192 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



measurements of 50 eggs in the United States National Museum 

 average 23.0 by 17.0 millimeters; the eggs showing the four extremes 

 measure 24.9 by 16.0, 23.9 by 19.8, 20.6 by 16.8, and 22.4 by 15.8 

 millimeters. 



Plumages. — The natal down of the gray-cheeked thrush does not 

 seem to have been described. Dr. Dwight (1900) describes the 

 juvenal plumage of an Alaskan specimen, as follows: "Above, greenish 

 olive-brown, wings and tail darker, the pileum, back, wing coverts 

 (except primary and greater) and rump with buffy white linear shaft 

 streaks. Below, white, very faintly tinged with pale buff on the 

 breast and sides, the breast and throat spotted with black, tending to 

 barring on forepart of abdomen and flanks. Sides of head pale buff, 

 black spotted; submalar streaks black; distinct orbital ring rich buff. 

 * * * This dress is grayer and with less buff than the correspond- 

 ing plumage of T. u. swainsonii." 



The first winter plumage is acquired by a partial postjuvenal molt, 

 which involves the body plumage and the lesser wing coverts, but not 

 the greater wing coverts, or the rest of the wings, or the tail. Dr. 

 Dwight (1900) describes this plumage as "above, similar to corre- 

 sponding plumage of T. u. swainsonii, the olive-brown usually darker 

 with less yellowish tinge, especially on the head. Below, with no buff 

 except a faint wash on the jugulum; the sides of the head and breast 

 are therefore much grayer and the orbital ring distinctly white. The 

 buffy edgings or terminal spots of the retained juvenal wing coverts 

 are usually distinctive of the first winter dress." The postjuvenal 

 molt of young birds and the postnuptial complete molt of adults are 

 both, apparently, accomplished in August before migration. There 

 is evidently no molt in spring, but wear and fading produce a slightly 

 grayer effect. The sexes are alike in all plumages. 



Dr. Wallace (1939) writes: "Breeding birds of the Newfoundland 

 type vary from Brownish Olive, which is the migration color of 

 aliciae, to Olive-Brown or Sepia. Thus they differ from summer 

 specimens of the continental form by the almost complete lack of 

 grayish suffusion in the dorsal plumage, the gray being replaced by 

 brownish hues. Below, they are similar to the northern gray-cheeks, 

 but with more buffy appearance on the throat and breast." 



Food. — Professor Beal (1915b) examined the stomachs of 111 

 gray-cheeked and BicknelFs thrushes, combining the two subspecies. 

 The analysis showed 74.86 percent of animal matter and 25.14 per- 

 cent of vegetable food. Beetles were the largest item in the former, 

 33.32 percent; but only 2.83 percent were the useful Carabidae; the 

 remainder belonged to harmful families, such as the Scarabaeidae, 

 Elateridae, and the weevils. Ants amounted to 16.34 percent, and 

 other Hymenoptera, as wasps and bees, were eaten to the extent of 



