24 BULLETIN 17 0, UNITED STATES NATIONAL MUSEUM 



one of three eggs, one of four eggs, and one of five eggs. Therefore 

 it is presumed that eastern nests have fewer eggs. Additional sets of 

 two eggs have been taken, even in California; but in these cases the 

 sets were incomplete or second sets. Bendire (1892) says that the 

 "eggs are laid at intervals of a day or two." 

 Tyler (1923) says: 



The eggs from any one pair of birds bear a close resemblance from year to year 

 and it is always possible to tell, by the eggs alone, when a new female takes pos- 

 session of a nest. 



I have never made a practice of taking second sets, but I have determined that a 

 second set is nearly always laid within a period of from twenty to twenty-five days 

 after the first set has been removed. Usually the same nest is used, although 

 sometimes the birds move to another site which, as a rule, is in the same cliff or in 

 one not far away. * * * Undisturbed birds raise but one brood of young each 

 season. Moreover, I am inclined to believe that certain pairs occasionally pass a 

 season without nesting, as I have, on two different occasions, found both birds 

 present at a nest site, yet their actions did not indicate that they were nesting and 

 on subsequent visits they showed no active interest in the neighborhood. 



Prairie falcon eggs are somewhat smaller than those of the duck hawk 

 and average lighter in color than the eggs of any falcon except the 

 American sparrow hawk. The eggs are very handsome and, since 

 they vary a good deal in color, are attractive to collectors. According 

 to Mr. Bent's notes they are ovate to nearly oval, finely granulated 

 to smooth, and often pimpled. The ground color is white, creamy 

 white, or pinkish white. About half the surface is finely and evenly 

 sprinkled with minute dots, nearly or quite concealing the ground 

 color; the other half is more openly spotted with larger spots that are 

 sometimes concentrated at one end; sometimes there is a broad wash 

 of color at one end, and sometimes the overlying color even obscures 

 the ground color so that the whole seems "vinaceous-cinnamon." The 

 markings are "burnt sienna", "amber-brown", "tawny", or "cinna- 

 mon." These three ground colors and the four overlying ones are 

 capable of many combinations. Since the markings also differ in 

 shape and distribution, prairie falcon eggs are subject to a wide varia- 

 tion in appearance. Very rarely an egg will show a uniform color all 

 over. One beautiful tint is a purplish shade noted by Coues (1874) 

 and by Dawson (1923) but even better described by Truesdale (1910). 



The measurements of 331 eggs, from all sections, average 52.3 by 

 40.5 millimeters; eggs showing the four extremes measuring 57.9 by 

 42.7 and 47.1 by 36.0. The largest egg came from Sweetwater County, 

 Wyo., but one only a trifle smaller was collected in the State of Wash- 

 ington. 



Young. — Bailey and Niedrach (1933) reached a nest in Colorado 

 just as the eggs were hatching. They tell us that they used a photog- 

 rapher's tent as a blind, and, although the female falcon was suspicious 

 of the blind, especially of the bright lens, she came back to her nest 



