28 BULLETIN 17 0, UNITED STATES NATIONAL MUSEUM 



of the natural dark color. She hovered overhead, shrieking her displeasure at 

 the invasion, and, even at that distance, her black eyes contrasted with her light- 

 colored feathers. Niedrach has known that particular bird for nine years. She 

 had nested in the vicinity each year, but he had never been able to reach her nest 

 to photograph it, and, in that time, he had never seen other light-colored falcons, 

 with the exception of one young bird, which had a white feather in the center of 

 the back. Apparently, the young were usually of normal plumage. [PI. 10.] 



Like most hawks, the adult prairie falcons may exhibit either light 

 or dark phases of plumage, with all gradations between the two 

 extremes. Although it is probable that this species molts at least 

 once a year, nothing is known about the time or the manner. Neither 

 is it known positively whether there is only one molt each year or more. 



Food. — While I was examining reports on the food habits of this 

 falcon, from various sections of its wide range, two things became 

 very evident: First, no adequate study of the subject has ever been 

 made, and we are therefore mostly dependent upon various items 

 picked up incidental to oological, or other, studies; and second, these 

 incidental notes show great diversity of food, possibly due to differ- 

 ence in range, availability of certain victims, opportunities of the 

 observer, and changing conditions as affected by man. All agree 

 that this falcon is bold and enterprising and fully capable of easily 

 killing prey even larger than itself. No doubt the ease and certainty 

 of securing a stated prey are responsible for a seeming preference for 

 that prey in that locality; otherwise, food is normally quite varied. 



In places where there are large flocks of these small birds, the prairie 

 falcon preys on sparrows and Brewer's blackbirds, more or less harry- 

 ing the flocks as long as they remain in the vicinity. Its powers of 

 flight are great enough to permit of the successful chase and capture 

 of mourning doves; and in places it takes meadowlarks in numbers. 

 Speaking of central California, Tyler (1923) says: "My personal 

 observations have convinced me that small birds are preferred at all 

 times * * *. From the time the falcons return to their nest 

 cliffs in early spring through the egg laying and incubation periods 

 the Gambel Sparrows (Zonotrichia leucophrys gambeli) are very 

 abundant in the regions where falcons abound and a very heavy toll 

 of sparrows is taken. But, by the time the young falcons have 

 appeared, these sparrow hosts have practically all migrated and the 

 falcon turns his attention to Western Meadowlarks, Valley Quail, 

 and Western Mourning Doves." Most of the falcon's hunting is 

 done early in the morning and late in the afternoon, even in cloudy 

 or comparatively cool weather. Dawson (1923) says: 



The bird makes little fuss over the capture of small game. It simply material- 

 izes out of the empty blue and picks up a gopher or a blackbird as quietly as you 

 would pluck a flower. The approach has doubtless been nicely calculated. The 

 thunderbolt, launched from the height of half a mile, has been checked every few 

 hundred feet by a slight opening of the wings, that the Falcon might gauge the 



