CHESTNUT-SIDED WARBLER 371 



dried grasses or straws and placed them around to form the sides of the nest 

 and bound them to the branches with more caterpillars' webs. Having finished 

 the sides, she put in a lining of soft grasses, fine rootlets and plant fibers. This 

 nest when completed at the end of five days was much less bulky than the usual 

 nest of the Yellow Warbler, and much firmer, with walls not more than one- 

 fourth as thick. 



Eggs. — Four eggs seem to form the usual set for the chestnut-sided 

 warbler, but this sometimes consists of only three, or more rarely five. 

 The eggs are ovate, sometimes tending toward elongate ovate, and 

 they have only a slight lustre. The ground color may be white, creamy 

 white, or very pale greenish white. They are speckled, spotted, and 

 blotched with "auburn," "bay," "Brussels brown," "raw umber," 

 "chestnut-brown," "cinnamon-brown," "mummy brown," or "Mars 

 brown," with undertones of "dark brownish drab," "pale brownish 

 drab," or "light purplish drab." The color and amount of the mark- 

 ings vary considerably, ranging from eggs that are delicately spotted, 

 or speckled only with drab colors, to those boldly blotched with browns 

 that form a solid ring around the large end, completely covering the 

 undertones. On some the spots are scattered over the entire surface, 

 but generally they are concentrated and tend to form a wreath, A 

 few eggs have the spots confined to a tight, narrow ring, leaving the 

 rest of the surface almost immaculate. The measurements of 50 eggs 

 average 16.7 by 12.4 millimeters ; the eggs showing the four extremes 

 measure 18.0 by 12.5, 17.3 by 13.2, and 15.2 by 11.7 millimeters (Harris) . 



Young. — The period of incubation for the chestnut-sided warbler 

 seems to be between 12 and 13 days; Frank L. Burns (1915b) says 10 

 to 11 days, but this seems in error. Only the female incubates. The 

 young remain in the nest 10 to 12 clays. Cordelia J. Stanwood MS. says 

 in her notes : "The young come from the eggs blind and limp, covered 

 with short, fine, sparse down and scarcely larger than bumblebees. 

 About the close of the second day, or the beginning of the third day, 

 they commence to open their eyes and the feather spaces begin to show 

 as dark, swollen tracts. Near the end of the sixth day, not far from 

 the beginning of the seventh, the quill stage ends, and the tips of the 

 feathers show beyond the quill casings. By the eighth day the young 

 are pretty well feathered out, and can leave the nest successfully, but, 

 if undisturbed, they usually remain in the nest until the tenth or the 

 eleventh da3^ While in the nest the young preen, stretch, yawn, beg 

 for food, and utter various calls. Both the parent birds feed the little 

 ones and cleanse the young of parasites and other vermin, although I 

 have noticed in many cases that the female bird generally seems to be 

 the one that burows under the nestlings and cleanses them and the 

 nest lining of annoying pests. * * * All these warblers that I 

 have watched caring for the young in the early stages of nest life begin 

 by feeding the little ones by regurgitation. At the same time an oc- 



