WILLOW WARBLER 



unusual to find a late second brood in the case of this species, 

 and the fact of the first female building a third nest points 

 in the same direction, and is evidence of expectation on her 

 part. Failure, however, was the result, brought about, I 

 believe, solely by abnormal conditions. 



I have not yet noticed any striking variation in the duration 

 of the period between the arrival of a female in a given territory 

 and the laying of the first egg. So far as my observation goes 

 this period is from seven to nine days, but since there is con- 

 siderable variation in this respect in the case of other species, 

 it is possible that it is really greater than the above figures 

 represent it to be. 



The female commences to build about two days after her 

 arrival. Deducting these two days from the normal period of 

 fertilisation, which is approximately eight, we get six days for 

 the actual construction of the nest. This need not necessarily, 

 and probably does not, represent the building capabilities of 

 the bird ; for with regard to rapidity of construction the 

 female must be guided by the development of her ovaries. It 

 will be remembered that the first female in No. 2 territory 

 constructed her second nest in less than four days, and the 

 second female her one nest in less than three. Under ordinary 

 conditions a female builds rapidly for a short time and then 

 ceases, and the greater part of the work seems to be done 

 during the first few hours of daylight, for, before leaving a 

 territory, I have taken particular notice of the details of a 

 certain nest, and upon arrival the following morning have 

 found nothing added thereto. The greater part of the actual 

 construction is the work of the female, the male seldom, if 

 ever, attempting to share this duty with her, but it is no 

 uncommon occurrence for him to interrupt the process by 

 flying at her and pursuing her through the bushes. Sexual 

 desire is the cause of this, as it is the period of fertilisation. 

 Although dead grass and dead leaves are made use of to a large 

 extent in the construction of the nest, it is worthy of notice 

 that in many instances the bark of the honeysuckle is utilised, 



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