39O LIFE-HISTORIES OF BIRDS 



Nest building has been observed as early as 



March 15, but then only in sheltered localities on 



the south slopes of hills. Here the nests are built 



most generally in the branches of coniferous trees. 



Usually but a single brood is reared in a season ; 



but we have met with a second brood when the 



weather has been unusually propitious. In such 



cases the first batch of young appeared about the 



middle of April, and the other early in July. 



Nidification ordinarily commences from the 2Oth 



to the 28th of April. A nest is the product oi the 



joint labor of the sexes for a period of six days, 



working with considerable diligence. The day 



following the completion of the nest, the female 



begins to deposit her eggs to the number of six, 



at the rate of a single ovum per day. Incubation 



follows on the day succeeding the last deposit, and 



is the sole business of the female for about sixteen 



clays. The male-bird keeps very close watch over 



his partner in the nest, when not employed in 



providing nourishment for her and himself. When 



the nest is assailed, both parents seek to drive 



away the intruder by loud clamors and threatening 



gestures; flying close to his head with open jaws 



and fury-darting eyes. Where the offender has 



been one in feathered dress, we have known 



several pairs to come to the assistance of their 



besieged friends, when the most deafening cries 



and wildest excitement would prevail. Such is the 



bravery with which some parents defend their 



nests and young, that in encounters with human 



