EXTRACTS FROM THE FOREIGN PERIODICALS. 
271 
Other birds only migrate occasionally and partially, according to the supply 
of food. The Virginian Partridge, if grain is scarce in New Jersey, 
crosses the Delaware to proceed to Pensylvania. The flight of these 
birds is so heavy, that, in general, unable to cross the river, they fall into the 
water, and complete the journey by swimming. It is the same with the Wild 
Turkeys, which, when they arrive weary and lean on the other side the Ohio^ 
the Missouri, or the Mississipi, are caught in great numbers. 
It is supposed that the Migratory Pigeons only visit the U. S. in very hard 
winters. This appears, however, to be erroneous. I have seen immense flights 
of these birds in Canada in winter, during intense cold, but after a season highly 
favourable to the grain on which they subsist. It is only the want of this food 
which compels them to migrate to the south. 
Agricultural improvements, by introducing plantSj &c., extend the migrations 
of birds. Thus the Mocking Wren f Troglodytes Ludovicianus)^ and other species 
now common in the northern states, were unknown in the time of Wilson, 
The Cliff Swallow (H. lunifrons'), a Mexican bird, appeared for the first time 
on the banks of the Ohio, in 1815. It excited great interest by the structure of 
its mud-built nest, of which several are placed together, and resemble, in shape 
a group of Gourds. Every year it advances in its migrations, which now extend 
to Canada. The same may be said of many other birds. 
It has been computed, that out of the 450 species known in North America, 
only 108 are common to the two continents, the water-birds forming more than 
three-fifths of the number. These species are principally Eagles, Hawks, Owls, 
and Crows, among land bird^, and Ducks or sea-birds among the Aquaticce. 
The most singular notions have been entertained respecting the habits of the 
Rail. Absent throughout the summer, it suddenly appears in myriads in Au¬ 
gust, on the banks of the Delaware. Here they remain till October, when they 
suddenly disappear, and not one is to be seen where, on the day before, thej 
were found by hundreds. As their flight is heavy, these birds are supposed to 
retire in winter to hollow places, or even under the ice. The fact is that they 
take their departure in the night. They breed very far north, and have been 
seen on their nests along the marshy lakes of Upper Carolina. 
When the period of departure arrives, birds display a kind of irresistible rest¬ 
lessness. Goldwings, Orioles, &c,, carried whije young to the north, and 
liberated in spring, fly in the direction of the pole, as if guided by a compass. A 
little before the approach of winter, and sometimes when the cold weather is 
already commencing, birds of passage assemble in flocks. The young of most 
species unite, as if they disdained to inquire the way of their elders. Some fly 
separate, others in thin scattered troops, and others again in regular flocks. 
Some fly slowly, and as though affected by the cold; others proceed rapidly, and 
achieve their journey in a few daj^s. Some birds fly from land to land, and often 
