THE CHIMNEY SWIFT 57 
it will be noticed that he spreads his tail for an 
instant whenever he changes suddenly the direc- 
tion of his flight. In other words, he uses his 
tail as a rudder. 
He shoots about the sky at a tremendous 
speed, much of the time sailing, with his long, nar- 
row wings firmly set, and is especially lively and 
noisy toward nightfall. Very commonly two or 
three of the birds fly side by side, cackling 
merrily and acting very much as if they were 
amusing themselves with some kind of game. 
They feed on the wing, and have wide, gaping 
mouths perfectly adapted to that purpose. 
As their name implies, they build their nests 
and pass the night mostly in chimneys, although 
in the wilder parts of the country they still 
inhabit hollow trees. Numbers of pairs live 
together in a colony. 
One of the chimneys of a certain house near 
the Charles River, in Newton, Massachusetts, has 
for many years been a favorite resort of swifts. 
I have many times visited the place to watch the 
birds go to roost. Little by little they gather in 
a flock, as twilight comes on, and then for an 
hour or more the whole company, hundreds in 
number, go sweeping over the valley in broad 
circles, having the chimney for a centre. Grad- 
ually the circles become narrower, and at the 
