"From every side they hurried in, Rubbing their sleepy eyes." Keats.
Of all the nearly eight hundred species of North American birds, the robin is without question the one most generally known. Its great commonness and wide distribution have something to do with this fact, but can hardly be said to account for it altogether. The [red-eyed vireo] has almost as extensive a range, and at least in New England is possibly more numerous; but except among ornithologists it remains a stranger, even to country-bred people. The robin owes its universal recognition partly to its size and perfectly distinctive dress, partly to its early arrival in the spring, but especially to the nature of its nesting and feeding habits, which bring it constantly under every one's eye.
It would seem impossible, at this late day, to say anything new about so familiar a bird; but the robin has one interesting and remarkable habit, to which there is no allusion in any of our systematic ornithological treatises, so far as I am aware, although many individual observers must have taken notice of it. I mean the habit of roosting at night in large flocks, while still on its breeding grounds, and long before the close of the breeding season. [14]
Toward the end of summer, two years ago, I saw what looked like a daily passage back and forth of small companies of robins. A friend, living in another town, had noticed similar occurrences, and more than once we discussed the subject; agreeing that such movements were probably not connected in any way with the grand southward migration, which, so far as we could judge, had not yet commenced, but that the birds must be flying to and from some nightly resort. The flocks were small, however, and neither of us suspected the full significance of what we had seen.
On the 19th of July, 1889, the same friend informed me that one of our Cambridge ornithologists had found a robin roost in that city,—a wood in which great numbers of birds congregated every night. This led me to keep a sharper eye upon my own robins, whom I had already noticed repeating their previous year's manœuvres. Every evening, shortly before and after sunset, they were to be seen flying, now singly, now by twos and threes, or even by the half dozen, evidently on their way to some rendezvous. I was suspicious of a rather distant hill-top covered with pine-trees; but before I could make it convenient to visit the place at the proper hour, I discovered, quite unexpectedly, that the roost was close by the very road up and down which I had been walking; an isolated piece of swampy wood, a few acres in extent, mostly a dense growth of gray birches and swamp white oaks, but with a sprinkling of maples and other deciduous trees. It is bounded on the further side by a wet meadow, and at the eastern end by a little ice-pond, with a dwelling-house and other buildings beside it, all within a stone's throw of the wood.
This discovery was made on the evening of July 25th, and I at once crossed a narrow field between the wood and the highway, and pushed in after the birds. It was too dark for me to see what was going on, but as I brushed against the close branches the robins set up a lively cackling, and presently commenced flying from tree to tree before me as I advanced, though plainly with no intention of deserting their quarters. The place was full of them, but I could form no estimate of their number.
On the following evening I took my stand upon a little knoll commanding the western end of the wood. According to my notes, the birds began to arrive about sunset,—but this was pretty certainly an error,—and though I did not undertake an exact count until the flight was mainly over, it seemed likely that at least three hundred passed in at that point. This would have made the total number twelve hundred, or thereabout, on the assumption that my outlook had covered a quarter of the circuit. After the flight ceased I went into the wood, and from the commotion overhead it was impossible not to believe that such a calculation must be well within the truth.
The next day was rainy, but on the evening of the 28th I stood by the shore of the pond, on the eastern side of the wood, and made as accurate a count as possible of the arrivals at that point. Unfortunately I was too late; the robins were already coming. But in fifty minutes, between 6.40 and 7.30, I counted 1072 birds. They appeared singly and in small flocks, and it was out of the question for me to make sure of them all; while I was busy with a flock on the right, there was no telling how many might be passing in on the left. If my observations comprehended a quarter of the circle, and if the influx was equally great on the other sides (an assumption afterward disproved), then it was safe to set the whole number of birds at five thousand or more. Of the 1072 actually seen, 797 came before the sunset gun was fired,—a proportion somewhat larger than it would have been had the sky been clear.
On the afternoon of the 29th I again counted the arrivals at the eastern end; but though I set out, as I thought, in good season, I found myself once more behind time. At 6.30 robins were already dropping in, notwithstanding the sky was cloudless. In the first five minutes eighteen birds appeared; at sunset 818 had been counted; and at 7.30, when I came away, the figures stood at 1267. "The robins came more rapidly than last night," I wrote in my notebook, "and for much of the time I could keep watch of the southeastern corner only. My vision then covered much less than a quarter of the circuit; so that if the birds came as freely from other directions, at least five thousand must have entered the wood between 6.30 and 7.30. As long as it was light they avoided passing directly by me, going generally to the left, and slipping into the roost behind some low outlying trees; though, fortunately, in doing this they were compelled to cross a narrow patch of the illuminated western sky. I suspect that the number increases from night to night. Between 6.40 and 7.30, 1235 birds came, as compared with 1072 last evening."