296 NOTES ON THE FAUNA 
saw also species of Vireo, (Pipilo arcticus?), Dendroica œs- 
tiva, Colaptes (duratus?), Geothypis trichas, and Certhia 
Americana, which, probably, had nests near there. The 
locality is about fifty miles by the river west of Fort Union. 
The absence of shrubbery, except close to the river, con- 
fines most of the small birds to a narrow range, and makes 
it easy to find their nests, none of the trees being large. It 
will be noticed that at least two species peculiar to the west- 
ern half of the continent breed so far east, and it is possible 
that the Empidonax, Pipilo and Colaptes, were also of the 
western types. The rocky bluffs which border the river 
above the Great Bend, and are often high enough to appear 
like mountains, although only the escarpment of the Great 
Plains, apparently favor an extension eastward of the Moun- 
tain fauna to this point ; the Mountain Sheep ( Ovis montana), 
Woodrat (Neotoma cinerea), and perhaps other mammals 
coming down in company with the birds, etc. At the same 
time it is remarkable that all the eastern birds mentioned 
extend in this latitude entirely across the Rocky Mountains, 
though most of them do not even reach the mountains north- 
ward, and seem, therefore, to follow the Missouri River 
westward, in their spring migrations. 
On June 22nd I obtained eggs of the Brown Thrush ( Har- 
porhynchus rufus) which is common to the Rocky Moun- 
tains. I noticed some species of Swift (Cheetura ?) with & 
white throat, but too high to shoot. We reached the north. 
of Milk River, where large herds of buffalo were passing 
towards the South, very few having been seen below that 
point. That pretty and musical bind o£ the high plains; 
m the Lark Bunting ( Calamospiza bicolor), also oodd near 
=, Shere, and s utenda east to Fort Union. : 
e : The bluffs from Milk River to Fort Benton are higher and : 
/. more rugged, with groves of coniferous and other trees 8f 
. intervals, being spurs of the Black Hills, which form the 
i first range of the Rocky Mountains. I had little oppor- - 
x for col ig along this interesting portion ef tbe. 









