1907] Beebe: Geographic Variation in Birds. 19 



of 1903 it moulted well, and although, when compared with skins 

 of typical H. mustelina, the breast spots seemed larger and 

 darker, yet there was too little difference to be considered, under 

 ordinary circumstances, as more than individual variation. The 

 death of the bird occurred on August 20, 1904, when its moult 

 was not yet completed. Many of the feathers, however, are full- 

 grown, and the remarkable change in amount of color which has 

 taken place is perfectly apparent. (Fig. 2.) 



The upper parts are but little changed, the rufous being 

 slightly dulled by the olive tinge which extends as far as the 

 nape. The most radical difference is to be observed in the feath- 

 ers of the breast and sides. The general aspect of these parts 

 is of a brownish black, variegated with narrow light edges to 

 the feathers. On the breast the white is more apparent, some 

 of the feathers having circular spots of normal size ; but on the 

 sides, flanks and under tail coverts, and even in the center of the 

 belly, the black areas are almost confluent as the feathers lie 

 naturally. The primaries and rectrices show a very pronounced 

 lack of pigment — a tendency toward albinism which is unique 

 among my experiments — albinism having in no other case re- 

 sulted from a prolonged exposure to excessive humidity. 



The third specimen of H. mustelina, which was taken from 

 the same nest as the other two, is alive to-day, and in every detail 

 is in perfectly normal plumage, having been caged with a number 

 of other thrushes, outdoors in summer and during cold weather 

 in the passerine hall of the large bird house. The food of both 

 thrushes was the same, a mixture somewhat resembling the 

 "mockingbird food" of dealers — a little scraped raw meat and 

 earthworms; meal worms once a week, fruit, lettuce, chickweed 

 and many kinds of berries. 



In a natural state, wood thrushes do not show a great deal 

 of variation, although in some specimens the pectoral spots are 

 more numerous and larger than in others. This is said to be 

 especially true of birds from Guatemala, and in an individual 

 from the State of Tabasco, South Mexico, it was so pronounced 

 that Bonaparte, in 1853, described it as a separate species under 

 the name of Turdus densus. This shows that, among wild birds 

 of this species, there is at least a slight tendency toward melan- 

 ism under the effects of warmth and humidity. 



Zonotrichia albicolUs (Gmel.), White-throated Sparrow. — 

 On the second day of October, 1901, two white-throated sparrows 

 were trapped in the Zoological Park in traps set for English 

 sparrows. They were both, as was eventually determined, males, 

 and, judging from the dullness of the plumage, were young birds 



