226 NORTH AMERICAN BIRDS. 



The wonderful sagacity displayed by this Warbler in avoiding the disa- 

 greeable alternative of either having to abandon its own nest or of rearing 

 the young of the intrusive Cow Blackbird, when one of these eggs is dropped 

 in her nest, was first noticed by Mr. Nuttall. The egg of the parasite, being 

 too large for ejectment, is ingeniously incarcerated in the bottom of the nest, 

 and a new lining built over it. Occasionally, either by accident or design, 

 the intrusive egg has been fractured. Mr. Nuttall states that where the 

 parasitic egg is laid after her own, the Summer Yellow-Bird acts faithfully 

 the part of a foster-parent. This, however, is not according to my observa- 

 tions. In several instances I have known the Summer Yellow-Bird uttedy 

 refuse to act the part of a foster-parent, and, rather than do so, sacrifice her 

 own eggs. So far as I know, this Warbler will never sit upon or hatcli out 

 the egg of the Cowbird, under any circumstances. Some powerful instinct, 

 bordering closely upon reason, seems to teach these intelligent Warblers the 

 character of the intruder, and they sacrifice their own eggs rather than rear 

 the parasite. In this dilemma they will always, so far as I know, incarcer- 

 ate their own eggs with the Cowbird's and reconstruct the nest above them. 

 In one instance the same pair of Yellow-Birds twice, in the same nest, cov- 

 ered up alien eggs in this manner, building, in fact, three nests one above 

 the other, between the walls of which had been successively included two 

 eu'ss of the Cowbird. This three-storied nest measured seven inches in 

 length, and was built almost exclusively of raw cotton. The covering of the 

 imprisoned eggs was about two thirds of an inch thick. In both instances 

 the Cowbird's eggs had been broken, apparently l)y design. 



So far as I am aware tins Warbler raises but one brood in Massachusetts 

 in a season. In Pennsylvania it is said to raise two, and even three. The 

 eggs are usually five and occasionally six in numlier. 



This Warbler is conspicuous in its devotion to its young, evincing a strong 

 attachment and an anxiety in regard even to an unoccupied nest, and be- 

 traying the site by this solicitude. They will also resort to various expedi- 

 ents to draw one away from their nest, by feigned lameness and other strata- 

 gems and manoeuvres. 



The song of the Summer Yellow-Bird is simple but pleasing, and is easily 

 recognized when once know^n, though liable to be confounded with that of the 

 Maryland Yellow-Throat, and also said to resemble the song of several other 

 Warblers. 



In confinement they usually beconre very tame, confiding, and reconciled 

 to tlieir imprisonment, and have been known to perch on an outstretched 

 finger, and to catch files in a room. 



Their eggs vary in length from .61 to .70 of an inch, and in breadth from 

 .49 to .52. They have a ground-color of a light green. Their dots and 

 blotches vary greatly in number, size, and manner of distribution. Their 

 colors are light purple, darker purplish-brown, and other shades of brown 

 and lilac. 



