MARSH WARBLER 



this will have to be generally evolved in the future, though 

 perhaps not so needlessly strong as is sometimes the case 

 even now. One other feature with regard to the nest deserves 

 mention, and this is the depth of the foundation. Every 

 nest is by no means alike in this respect ; for whereas in 

 one case the foundation may be of the normal depth, in 

 another there may be a solid platform of dead grass measuring 

 between two and three inches. So that here again the 

 variation is considerable, and it is difficult to see what useful 

 purpose can be served by the increased labour that is some- 

 times bestowed upon it. 



From four to five eggs appear to be the normal clutch of 

 the species. On the average one egg is laid every twenty-four 

 hours, either during the night or the early hours of the 

 morning. Incubation lasts about twelve days and during this 

 period the excitement of the male becomes appreciably less. 

 He nevertheless shows signs of irritation when his territory 

 is intruded upon by another male of his own or another 

 species, and displays it in the manner already described. His 

 song decreases gradually in strength, being confined in a great 

 measure to the early hours of the morning, and even then it 

 can scarcely be compared to its former glory. Both sexes share 

 in the duties of incubation, and they often relieve one another 

 approximately every half-hour. While one of them is engaged 

 in incubating, the other occupies its time in searching for 

 food, preening its feathers, or pursuing an intruder. The 

 changing of places is done stealthily. The relieving bird does 

 not fly directly to the nest, but approaches it slowly by hop- 

 ping from stem to stem through the dense undergrowth, so 

 that one is oftentimes made aware of the change solely by the 

 shaking of the various plants as the bird travels amongst 

 them. The one that is being relieved slips off the nest quietly 

 and disappears, leaving scarcely any trace of its departure. 

 How far they are aware of one's presence and how far their 

 conduct is affected thereby is difficult to say, but they are 

 decidedly more timid than the Eeed Warbler under similar 



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