Head, nape, and back, bluish black; rump white: tarsi and toes feathered.
H. urbica, Temm. Man. d'Orn. torn. I. p. 428. Id. torn. III. p. 300. Martin, Mont. Orn. Diet. Selb. Must. vol. I. p. 123. pl. 42. f. 2. Bew. Brit. Birds, vol. I. p. 293.
Entire length five inches six lines: length of the bill (from the forehead) three lines, (from the gape) six lines; of the tarsus six lines; of the tail two inches six lines and a half; from the carpus to the end of the wing four inches four lines.
Head, nape, and all the upper region of the hack, glossy bluish black: wings and tail dusky brown; the latter forked, but not so long as in the last species: rump, and all the under parts from the chin to the vent, pure white: tarsi and toes covered with a white down. (Egg). Smooth, delicate white: long. diam. nine lines and a half; trans, diam. six lines.
Rather later in its arrival than the last species, being seldom observed in abundance before the end of April or beginning of May. Departs in October; but a few stragglers may occasionally be seen on to November. Food and habits similar to those of the Swallow: flight not so rapid. Nest usually fixed under the eaves of houses or in the angles of windows; formed entirely of mud externally, and lined with feathers. Lays four or five eggs, and has frequently two broods in the Summer. Congregates at the approach of Autumn.