BUTEO SWAINSONI. 535 



the theory advanced by Dr. Bryant/ that the several supposed species 

 described by Mr. Cassia under the names of B. bairdi, Hoy, B. inslgnatus, 

 Cassin, and B. swainsoni, Bonap., were merely different plumages of one 

 ■ species, the very first specimens obtained by us being a family of four 

 yonng, Avitli their parents, the former being B. bairdi, while of the latter 

 the male was a very light-colored, or extremely typical, B. swainsoni, and 

 the female a very extreme example of B. insirjnatus! Similar cases were 

 often obsei-ved afterward, the plumage of the adults being sometimes re- 

 versed—that is, a male in the plumage of the so-called insignatus being 

 sometimes paired with a very light-colored female. 



The fomily mentioned above was first observed on the 2Gth of Jidy, 

 while we were hunting among the cotton-woods of the lower Truckee Valley. 

 Our attention was attracted by a peculiar squealing cry, not before heard 

 by us, and upon emerging from the A\i]lows and looking across the open 

 meadow we observed among the trees on the opposite side several largo 

 Hawks, one of which was feeding a young one in a nest in the top of a tall 

 cotton-wood. We then approached this tree under cover of the willows, 

 but upon arriving there found that the old Hawk had gone after more food 

 for its young, three of which were in the trees on the opposite side of a 

 deep and wide slough which we were unable to cross. We then shot tho 

 one in the nest, as it looked over the edge at us; but, as it did not fall, 

 found it necessary to ascend the tree, which was easily done. The nest 

 was very similar to that of other Buteones, being composed almost entirely 

 of sticks, but appeared rather small for the size of the bird, measiu-ing but 

 about two feet in diameter by one foot in thickness. We found it so filled 

 with the accumulated remains of animals carried to the young that scarcely 

 any depression was noticeable on the top, the decomposing rubbish con- 

 sisting of bones and other lemnants of small hares {Lcpm artcmisia), 

 gi-ound squirrels [Spermophilus lateralis, S. harrisi, and Ta))iias quadriviltatm), 

 and, strange to say, a full-grown young Sparrow Hawk (Fako sparveriiis). 

 We had scarcely reached the nest before the male arrived, and flying 

 about us uttered plaintive cries, of a mewing character, somewhat like the 



'"Remarks on the Variations of riuiuage of Hiitro borcalis, Auct., and ISuIco 

 hailani, AUD.*' Proc. Host. See. Nat. Uisf., VIII, 1801, pp. I(»7-lllt. 



