THE SUMMER YELLOW BIRD, 83 



wool ; where abundant, I have known instances where nests were built almost exclusively of one or the 

 other material. A pair of these birds, in 1836, built their nest under a parlour window in Roxbury, 

 where all their operations could be closely watched. When discovered, only the framework, the 

 fastening to the supporting twigs, had been erected. The work of completion was simple and rapid. 

 The female was the chief builder, taking her position in the centre of the nest and arranging the 

 materials in their places as her mate brought them to her. Occasionally, with outstretched wings and 

 expanded tail, she would whirl herself round, giving to the soft and yielding materials their herni- 

 sphei'ical form. At intervals she arrested her revolutions to stop and regulate with her bill some un- 

 yielding portion. "When her mate was dilatory, she made brief excursions and collected materials foi 

 herself, and when the materials brought her were deemed unsuitable they were rejected in a most 

 summary and amusing manner. The important part of the tail-feathers in shaping the nest and 

 placing the materials in position was a striking feature in this interesting performance. The 

 greater portion of the nest was thus constructed in a single day. The wonderful sagacity dis- 

 played by this Warbler in avoiding the disagreeable 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 into 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. Occa- 

 sionally, either by accident or design, the intrusive egg has been fractured. Mr. Nuttall states that 

 when the parasitic egg is laid after her own, the Summer Yellow Bird utterly refuses to act the part 

 of a foster-parent, and rather than do so sacrifices her own eggs. So far as I know, this Warbler 

 will never sit upon or hatch out the egg of the Cow-bird 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, incarcerate their own eggs with the Cow-bird's, and re-construct the nest 

 above them. In one instance, the same pair of Yellow Birds, twice in the same nest, covered up 

 alien eggs in this manner, building, in fact, three nests one above the other, between the walls of 

 which had been successfully included two eggs of the Cow-bird. This three-storeyed 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 Cow-bird's eggs had been broken, 

 apparently by design. So far as I am aware, this 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 occa- 

 sionally six in number. This Warbler is conspicuous in its devotion to its young, evincing a strong 

 attachment and an anxiety even in regard to an occupied nest, and betraying the site by this 

 solicitude. They will also resort to various expedients to draw one away from their nest by 

 feigned lameness and other stratagems and manoeuvres. 



"The song of the Summer Yellow Bird is simple but pleasing, and is easily recognised when once 

 known, 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 become very tame, confiding, and reconciled to their imprisonment, 

 and have been known to perch on an outstretched finger and to catch flies 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- 

 colour of a light green. Their dots and blotches vary greatly in number, size, and manner of distribu- 

 tion. Their colours are light purple, darker purplish-brown, and other shades of brown and lilac." 



