On the twenty-third of June another call was made on the night-hawk family, when I found two odd-looking bairns in the nest, if nest it could be called. They were covered with soft down, the black and white of which presented a wavy appearance. Their short, thick bills were covered with a speckled fuzz, except the tips. I stooped down and smoothed their downy backs with my hand, but there was no expression of fear in their sluggish eyes.
Both parents were present on the twenty-sixth of June. For a while the male bird pursued his mate savagely through the air, as if venting on her his anger at my intrusion, and then, mounting far up toward the sky and poising a moment, he plunged toward the earth with a velocity that made my head dizzy, checking himself, as is his wont, with a loud resounding Bo-o-m-m. The female again pursued her unwelcome visitor, swooping so near my head two or three times that I could have reached her with my cane. The cock bird, curiously enough, never displayed so much courage, but kept at a safe distance.
On the twenty-ninth the young birds had been moved about a half rod from the original site of the nest, and hopped off awkwardly into the grass when I tried to clasp them with my hand. The benedict was absent this time, and was never seen on any of my subsequent visits while the young birds were fledging. By the first of July the bantlings hopped about in a lively manner at my approach to their domicile, and wheezed in a frightened way, spreading out their mottled pinions. On the seventh of July neither of the parents was to be seen, and the youngsters sat so cosily side by side on the ground that I had not the heart to disturb their slumbers. Approaching cautiously on the tenth, I almost stepped on the mother bird before she flew up. At the same moment both young birds started from the ground, and fluttered away in different directions on their untried wings, their flight being awkward and labored. A few weeks later four night-hawks were circling about above the marsh,—no doubt the family that had been affording me such an interesting study. What was my surprise when one of them resented my presence by swooping down toward me, as the female had done a few weeks before!
Reference has already been made incidentally to the night-hawk’s curious habit of “booming,” as it is called. This sound is always produced as he plunges in an almost perpendicular course from a dizzy height,—or, more correctly, at the end of that headlong plunge, just as he sweeps around in a graceful curve. There is something almost sepulchral about the reverberating sound. How it is produced is a problem over which there has been no small amount of discussion in ornithological circles. But after considerable study of this queer performance, I am persuaded that it is a vocal outburst, produced either for its musical effect (though it is far from musical), or else to give vent to the bird’s exuberance of feeling as he makes his swift descent.
His thick, curved bill seems admirably adapted to produce this sound, as do also his arched throat and neck. It has seemed to me, too, that his mandibles fly open at the moment the boom is heard, although I cannot be sure such is the case. Besides, the peculiar chuckle, previously referred to, had about it a quality of sound suggestive of kinship with the bird’s resounding boom. The hollow, wheezy alarm-call of the young birds, heard on several of my visits to the nest in the marsh, corroborates this theory. But there is still further proof that this hypothesis is correct. The night-hawk often makes his headlong plunge without booming at all, but merely utters his ordinary rasping, aerial call, which has been translated by the syllable Spe-ah. Then he sometimes combines the two calls, and on such occasions both of the sounds are uttered with a diminished loudness, as one would expect if both are vocal performances, but as one would not expect if the booming were made by the concussion of the bird’s wings with the resisting air, as some ornithologists suppose. The female sometimes booms, but her voice obviously lacks the strong, resounding quality that characterizes the voice of her liege lord.
XIII.
A BIRDS’ GALA-DAY.
In Mr. Emerson’s poem entitled “May Morning” this stanza occurs:—
“When the purple flame shoots up,
And Love ascends the throne,
I cannot hear your songs, O birds,