1887.] PROCEEDINGS OV UNITRD STATES NATIONAL MUSEUM. 553 



spots arc very fino, of i\ ])nlo delicat*^ ivddisli bnlT or lawn color, giving 

 these eggs quite a diiicreiit appearance from the others. Their varia 

 tion ill color, judging from the limited number of specimens in the col- 

 lection, seems to be fully as great as that in any of the Falconidw. 



Within the limits of the United States this species has heretofore been 

 found breeding only along the southern border of Texas, where ])r. J. 

 C. Merrill, assistant surgeon, U. S. Army, took two nests in the vicinity 

 of Fort r.rown, both containing three eggs also. These are described 

 in the l*roceedings of the U. S. National Museum, 1878, pages 1515 and 

 153. Both were ])laced in yuccas. 



NO. 342. BUTEO SWAINSONI Bonap. 

 Swaixson's JIawic. 



This species is by far the commonest hawk in the vicinity of Fort 

 Huachuca, and a resident throughout the year. Lieutenant Benson 

 found not less than forty-one of their nests containing eggs between 

 May 14 and June 18, 1887. These were all placed in low mesquite trees 

 and bushes, from 3 to 15 feet from tlie ground. Only six of these nests 

 contained three eggs each, twenty-one nests contained two eggs, the 

 remaining fourteen but a single egg. Many of the latter were un- 

 doubtedly laid by birds that had been robbed before, especially where 

 the same nest was used again, which was frequently the case, and a few 

 were uncompleted sets. Two eggs is the usual number laid by these 

 birds, in Arizona at least. The nests were bulky iilatforms, composed 

 of sticks of various sizes, with but a slight depression in the center, 

 and sparingly lined with a few bunches of dried grass. Lieutenant 

 Benson writes me, that after the Arkansas Kingbirds {Tyranniis vertica- 

 lis Qay) began to build he invariably found one of tlieii nests in any 

 tree that contained a Swainson's Hawk's nest. In one case, a i)air of 

 these birds had placed their nests directly under and but 8 or 9 inches 

 from that of the hawk. A pair of White-rumped Shrikes (Lanius luda- 

 vicianus cxcnbitoroides Swains.) built also immediately below one of 

 these hawks' nests. 



When not closely looked at, many of tiie eggs of Swainson's Hawk 

 appear to be unspotted, but on careful examination there are in reality 

 but very few that are immaculate. Out of a series of sixty-nine speci- 

 mens sent by Lieutenant Benson there are but three unspotted ones. 

 The ground-color of these eggs when fresh, is a very distinct greenish 

 white, which in course of time fades into a dull yellowish white, even 

 if the eggs are not exposed to light. They are more or less heavily 

 spotted and blotched, varying in color from burnt-umber to tawnj^ olive, 

 and in some of the lighter colored specimens from a French gray to a 

 drab-gray. Their shape ranges from a short ovate to an oval, and they 

 average about 2.23 by 1.71 inches in length and width, Tiie largest 

 egg in the series taken by Lieutenant Benson measures 2.37 by 1.76 

 inches, the smallest 1.95 by 1.60 inches. 



