The ROCK SWALLOW (_Cotyle rupestris_) is about five inches and a half long, and from twelve and a half to thirteen and three-quarters broad; the wing measures about five inches. The coloration of the plumage closely resembles that of the rocks upon which this species principally lives. The upper parts of the body are light brown, the quills and tail blackish; the centre feathers that compose the latter are beautifully marked with oval yellowish white spots; the throat is whitish; the breast and belly dirty reddish grey; the eye is dark brown, the beak black, and the foot reddish grey. The sexes are nearly alike; the young are somewhat more uniform in hue than the adult bird. The actual habitat of the Rock Swallows appears to be Spain, Italy, and Greece, but they are constantly met with and are known to breed in the Tyrol, and even in still more central parts of Europe. So hardy are they that such as migrate do not leave till the autumn is far advanced, and return as early as February or March; whilst others, inhabiting the extreme south, remain in their native land throughout the entire year. In Egypt and South-western Asia they are replaced by a smaller but very similar species. The Rock Swallows seldom associate with their congeners, and are readily distinguished from them by their greyish hue, and comparatively slow and hovering flight. In Switzerland, after their return in the spring, they usually allow some time to elapse before they seek their own nests or build new ones; during the interval they busy themselves in making excursions in all directions, either skimming near the mountains, or, if the weather be fine, soaring to a considerable height in the air. If, on the contrary, the season be dull or rainy, they keep close to the earth, or beneath projecting rocks and stones. If the day be bright, they come down from their retreats among the mountains, and perch upon the roofs of cottages, but never venture actually into houses. The nest is placed beneath a projecting ledge of rock, or in some similar situation, and resembles that of the Chimney Swallow. Several pairs frequently build together, but we have never seen settlements like those formed by some other species. Many various statements have been made as to their mode of nidification, seeing that, owing to the precipitous nature of the localities selected, it is very often extremely difficult to approach the abode of a Rock Swallow. The eggs are white, spotted with red, and are from three to five in number. After the nestlings are fully fledged, they still remain for some time with the old birds, following them about in search of insects, which are caught on the wing, but as soon as a fly or a beetle is thus obtained, the hungry young perch for a moment upon a tree, and receive the morsel from the parent's beak. When the period of incubation is over, the different families form small parties, and wander about the country, as in the spring, until the