BIRDS OF THE UNITED STATES. 
55 
four has been laid. Incubation follows closely, usually on the day suc- 
ceeding the last deposit, and continues for nearly eleven days. This is 
not the exclusive task of the female, as the male sometimes assists her. 
When the latter is not thus occupied, it is seldom that he may be found 
in the vicinity, being absent either designedly, or in search of food. 
Should the nest be approached at this time, the female sits close, and 
seems to manifest neither timidity nor alarm. We have often surprised 
her on the nest, and reached out our hand to take her, when she would 
watch our actions very narrowly, as if seeking to study our motives, but 
remaining perfectly motionless all the while. A nearer approach was 
invariably followed by her sudden dei^arture therefrom. The bird would 
not wholly desert the nest, but demurely station herself upon an adjoining 
twig, in order to watch our actions. But with the male it is quite dif- 
erent. Any attemjjt at disturbance or pillage is resented with spirit and 
courage, especially when the nest contains young birds. 
The home of this Vireo is often chosen by the Cowbird as a place of 
deposit for her eggs. So singulaidy devoted to their alien guests do these 
foster-parents become, that they nurture them very tenderly, even to the 
neglect of their own offspring. A case is mentioned where three of these 
parasitic eggs had been deposited in the nest of the Vireo before any of 
her own. Without laying any, the female Vireo proceeded to set ujion 
and hatch the intruders. Another case is cited where two Cowbird’s eggs 
were laid alongside of two of the Vireo’s. The latter immediately stopped 
laying and proceeded to incubate. In each of these ca.ses it is evident 
that the female Vireo forewent her own maternal instincfs, and at once 
conformed to the new situation. 
The young are objects of special parental interest. From the time 
they are hatched, until the period of their leaving the nest to earn a 
livelihood, they are watched over, and fed with the daintiest fare which 
Nature affords. Caterpillars, diptera, j^lant-lice, small spiders and berries, 
constitute their earliest diet ; but as they increase in size and strength, 
other articles of a coarser nature are added. At the age of twelve days 
