PALMER'S THRASHER 393 



unlikely that a third nesting would be attempted, unless one of the 

 earlier attempts had been broken up. 



A. L. Rand (1941) has published a most interesting and very ex- 

 tensive paper based on his studies, near Tucson, Ariz., of a large 

 number of young thrashers of this species, both in the wild and in 

 captivity, from the time of hatching until about 90 or 96 days old. 

 The reader is referred to this paper for details, as only a few of 

 the many interesting facts and reactions can be mentioned in the 

 limited space available here. He says that "in common with most 

 passerine birds the young thrasher hatches in a blind, nearly naked 

 condition; has a tendency to keep right side up and open its mouth 

 for food in response to a wide variety of stimuli ; it is utterly depend- 

 ent on the adult. In the course of 5 or 6 weeks its physical equipment 

 and its behavior develop so that it can survive independently, finding 

 its own food and escaping its enemies." 



He gives a detailed account, day by day, of the physical growth 

 and the development of behavior of the young bird during the 18 

 days that it is in the nest. For the first 5 days the young are blind 

 and helpless. On the sixth day, the eyes can be widely opened and 

 the contour feathers are just breaking the skin; the rectrices are 

 beginning to break out of their sheaths. On the fourteenth day 

 the young bird is well feathered, and may leave the nest on or before 

 the eighteenth day. "Two young of one nest, usually one a day 

 older than the other, often leave the nest a day apart, the stimulus 

 causing one young to leave not causing the other to do so. Their 

 physical equipment is such that they can hop and run well, but their 

 wings only help them to flutter down at a steep angle. * * * When 

 young thrashers in captivity were beginning to feed themselves to 

 a considerable extent (after about 30 days), they still begged occa- 

 sionally. * * * By the 40th day they became completely inde- 

 pendent and somewhat shy of persons." 



He conducted a number of interesting experiments to determine the 

 reaction of young thrashers to various stimuli, including mnnimals, 

 predatory birds, and reptiles introduced in the cages. The thrashers 

 usually showed mild interest and sometimes fled, but they apparently 

 had not learned to recognize dangerous enemies. This section of his 

 paper is well worth reading. 



Plmnages. — The Brewster collection, in the Museum of Comparative 

 Zoology in Cambridge, contains a large series of specimens of this 

 thrasher, including several in juvenal plumage. I cannot improve 

 on Mr. Brewster's (1882a) own words in describing some of them. 

 One young bird, "although well feathered, has the wings and tail un- 

 developed, and was taken from the nest. Its entire upper plumage 

 is rusty brown with a chestnut tinge which deepens on the rump 



