112 



white or pale rusty ground. Wing, 6.35-G.95 ; tail, 5.50-6.30 ; culnien^ 

 0.35-0.40; tarsus, 1.85-2.05; middle toe, 1.05-1.25. 



Young female :* — Exactly like the voung male in markings and colors. 

 Wing, 7.75-8.60; tail, 6.50-7.60; ciilmen, 0.45-0.50 ; tarsus, 2.05-2.30 ; 

 middle toe, 1.30-1.50. 



To rei)resent the average style of the adult male, we select a speci- 

 men from Pennsylvania, No. 59055, IlTazareth ; L. E. Ricksecker. In 

 this example, the upper parts are a uniform plumbeous throughout, 

 the pileum being hardly appreciably darker than the back, and the tail 

 equally blue with other portions; the tail has a distinct, narrow, white, 

 terminal border ; the longer upper tail-coverts also have very narrow 

 white tips. On the lower parts (i. e., breast, sides, flanks, and abdomen), 

 the white and rufous bars are about equal in width, the latter growing 

 wider toward the shaft of tbe feathers, along which they are connected 

 by a narrow streak of rufous, the shaft itself being blackish ; the white 

 bars being thus broken into transverse oblong spots. 



There are now before us thirty examples of the adult of this species, 

 and we have examined many more ; and our conclusion is that the va- 

 riations exhibited in the plumage are purely individual, having nothing 

 to do with climatic causes, since the two darkest examples are from 

 Chiriqui, Kew Granada, and Fort Bridger, Wyoming, and the two light- 

 est-colored ones are from Guatemala and Fort Resolution, Hudson's Bay 

 Territory, while others from tbe Atlantic States are not distinguishable 

 from some obtained on the Pacific coast. As illustrating the extremes 

 of variation in the adult f>lumage, we cite the following specimens : — 



The lightest in the entire series is an adult male from Choctun, Vera 

 Paz, Guatemala (January), in the collection of Mr. Salvin. In this, the 

 upper parts are a light, decidedly bluish, plumbeous, with conspicuous 

 black shaft-streaks, exceedingly similar to the dorsal surface of adult 

 males of Falco columbarius ; the pileum is decidedly darker, with the 

 shaft-streaks less conspicuous, and the tail is decidedly more brownish 

 than the upper coverts. There is a quite distinct narrow superciliary 

 stripe of small white streaks. The general aspect of the lower parts ia 

 white, all the feathers except on the anal region and crissum with very 

 conspicuous blackish shaft-streaks, these being rendered the more 

 prominent by the faintness of the rufous markings, which are distinct 

 only along the sides, and even on the tibse are narrower than the w^hite 

 interspaces. A peculiar feature of this specimen, so far as the series 

 before us is concerned, is that the dusky bands on the inner web of the 

 primaries are broken into irregular cloudings, although they have a gen- 

 eral tendency toward transverse bands. 



A specimen from Fort Resolution, Hudson's Bay Territory, April 26 

 (No. 629, Mus. R. R.), is very similar, but the bars of the lower parts 

 are better defined, although not deeper in color, and the upper parts 

 are darker and more uniform plumbeous ; the superciliary streaks are 

 also concealed or nearly obsolete. In this specimen, as in many others, 

 the rufous bars are bordered with a narrow, dark, slaty margin. 



The darkest examples are an adult male in Mr. Salvin's collection 

 (No. 3705) from the southern slope of the volcano of Chiriqui; one 

 from Utah (Beaver, September, 24; No. 2130, Mus. R. R.); and one in 

 the National Museum, from Fort Bridger, Wyoming (No. 10759, May 26). 

 The two former are alike in their upper plumage, which is a very 

 dark plumbeous, becoming gradualy but very perceptibly darker 

 on the i)ileum, the shafts not conspicuously darker ; the longer upper 



* Iris sulphur-yellow ; tarsi aud toes rich lemon-yellow. (Fresh colors of No. 53"204.) 



