feathers sprouting on all the tracts, and the primaries being 



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