170 
BIRDS OF NEW MEXICO 
These fall flocks which collect soon after the breeding season in the 
foothills and on the plains sometimes contain hundreds of individuals 
and feed almost exclusively on grasshoppers and crickets. For a flock 
of three hundred hawks, Doctor Fisher estimates 900,000 grasshoppers 
destroyed in a month, with a saving to the ranchman of thirty tons of 
produce; and this estimate he considers too low by half. As he asks, 
“what estimate can be placed on the services of the hundreds of thou¬ 
sands which are engaged in the same work for months at a time?” 
And yet, one of the western States put a bounty on hawks and owls and 
“thousands of grasshopper eating hawks were destroyed at the public 
expense!” (1907, p. 88). Still we complain of the destructive work of 
insects! 
In Montana Mr. Cameron’s ranch was visited in April, 1890, by a 
migrating flock of about two thousand Swainson Hawks. They filled 
the trees and sat in rows on the ground among the cattle. But on the 
following morning they “had vanished as completely as the Assyrian 
host” (1907, pp. 262-263). 
On one of the autumnal migrations of hawks of various kinds, an ex¬ 
traordinary flight was witnessed by H. S. and H. B. Forbes, over Mount 
Monadnock, N. H. Thirty or forty gathered, “swooping, turning, and 
soaring upwards in irregular steep spirals . . . until the specks resem¬ 
bled a swarm of large insects, black against the pearl-gray clouds . . . 
Finally the whole flight had spiralled upward into the cloud mass and 
was lost to view.” The height of the clouds—with Mount Wash¬ 
ington for scale—was estimated as about 7,000 feet. As the flock had 
circled upwards, it had moved in a southerly direction, and “it seems 
probable” that the migrating band “found it advantageous to rise above 
the cloud curtain” (Auk, 1927, pp. 101-102). 
In winter after the insects had disappeared, great numbers of Swain¬ 
son, Marsh, and Ferruginous Rough-legs found by Mr. Ligon between 
the San Simon Ranch and Carlsbad were “apparently contentedly 
wintering where rats and rabbits were so abundant” (MS). It has 
been estimated that the Swainson “saves western farmers $117,000 
annually by the destruction of grasshoppers and field mice” (Forbush). 
Additional Literature.—Sharp, C. S., Condor, IV, 116-118, 1902. 
AMERICAN ROUGH-LEGGED HAWK: Triorchis lagopus s&ncti-johannis 
(Gmelin) 
Plate 9 
Description. — Male: Length about 19.5-22 inches, wing 15.7-16.8, tail 9-10 
bill 1.3-1.4. Female: Length about 21.5-23.5 inches, wing 16.1-18, tail 9-11 
Like Buteo but bill small and weak and leg feathered down to toes: wing with four 
quills cut out on inner webs. Adults , normal phase: Upperparts brown, marked 
with white, rusty and yellowish brown; tail white at base, barred beyond, and with 
dusky terminal band; wing quills tipped with black, wing linings blackish making 
