288 S WA INS ON- S HA WK. 



Light stage. 



Coi,on. Adult male. Above, dark-brnwn everywhere, lightest on the head, becoming darl<er on the vpings and ashy 

 on the tail, witli tlie feathers inoreor less edge.1 with rufous, especially on the neck. The wings are obscurely harred with, 

 dusky and the tail is tipped with vrhitish and is en ssed with about twelve wavy lines of dusky. Concealed patch on oc- 

 ciput, white. Sides and base of upper tail coverts, white, harred with rufous and sooty-brown. Bentat!!, everywhere,, 

 white, pure on the throat but tinged on the remaining under portions with yellowish-rufous, while the breast is banded 

 wic!i reddish-brown, which has an ashy ovei-washing, but every feather of tins portion is streaked in the centre with dark- 

 brown. The sides, flanks, and under tail coverts, are barred with rufous. There is a spot of black on the tijis of the un- 

 der wing coverts. 



Adult female. Much darker above than the above described and t^ie lower portions are strongly tinged with ruf lus,, 

 barred with a deeper shade of the same coU:r. The flanks are barred acd streaked with dark-brown. Olhtrvvife as in 

 the male. 



Young. Quite similar to the adult above but mucli more decidedly rufjus, and the outer webs of primaries and tail 

 are edged with ashy. Behjw, yellowish-rufous, tinged with ashy, thickly marked vvitli drop-shaped spots of brown which 

 crowd together on the breast so as ti.> form a b.md. The flank-; are also barred with dusky. 



D.^RK ST.\GE. 



Color. Adult. The throat, under wing and under tail coverts are as in the light stage but the remaining portions 

 are very dark-brown, cr nearly black, but tlie bandings on the wings and tail are as described. There are occasionally 

 rufous markings Itelow, especially in the female. 



Young. Very dark, but showing strong traces of rufous on both surfaces. Bill and iris, brown, cere, greenish, and 

 feet, yellow, in all stages. 



OBSERVATIONS. 



The young is the "Bairdi" of authors, while the dark type is '^insignatus^^. There is considerable variation in plum- 

 age, for specimens occur in all gradations between the light and dark stages; but this species may be recognized by the 

 white throat, incision of but three outer quills, combined with the size and colors as described. Distributed througliout 

 Western North America. Bare in Illinois and accidental in Canada and JIassachusetts. 



DIMENSIONS. 



Average measurements of male specimens from Western North America. Length, 10'55; stretch, 47'S5; wing, 15'25; 

 tail, 7'00; bill, '82; tarsus, 2'52. Longest specimen, 20'63; greatest extent of wing, 48 50; longest wing, 15 50; tail, 8'50; 

 bill, '85; t.-rsus, 2'60. Shortest specimen, 18 75; smallest extent of wing, 47'25; shortest wing, IS'OC: tail, 7 50; bill, '80; 

 laisus, 2'45. 



Average measurement^ of female specimens from AVestern North America. Length, 20"25; stretch, 49'23; wing, 1000; 

 tail, 8'50; bill, '9'); tarsus, 2'60. Longest specimen, 21'.W; gr.i^atest extent of wing, 5100; longe-t wing, lti'50; tail, 9'32; 

 bill, 100; lar.sus, 2-70. Shortest specimen, 18'8o; smallest extent of wing, 47-00; shortest wing, 15-50; tail, 8-25; bill, -85; 

 t:irsus,2-.'')0. 



DESCRIPTION OF NESTS AND EGGS. 



Nests, placed in trees or bushes; they are quite bulky structures, composed of sticks and twigs, arranged in a com 

 pact manner. 



Eggs, four to six in number, vaiying from spherical to oval in form, yellowish-white in color, spotted and blotched irreg- 

 ularly and rather faintly with reddish-brown, with occasional markings of purplish. Dimensions from r75x2-30 t<:) 1-82 

 x2 32. 



HABITS. 

 The first reconl of the occurrence of this species east of the Mississippi, was made from 

 a specimen taken in the vicinity of Montreal, Canada, about the year, 1854, nothing more 

 being hetird of it in this section until one was obtained in Salem, Massachusetts, in 1873. 

 Then Mr. E. W. Nelson found them breeding on Fox Prairie, Illinois, in 1875 and obtained 

 four specimens, and Mr. William Brewster makes record of a specimen which w;is ttiken 

 at Wayland, Massachusetts, in September, 1876. Thus we are obliged to give Swtiinson's 

 Hawk a permanent place in our fauna, although it is yet very rare east of the Mississippi. 



