Oporornis agilis.
Habits. Of the history of this rare and beautiful species but little is as yet known. It was first met with by Wilson, in the State of Connecticut, and he afterwards obtained two other specimens near Philadelphia. Others have since been procured at Carlisle, Penn., at Washington, Loudon County, Va., near Chicago, Racine, and in Southern Illinois. September 25 to October 1, and May, from the 15th to the 28th, appears to be the epoch of their fall and spring occurrence. They are more frequently noticed in the autumn. It is supposed to be a migratory bird, going north to breed.
It was found by Wilson, in every case, among low thickets, and seemed to be more than commonly active, not remaining for a moment in the same position. Mr. Audubon obtained only two specimens, a pair, opposite Philadelphia in New Jersey. When he first observed them they were hopping and skipping from one low bush to another, and among the tall reeds of the marsh, emitting an oft-repeated tweet at every move. They were chasing a species of spider that ran nimbly over the water, and which they caught by gliding over it. Upon dissecting them, he found a number of these spiders in their stomachs, and no other food. These two birds were not at all shy, and seemed to take very little notice of him, even when close to them.
Mr. Trumbull, in his list of the birds of Eastern Pennsylvania, marks it as a summer resident of that State, which is probably not the fact. Mr. Lawrence includes it in his list of birds found near New York City. It is not given by Mr. Verrill or Mr. Boardman as occurring in any part of Maine, and has not been detected in Western Massachusetts by Mr. Allen, though it has been occasionally met with in the eastern part of the State by Dr. Cabot, Mr. Maynard, and others. More recently, in the fall of 1870, and again in that of 1871, this species has been found quite abundant in a restricted locality in the eastern part of that State. It was first observed by Mr. H. W. Henshaw, a promising young naturalist, in the early part of September, 1870, among the Fresh Pond marshes in Cambridge. They appeared to be quite
numerous, and several specimens were obtained. He communicated the discovery to his friend, Mr. William Brewster, and more than fifty specimens of this rare Warbler were obtained during that season. In the following autumn, in September and during the first few days of October, these birds were observed in the same locality, apparently in greater numbers, and more specimens were obtained.
Mr. Henshaw writes me that he first saw this species, September 7, 1870, when he obtained a single specimen. From that time until September 27 it was very common throughout the Fresh Pond swamps, to which locality it seemed to be restricted. It again made its appearance in 1871, and at about the same time, and remained until October 5. It was in even greater numbers than during the preceding year.
Their habits, while with us in the fall, appear to be very different from those of the individuals observed by Wilson and Audubon, which were described as being of a remarkably lively disposition, and hence the name of agilis. Mr. Henshaw found them almost constantly engaged in seeking their food upon the ground. When startled, they would fly up to the nearest bush, upon which they would sit perfectly motionless, in a manner closely resembling the Thrushes. If not further disturbed, they immediately returned to the ground and resumed the search for food among the leaves. If greatly startled, they took a long flight among the bushes, and could rarely be found again. The only note he heard them utter was a single sharp chirp, emitted occasionally, when surprised. They were all remarkably fat, so much so as to make it difficult to obtain a good specimen.
About sunset, standing on the skirts of the swamp, he has repeatedly observed these birds alight, in great numbers, on the edge, and immediately pass in, evidently intending to remain there over night. He judged that they migrate entirely by day. On only one or two occasions did he observe these birds feeding in the tops of willow-trees. At such times they appeared equally lively in their movements with the Dendroica striata, in company with which they were associated. The birds he saw were nearly all in immature plumage, adults being comparatively rare.
Dr. Coues states that the Connecticut Warbler is found near Washington in the month of October, but that it is rather uncommon. He did not meet with it in spring. He speaks of its frequenting old buckwheat and corn fields, searching for food among the dry, rank weeds, and also in swampy places among low thickets.