The flight of this species is rapid, but unsteady and flickering. In searching for their food they skim low over the surface of both land and water, dropping upon the latter, as they fly, to drink or to bathe. Their food consists of the smaller kinds of winged insects, which they pursue and capture, dashing at them at times even on the water. They usually feed their young with larger kinds than they eat themselves.
It has not been observed in Greenland, but Richardson found it in colonies of thousands at the mouth of Mackenzie’s River, in the 68th parallel. It is a very social bird, usually breeding together in large communities, and is
more independent of man than most of its family, owing him no other favors than those incident to excavations through sand-banks, of which it avails itself. The nests of these Swallows are placed in excavations made by them in the banks of rivers, cliffs by the sea-shore, and similar favorable situations. These are usually as near the surface of the ground as the nature of the soil permits to be readily penetrated, though the bird has been known to work its way even through hard gravel. Their depth varies from fourteen inches to four feet, though two feet is the usual distance.
Mr. Augustus Fowler mentions a remarkable instance of sagacity and provident forethought in these birds, not easily separable from reason. In the town of Beverly, in a stratum of sandy loam, he observed each season a colony of some twenty or thirty pairs of these birds. In this place these birds never burrowed more than two or three feet. Within a mile of this place another colony excavated a bank in which the layer of loam was mixed with small stones. In this bank they excavated to the depth of five, seven, and even nine feet. Why was there this extraordinary difference in the length of burrows made by the same species, in situations not more than a mile apart? The reason for this difference, upon examination, became very obvious. We give the explanation in Mr. Fowler’s own words: “In one bank, where the earth was of a fine sandy loam, easily perforated, from the entrance to the extremity the burrows did not exceed three feet in length; while in the other bank, with harder loam to work in, one burrow was found nine feet in length. After examining six holes of nearly equal length, it appeared that these little birds had sufficient reason for extending their labors so far into the earth. In every instance, where they met with a spot free from stones they finished their burrows; thus showing great care for the welfare of their eggs or young by avoiding, in the stony soil, a catastrophe so great as would befall their treasures if by accident one of these stones should fall upon them.”
The work of perforation they perform with their closed bill, swaying the body round on the feet, beginning at the centre and working outwards. This long and often winding gallery gradually expands into a small spherical apartment, on the floor of which they form a rude nest of straw and feathers. The time occupied in making these excavations varies greatly with the nature of the soil, from four or five days to twice that number.
Their eggs are five in number, pure white, and when unblown have a fine roseate hue. They are oval in shape, larger at one end, and pointed at the smaller. Their average length is .72 of an inch, and their average breadth .47.
We now come to the consideration of three families of Oscine birds, of pre-eminently dentirostral type, having certain common characters by which they are distinguishable, with but little difficulty, from all others. In their close relationship it has been questioned by many whether they do not all belong under one head, but they are more generally considered distinct. The common characters, and those peculiar to each, are as follows:—
Common Characters. Bill stout, and considerably hooked at tip, or with the point bent abruptly downward; with a deep notch, and sometimes a tooth or lobe just behind the notch; the tip of the lower mandible likewise frequently bent up, and with a notch behind it. The nostrils lateral, the bristles of the mouth generally well developed. The primaries are ten (except in a few Vireos), the outer from one fourth to one half the second. Tail variable. Tarsi scutellate anteriorly; sometimes with a tendency to division on the lateral plates; hitherto not met with. Basal joints of toes more adherent. Separated from Turdidæ by greater adhesion of toes; from Troglodytidæ by notched and hooked bill, etc.