FALCOSTIDJS. — BUTEO SWAINSONI. 



25 



been found to lia^e prevailed among our ornithologists in regard to the lines of sepa- 

 ration between this and two other North American Hawks, elsewhere referred to more 

 ■ at length, there would be no doubt, in my mind, that this paternity was unquestion- 

 able. As it is, I am of the opinion that it is probably rightly named. I take only the 

 precaution of stating that it is barely possible Dr. Heermann may have mistaken a 

 different hawk for a B. sivainsoni, and that it maybe found to belong to another bird. 

 This egg differs materially from those of B. montanus, is more pointed at the smaller 

 end, and is of a somewhat less capacity. The ground color is a bluish-white, and the 

 egg is marked at one end with blotches and spottings of a light sepia-brown. Its 

 measurements are 2-A inches in length, by lyf in breadth. According to Sir John 

 Richardson (Fauna Boreali Americana, II, 4), the B. sivainsoni arrives in the fur 

 countries in the middle of April, and soon afterwards begins to build its nest on a 

 tree, of short sticks, lining it sparingly with deer's hair. The eggs, from three to five 

 in number, are equal in size to those of the domestic fowl, and have a greenish- white 

 color, with a few large dark-brown blotches at the thick end. The one described 

 above was spotted at the smaller end, an accidental but by no means uncommon 

 occurrence in the eggs of many species. , 



The geographical distribution of this Hawk can as yet hardly be regarded as 

 having been well determined. Thus far the only specimens brought home by recent' 

 collectors have been from the region between the Yellowstone River and the Great 

 Salt Lake, and southward, along the eastern slope of the Rocky Mountams, to the 

 Staked Plains of Texas. None have been found thus far on the Pacific coast, or 

 east of the Mississippi River. Dr. Heermann's specimen, if really the present species, 

 will extend this range to the w^estward. 



The egg represented in the plate was taken by Dr. James Trudeau near Saline, 

 Arkansas, who assured me that he identified it with its parent. It differs from Dr. 

 Heermann's specimen in size, and in the absence of distinct spottings. It varies also 

 from the descriptions gi-\-en of the egg by Richardson and Swainson. 



I have also a drawing of an egg taken by Dr. Trudeau in Western Louisiana, and 

 supposed by him to be an egg of this HaAvk. They present no unusual variations, 

 the prmcipal being in the depth of the secondary coloring. They are each of an 

 extremely well marked o^al shape, approaching a spheroidal. The Arkansas egg 

 measures 2-r6 inches in length by IH inches in breadth. The measurement of that 

 from Louisiana is 2A inches by Itt, being a little more oblong and less spheroidal. 

 The ground color of both is white, and each is sparingly spotted and blotched with 

 markings of light umber-brown and a purplish-slate. In the specimen from Saline, 

 these markings are fainter, and the shades of color less distinctly traced. 



Since the above was prepared for publication, I have recei'^-ed from Mr. Krider of 

 Philadelphia an egg of the B. sivainsoni, which I have substituted in the plate for 

 the egg given me by Dr. Trudeau, and mentioned above. It was obtained by Dr. 

 Heermann, in California, and by his permission was forwarded at the last moment 

 in which it could be made available for the present work. Its size is almost ex- 

 actly that of the one from Saline ; its shape and general appearance are the same, 

 except that it is more distinctly marked Avith secondary colors. This egg may be 

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