This Swallow, in the more thickly settled portions of the country in which it breeds, exhibits a marked departure in many of its habits from those observed in wilder regions. In the latter places we find it a comparatively wild species, avoiding the society of man, and breeding exclusively in hollow trees and stumps, and deserving the name by which it is known in the British Provinces, of the “Wood Swallow.” In the islands of Grand Menan, in 1851, where repeated attempts had been made to induce these birds to build in martin-boxes, the endeavor had been entirely unsuccessful. Yet the birds were so abundant that hardly a hollow tree or stump, on certain of the smaller islands, could be found, that did not contain a nest of this species. This is still the case on the Pacific coast, though not exclusively so. It was not until after the publication of his Ornithological Biography that Audubon was aware of any departure from this mode of nesting on the part of this Swallow, although it had not escaped the notice of Wilson.
In Eastern Massachusetts these birds have undergone an entire change of
habit, breeding there exclusively in martin-boxes, and rarely, if ever, nesting in hollow trees,—a fact perhaps attributable to the scarcity of these opportunities along the sea-coast, where this bird is principally found. In Western Massachusetts, Mr. Allen states them to be not very common and the least abundant of the Swallows. Any sheltered and accessible box, however rough it may be, will answer its purpose, whether the more elaborate martin-house, or a mere candle-box with an open end. Mr. Audubon has known them to drive away a Barn Swallow from its nest, and to take possession, but this was probably exceptional. In one case, two small houses for birds put up in the same yard were taken possession of by a single pair of Swallows, and nests built in each; only one, however, of these was made use of. Whether this freak was the result of indecision or from a grasping selfishness, it is not possible to conclude, but apparently the former.
In the rural districts, even on the coast, these birds are not so abundant as in the cities, as in the latter they are less annoyed by other birds. The common Robin is often especially aggressive, seeking to drive them off his assumed premises. In one instance the Robin has been known to station himself on a platform in front of its nest for hours, and persistently refuse to permit its visits. Assistance was sought, and all the Swallows in the neighborhood came to the rescue. They sailed with angry cries over the head of the offender, at times darting down upon him as if to strike at him, but accomplishing nothing. The besieger maintained his ground until the writer intervened and drove him away, when the Swallows once more took possession, and fed their hungry nestlings in peace.
This species breeds from about latitude 38° to the extreme northern regions, and along the Arctic seas, wherever facilities for nesting are found. Richardson found them breeding in hollow trees on the Mackenzie River, in latitude 65°. Everywhere on both coasts they are very common, but are less numerous in the interior. Mr. Dall found it in Alaska from Fort Yukon to the sea. It was known to the Russians as the River Swallow. It was also met with in Sitka, by Bischoff. It has not been observed in Greenland.
During the breeding-season this species is more quarrelsome than any of its kindred, and is often more than a match for larger birds. Coming earlier in the season than the Purple Martin, it will often intrude itself into its premises and maintain possession. They are devotedly attached to their offspring, and bewail any accidents to them or any threatened peril. The same pair will return year after year to the same premises, and they soon become on familiar terms with the members of a family they frequently meet, so much so as to watch, when they have received materials for their nests, for a further supply, and will fly close to the person from whom they receive them. A pair which had thus, year after year, received supplies of feathers for their nests from the younger members of the family in whose yard their nest was built, would almost take them from the hands of their providers. This pair sat so close as to permit themselves to be taken from their nest, and when
released would at once fly back to their brood. They build a loose, soft, and warm nest of fine soft leaves and hay, abundantly lined with down and feathers, with which the eggs are not unfrequently covered. The addition of soft and warm materials is often made during incubation, and the nest is thoroughly repaired before it is used for a second brood, of which they usually have two in a season.
The eggs are of a uniform pure white, and are never spotted. They have a delicate pinkish shade before they are blown. They are of an oblong-oval shape, one end more pointed than the other, and they vary considerably in size. They vary in length from .75 to .875 of an inch, and in breadth from .50 to .56.
Mr. Hepburn states that the great mass of these birds leave California in August, but that a few are resident during the winter. The principal accession to their numbers takes place about the end of February, and they become quite abundant by the end of March. In Vancouver they are a month later. In 1853 Mr. Hepburn states that a pair constructed their nest in a piece of canvass at the end of the yard-arm of a store-ship that lay off the levee at Sacramento. He first noticed them on the 28th of April, when the nest had already made some progress. By the 19th of May there were seven eggs in it which were slightly incubated. The nest was a great mass of hay and dried grasses, in the midst of which was a cup-shaped depression very neatly lined with feathers, some of which bent over, forming a slight dome.
Hirundo thalassina, Swains.