THE PRESIDENTIAL ADDRESS.
11
Carrier Pigeon returns hundreds of miles to its dovecot only in
search of food. With the migrant as with the trained carrier there
is a homing influence somewhere.
The migrating flocks of the American Passenger Pigeon (Ecto-
pistes Migratorius), a species which is said to have occurred in
Britain three or four times, are immense. Wilson gives the following
statistics of a great flight he met with in Kentucky : "If I only esti-
mate the breadth of this flight at a mile, although I am quite positive
that it was more, and assumed that it travelled at the rate of a mile
a minute, I then obtain, in a duration of four hours, a length of 240
miles. If I further calculate three birds to every square yard, one
with another, I obtain for the entire flock a total of 2,230,272,000
Pigeons,—an apparently incredible number, though, in reality, pro-
bably far below the mark."
Doubtless food-supply is a great factor in the avial economy, and
birds not being a commercial people, if food does not come to them they
must go to it. This explanation might well serve for the insectivor-
ous Hirundinae, but exceptions are too numerous for it to be in any
way generally satisfactory. Even Edwards felt this : he says of the
Swift, "We cannot pretend to determine the cause why it leaves us
so early ; want of food cannot drive it from our climate, as insects
are then very plentiful in our island; neither can the severity of
the season compel it to quit this country, as the weather is usually
very warm when it departs" (l.c, p. 29). The sojourn of the
Swift and Cuckoo with us lasts only about thirteen weeks. The
Swift is the last summer migrant to arrive, generally at the end of
April, and the first to depart, generally early in August. All are
familiar with the vast power of flight possessed by the Swift ; it has
been aptly styled the true clipper of the air, but it is a bird most im-
patient of cold and many are the stories told of benumbed Swifts
being picked up, should any sudden decrease in the temperature
occur. Jesse says, "Just after the first appearance of Swifts this
year [April 18th, 1835], there was a remarkably cold day, preceded
by two as particularly warm. This cold day completely torpified the
Swifts, and they clustered together in lumps or masses, something
like a swarm of bees. A large cluster of these birds was seen
hanging to the water-spout of Harwich Church. Some boys were
able, with poles, to knock them down, and many were caught. A
Titmouse, with two exceptions only, from 1779 or 1785 to 1873. (" Ootheca Wolleyana," p. 98,
and Yarrell's Brit. Birds, 4th ed., i., pp. 58 note, 486).