The MARTIN or ROOF SWALLOW (Chelidon urbica) we have selected as the type of a group, recognisable by their slightly forked tail and strong feet, the toes of which are connected from the first joint, and, like the tarsi, are thickly covered with feathers. This bird is five inches and a half long, and ten and three-quarters broad; the wing measures four inches, and the tail two and a half. Upon the back the plumage is almost entirely of an uniform blueish black; the under side and rump are white. The eye is dark brown, the beak black, and the bare parts of the foot black. Both sexes are alike in colour, but the plumage of the young is less clear in its tints than that of the adult. The Martin inhabits the whole of Europe, and penetrates further north than the Chimney Swallow; it is numerous in Siberia, and during its migrations visits the interior of Africa and Southern Asia. In most respects it closely resembles the species already described, but is somewhat less brisk and intelligent; its flight also is not so rapid and varied as that of the Chimney Swallow, but it frequently soars to an enormous height in pursuit of the insects upon which it subsists. Its voice is very far inferior to that of the rest of its family, and its cry monotonous and harsh.
In populous districts the nests of this bird are invariably constructed upon houses, but where human habitations are scarce, the Roof Swallow is content to make its preparations upon rocks, or any situation that will afford it a secure shelter from the wind and rain. The nest is very similar to that of the Chimney Swallow, but with this difference, that it is always built against a hole, and has no external entrance; sometimes many pairs construct their dwellings under the same eaves or the same rock, and thus form a kind of settlement. Although usually peaceful, during the breeding season disputes and battles are of constant occurrence; each couple naturally endeavouring to obtain the snuggest corner, and to oust its neighbour should the opportunity offer. The brood consists of from four to six delicate snow-white eggs, and the nestlings are hatched in about twelve days. The female alone broods, and is fed by her mate only when the weather is fine; the young also frequently have but an insufficient supply of food, owing to the difficulty of procuring insects when the season is inclement, and thus must very often be left behind when the flocks migrate, as they are still too weak to undergo such great fatigue. If all goes well, the nestlings are fully fledged in about sixteen days, but generally remain for some time longer under the care of their parents. During this period the whole family return at night to their nest, which they fill so completely that we have often been inclined to wonder that the walls did not give way under the pressure to which they were subjected. Desperate fights often ensue when a stray bird finds its way into a wrong nest, and most courageously do those in possession exert themselves to expel the intruder, who is generally equally determined to remain. Far less brave is the Swallow when brought into collision with its principal enemy, the Sparrow; it often happens that no sooner is the Swallow's nest completed than a male Sparrow creeps in and takes possession, keeping guard at the door, in order to prevent the entrance of the rightful owner; under these circumstances, the latter, not venturing to obtain admittance by force, usually summons its companions, who together beset the impudent intruder with loud cries and every demonstration of anger. In most cases the Sparrow retains possession of its ill-gotten abode, but should the Swallow be bold, a battle sometimes takes place that proves fatal to one or other of the combatants. So constant are these attempts of the Sparrow to obtain a home for its young, that a pair of Swallows sometimes are deprived twice in the season of the domicile they have laboriously completed, and, should this occur, do not breed at all that year. It was formerly imagined that the Swallow revenged itself on its foe by building it up in the nest, but we need hardly say that this is untrue.
The Martins make their appearance in England a few days after the Chimney Swallow (Cecropis-Hirundo-rustica), and on their arrival are usually seen in warm and low situations, such being most likely to supply an abundance of their natural food. They are equally distributed throughout the kingdom, and are found wherever man has fixed his residence, seeming to court his protection. They commence nidification early in May, and build in the upper angles of windows and under the eaves of houses, sometimes under the arches of bridges or against the face of rocks. The nest is formed of mud completely worked and cemented, and is closed all round except a small orifice, usually on the sheltered side, just of sufficient size to permit the passage of the inhabitant; the interior is well lined with a collection of straw, hay, and feathers. These birds leave us in October; preparatory to their departure, they congregate in great numbers on the roofs of houses.
The MOUNTAIN or SHORE SWALLOWS (Cotyle) are recognisable by their slightly forked tail, and lax, lustreless plumage. Two species are indigenous to Europe; a description of these will serve for the entire group.
THE ROCK SWALLOW.
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 proper time for commencing their migrations. In its general disposition, the Rock Swallow is less alert and brisk than its congeners, and its voice has a deeper and rather hoarse sound.
THE SAND MARTIN.
The SAND MARTIN (Cotyle riparia), one of the smallest members of its family, is only five inches long and eleven broad; the wing measures four, and the tail two inches. The plumage is greyish brown above, white beneath, and marked on the breast with a greyish brown ring. The sexes are nearly alike, but the young are darker than the adults. These birds inhabit and breed in all parts of Europe, except the extreme northern countries, and usually frequent such rocks or hills as overhang streams and rivers. The wonderful nests that have rendered the members of this group so famous, are made either in natural hollows, or in holes excavated with enormous labour by the builders; they appear, however, to prefer the cavities which they have themselves prepared, and are most careful to dig their retreats at such an elevation as to be above high-water mark. "It appears," says Naumann, "almost incredible that a pair of these small birds, with no other instruments than their delicate beaks, can dig, as they do, a horizontal passage several inches in diameter, and from three to six feet deep, in the space of two, or sometimes three days. The male and female both assist in this, for them, gigantic undertaking, and work with the utmost energy and ardour, disposing of the loose earth by throwing it out behind them with their feet; and yet, strange to say, it is not uncommon for them suddenly to leave one of these excavations when almost finished, and commence another; occasionally, they will even dig a third. Why they do this has never been satisfactorily ascertained, for it is only the passage to the chamber in which the nest is made that is ever occupied either by the parents or the young family. Many pairs invariably work close together, thus forming an extensive settlement, and it is most amusing to watch the earth flying out of a number of their holes as it is ejected by the busy labourers, who are usually quite out of sight." It is to these settlements that Pliny alludes in the following amusing terms: "At the Heracleotic mouth of the Nile in Egypt, the Swallows present an insuperable obstacle to the inroads of that river, by the embankment formed by their nests in one continuous line, nearly a stadium in length—a thing that could not possibly have been effected by the agency of man. In Egypt, too, near the city of Coptos, there is an island sacred to Isis; in the early days of spring, the Swallows strengthen the angular corner of this island with chaff and straw, thus fortifying it in order that the river may not sweep it away. This work they persevere in for three days and nights together, with such unremitting labour that it is a well-known fact that many of them die in consequence of their exertions; moreover, this is a toil which recurs to them regularly every year."