240 NORTH AMERICAN BIRDS. 



after making the first critical examination of the series at my command, was, 

 that tlie coarsely mottled specimens were confined to the east, and that those 

 finely mottled beneatli were peculiar to the west ; and this view I am not 

 yet prepared to yield. I have never seen an adult bird from any western 

 locality which agrees with the eastern ones described above ; all partake 

 of the same characters as those described, in being finely and faintly mottled 

 beneath, with sharp black shaft-streaks, producing the effect of a nearly 

 uniform bluish ground, the black streaks in conspicuous contrast, the tail- 

 bands nearly obsolete, etc. But occasional, not to say frequent, individuals 

 obtained in the eastern States, which agree in these respects with the western 

 style, rather disfavor the view tliat these differences are regional, unless we 

 consider that these troublesome individuals, being, of course, winter migrants, 

 have strayed eastward from the countries where they were bred. The 

 Colorado female described above exhibits a rather suspicious feature in hav- 

 ing a single feather, on the lower parts, which is coarsely barred, as in the 

 eastern style, while all the rest are finely waved and marbled as in the 

 western. If this would suggest that the differences supposed to be climatic 

 or geographical are in reality only dependent on age, it would also indicate 

 that the finely mottled individuals are the older ones. 



If future investigations should substantiate tliis suggestion as to tlie 

 existence of an eastern and a western race of Gosliawk in North America, 

 they would be distinguished by the following characters : — 



Yar. atricapillus. Adult. Markings of the lower surface coarse and 

 ragged ; feathers of the pectoral region with broad nriedial longitudinal 

 streaks of the same slaty tint as the transverse bars, and with only the shafts 

 black. Tail-bands distinct. Young. Pale ochraceous markings prevailing 

 in extent over the darker (clear grayish-umber) spotting. Stripes beneath 

 narrow, clear brownish ; those on the flanks linear. Wing, 12.2.5 - 14.25; 

 tail, 10.00 - 12.75 ; culmen, .80- 1.00 ; tarsus, 2.90 - 3.15 : middle toe, 1.70- 

 1.95. ILih. Eastern region of North America. 



Yar. striatulus. Adult. Markings of the lower parts fine and delicate, 

 and so dense as to present the appearance of a nearly uniform l)luish-ashy 

 surface ; feathers of the pectoral region without the medial stripes of 

 slaty, but with broad shaft-sti'eaks of deep black, contrasting very con- 

 spicuously with the finely mottled general surface. Tail-bands obsolete. 

 Young. Darker (brownish-black) markings prevailing in extent over the 

 lighter (nearly clear white) ones. Stripes beneath broad, brownish-black ; 

 those on the flanks cordate and transverse. Wing, 12. 00 - 1.3.(30 ; tail, 9..50- 

 12.20; culmen, .85-1.00; tarsus, 2.70- 3.15 ; middle toe, 1.70 -.185. Hab. 

 Western region of North America. 



LIST OF SPECIMENS EXAMINED. 



Yar. atricapillus. 



National Museum, 8 ; Philadelphia Academy, 7 ; New York Museum, 3 ; Boston 

 Society, 2 ; Gr. N. Lawrence, 4 ; W. S. Brewer, 2 ; Museum, Cambridge, 2 ; R. Ridgway, 

 2. Total. 30. 



