44 AN ECONOMIC STUDY OF FIELD MICE. 
The most common Old- World representative of the genus is Buteo 
buteo, the common buzzard of England, and popularly known in 
Germany as the mouse buzzard (Mdusebussard). That the last name 
is well deserved, is shown from the researches of Dr. G. Rorig, of 
Berlin, who in 784 stomachs of this species found no les> than 1.124 
rodents, of which 1,057 were the common field mouse (J/, arvalis).* 
Two prominent species of rough-legged hawks (Archibuteo) occur 
in America. Both arc winter sojourners with us. The northern form, 
the common rough-leg (Archibuteo lagopus sancti-johannis) , sum- 
mers north of the United States. The ferruginous rough-leg (A. fci'- 
rugineus), commonly known as the squirrel hawk, nests extensively 
in the Western States, but is more common there in winter. Both 
species are large and ma} r be easily distinguished by the feathering of 
the legs, which extends to the base of the toes. Doctor Fisher ex- 
amined 50 stomachs, all but 1 being of the common rough-leg. Of 
these. 40 contained mice only: 5, other mammals: 1, insects and a 
lizard : and 4 were empty. Of the 40 containing mice, 28 had meadow 
mice only, the number varying from 1 to 8 and the average being 
more than 3 to each hawk. These are winter records. In summer 
the birds doubtless are largely insectivorous. It is certain that the 
rough-legs do not often molest wild birds or domestic fowls. 
The researches' of Doctor Rorig make an equally favorable show- 
ing for the Old World rough-legged hawk (Archibuteo Jag opus lago\ 
pus). He examined 250 stomachs of that species and found remains 
of 879 rodents, mostly field mice. Xinet}^-four per cent of the birds 
examined by him had eaten injurious rodents. 6 
The true falcons (genus Falco) of North America comprise 17 
species and subspecies, of which 3 are accidental visitors from abroad, 
and several others, notably the gyrfalcons, are exceedingly rare within 
the United States. The various falcons differ much in size, but all 
are strong and swift of wing. The larger species destroy poultry and 
game, while the smaller kinds prey upon small birds and insects. All 
feed to some extent upon mice. The most common species are the 
duck hawk (Falco. peregrinus anatum), the prairie falcon (Falco 
mexicanus), the pigeon hawk (Falco columbarius) , and the sparrow 
hawk (Falco sparverius) . 
The duck hawk is a rather large falcon, and, as its name implies, 
preys much upon waterfowl. It destroys also game birds, domestic 
fowls, pigeons, and small birds. Although it feeds to some extent 
also upon insects and mice, the habits of the species, on the whole, 
do not commend it to the protection of farmers and sportsmen. 
" Arl>. Biol. Abteilung fur Land- und Forstwirtschaft, IV Band. 1 Heft, 
p. 64, 1903. 
'Ail>. Biol. Abteilung fur Land- und Forstwirtschaft, IV Band, 1 Heft, p. 74, 
1903. 
