OLIVE-BACKED THRUSH 179 



There is a set in my collection from Estes Park, Colo., that came 

 from a nest that was placed near the base of a small bunch of willows 

 on a meadow near a stream. And the nests found by Mr. Swarth 

 (1922) in the Stikine River region, British Columbia, were all at the 

 lower levels in willows or alders. Dr. Paul Harrington writes to me 

 that, in central Ontario, he has found the nest in balsam, hemlock, 

 tamarack, spruce (black and white), cedar, top of a stump, and 

 rarely in a deciduous tree. One was 30 feet up in a birch. 



Eggs. — The set of eggs laid by the olive-backed thrush varies from 

 three to five; sets of five are apparently rare, and sets of three seem 

 to be about as common as those of four. The eggs are usually ovate 

 in shape, with occasional variation toward elongated-ovate or rounded- 

 ovate, and they have very little gloss. The ground color varies from 

 "Nile blue" to "pale Nile blue" or even lighter. They are generally 

 more or less evenly marked with spots, small blotches, or fine dots of 

 light browns, "hazel" to "cinnamon," or paler yellowish brown. 

 Some are heavily marked about the larger end, and some are very 

 sparingly marked with very pale brown; very rarely an egg appears 

 to be nearly immaculate. The measurements of 40 eggs in the United 

 States National Museum average 22.4 by 16.5 millimeters; the eggs 

 showing the four extremes measure 26.7 by 18.3, 25.7 by 18.6, 20.3 

 by 16.3, and 22.9 by 14.7 millimeters. 



Young. — Miss Stanwood made some extensive and intimate studies 

 of the nest life of olive-backed thrushes in several different nests and 

 says in her notes: "I found the eggs hatching in 1908 on the twelfth 

 and thirteenth days, and in 1913 on the tenth, eleventh, and twelfth 

 days from the beginning of the incubation period. The young mature 

 sufficiently to leave the nest in from 10 to 12 days. The mother 

 olive-backed thrush appeared both to incubate the eggs and to brood 

 the young. For the first few days after the babes were hatched she 

 left the nest only for very brief periods; during this time she brooded 

 the young and moved back onto the rim of the nest every few minutes 

 to feed the youngsters digested food and cleanse the nest. She fed 

 each nestling, in the beginning, every time she cared for them; stand- 

 ing astride the little ones, she dealt with one sturdy individual at a 

 time; she pecked him and touched him with her beak until he held 

 his head up and begged lustily for food. She also burrowed under 

 the young to remove all parasites from the nest and from the sensitive 

 bodies of the bantlings. Frequently she ministered to the babes as 

 often as once in four minutes. When brooding she changed her posi- 

 tion on the nest frequently, to accommodate herself to the wriggling 

 young, shielding them with her body from the hot sun and the cold 

 rain. Both the male and the female fed the bantlings fresh insect 



