216 LIFE HISTORIES OF NORTH AMERICAN BIRDS. 



the cottonwood and a few dry leaves. It was fully 30 inches in diameter 

 on top and 20 inches deep outside. In southern Colorado and northwestern 

 Texas tliev nest occasionally on cliffs and the sides of perpendicular bluffs. 

 Mr. William Lloyd presented a fine set of three eggs of this species to the 

 U. S. National Museum collection, taken from the side of a chalk 1)1 uff, about 

 75 feet from the bottom and 20 feet from the top of the bluff, on April 2, 1890, 

 in Presidio County, Texas. Such sites are probably selected on account 

 of the absence of suitable trees. 



I believe they rarely build a new nest in the West, the old ones being 

 generally repaired by the addition of a little fresh material. The fibrous 

 bark of the redwood is often used for lining when obtainable, and the fine 

 inner bark of the cottonwood likewise. 



In western Texas the same nest has occasionally done duty for two 

 different species of Raptores, the Western Horned Owls using it in January 

 and February, and the Red-tails subsequently. 



But a single brood is raised in a season; a second and sometimes a, third 

 set of eggs is laid, however, should the first be taken or destroyed. The 

 usual number of eggs is two or three, sets of one or four being rarely found. 

 I have, however, found the Western Red-tail incubating a single egg in which 

 the embryo was well advanced and where the birds had not, been previously 

 disturbed, and also found a set of four, near Fort Lapwai, Idaho, in the 

 spring of 1871. 



Mr. Charles H. Townsend took another set of four near Red Bluff, 

 California, in April, 1884. The nest from which these eggs were taken was 

 placed in a scrubby oak, about 20 feet from the ground. It was biiilt of 

 heavy twigs and had a uniform lining of soap root fiber. 1 



Incubation lasts about four weeks, and the eggs are deposited at intervals 

 of a couple of days. There is no marked difference in the size, shape, and 

 color of these eggs as compared with those of the common Red-tailed Hawk, 

 and they are practically indistinguishable from each other; but among those 

 before me the proportion of spotted ones is larger than in the former, very 

 few being entirely unmarked. The average measurement of thirty-six eggs 

 of the Western Red-tail is 59 by 46.5 millimetres. The largest egg of the 

 series measures 66 by 46.5, the smallest 53.5 by 44 millimetres. 



The type specimens selected show the more heavily marked styles. No. 

 20745 (PI. 6, Fig. 7), from a set of three in the Bendire collection, was taken 

 by the writer near Camp Harney, Oregon, May 29, 1877, and incubation 

 was far advanced when found. It shows a considerable amount of the laven- 

 der and ecru-drab shell marking, not commonly found among the eggs of the 

 Red-tailed Hawks. No. 20763 (PI. 6, Fig. 8), from a set of two, Bendire col- 

 lection, is the darkest colored egg of the entire series. The ground color in 

 this specimen is a rather light fawn, while in the other it is of the normal 

 tint, It was taken by myself from a nest in an oak tree near Camp Critten- 

 den, Arixona, April 29, 1X72. 



'Proceedings U. S. National Museum, 1887, Vol. x, \t. 202. 



