The swallow has a variety of sharp little chirps and twittering notes, and a loud, startled, double alarm-note, uttered at the appearance of a hawk speeding through the air, or at sight of a prowling cat. The appearance of a hawk excites as much anger as fear, and he generally goes in pursuit of it; but the note is understood by other small birds, and has the effect of sending them quickly into hiding. The song, uttered sometimes on the wing, but more frequently when perched, is very charming, and seems more free and spontaneous than that of any bird possessing a set song, the notes leaping out with a heartfelt joyousness which is quite irresistible. The sound differs in quality from that of other birds; it is, perhaps, more _human_: a swallow-like note may be heard in some of the most beautiful contralto voices. The dozen or more notes composing the song end with a little jarring trill, so low as to be hardly audible. A favourite site for the swallow’s nest is the top of a joist supporting the rafters of a barn or other outhouse to which there is free access. It is a saucer-shaped rim of mud or clay, placed on the wood. The inside is lined with dry grass and feathers. It is quite open at the top, but usually close to the roof. The eggs are four to six in number, and vary much in shape and disposition of markings. They are pure white, spotted with rich coffee-brown, light reddish brown, and purplish grey. During incubation the sitting-bird is fed at intervals by her mate. Two broods are reared in the season, and the young are fed for some days after quitting the nest. The early broods are believed to leave this country in advance of the adults and the young of the later broods. The final and principal migration takes place at the end of September or early in October, the birds congregating some days before departure in large flocks, sometimes numbering many thousands. Martin. Chelidon urbica. [Illustration: FIG. 45.--MARTIN. ⅓ natural size.] Head, nape, and upper part of the back black, with violet reflections; lower parts of the back and under parts pure white. Feet and toes covered with downy feathers; tail forked. Length, five and a half inches. * * * * *