As soon as the welcome note of the Purple Martin is heard in spring, on its return to the United States, which, in Louisiana, sometimes takes place early in March, the little Warbler here presented to your inspection follows, and is seen gaily moving from tree to tree, feeding on the smaller insects, and tuning its pipe, which, however, is not the most melodious. It approaches the gardens and orange-groves, and again flies off to the willows, along the margins of the pools and lagoons. Its sojourn is of short duration in Louisiana, for it moves gradually eastward as the season advances. Its migration, in as far as I have been able to ascertain, is principally performed during the night. I have observed many in the course of one day in a place, which, next day, if the weather had become warm, scarcely contained a single individual. I have seen many of these birds, as well as their nests, on the Genessee river; but in the States of New York, Connecticut, Pennsylvania, Maryland, and Virginia, they may be found in every orchard and garden, and even in the streets, among the foliage of our trees.

The males chase each other with great courage, and fight for a few moments, to establish their claim to any particular spot or tree, after which they are seen climbing up and down among the twigs and smaller branches, looking keenly among the leaves and blossoms for insects. Careless of the presence of man, the Blue-eyed Warbler is easily approached. The same carelessness makes it build its little nest almost always within reach. The parents are very assiduous in the discharge of their duties. They construct a nest about the middle of May, in the forked branches of a small tree, often within a few paces of a house. The nest is strongly fastened to the twigs, is formed externally of hemp, flax, or woolly substances, and is well lined with different kinds of hair, intermixed with softer materials. It breeds twice during the summer, and returns southward in the beginning of autumn, in small parties, shifting chiefly by night. During the breeding-season, this little bird, when approached, shews great anxiety for the preservation of its eggs or young, and tries, with all the artifices employed by many other species, to entice the aggressor away from its nest. They are seen, on their return to the south, passing through Louisiana in October.

Its migrations northward are almost as wonderful as those of several other birds, that seem, as it were, not to have been endowed with sufficient power of flight to enable them to traverse a vast extent of country. Yet it proceeds in summer as far as the 68th parallel, where it was found by Dr. RICHARDSON in numbers and breeding. Although it comes into the United States from the south at the early period mentioned, thousands follow in the wake of the first that are seen in Louisiana, for, I met with great numbers during the whole month of April, when on my way to the Texas, as well as after my arrival in that country, where they threw themselves into all the bushes along the sea-shore, apparently for the purpose of spending the night. At this period they are quite silent, and many of them have not yet obtained the reddish spots on the breast so conspicuous at a later season.

Mr. NUTTALL was the first naturalist who observed the very curious method in which it contrives to rid itself of the charge of rearing the young of the Cowbird. "It is amusing," he says, "to observe the sagacity of this little bird in disposing of the eggs of the vagrant and parasitic Cow Troopial. The egg deposited before the laying of the rightful tenant, too large for ejectment, is ingeniously incarcerated in the bottom of the nest, and a new lining placed above it, so that it is never hatched to prove the dragon of the brood. Two instances of this kind occurred to the observation of my, friend Mr. CHARLES PICKERING; and last summer I obtained a nest with the adventitious egg about two-thirds buried, the upper edge only being visible, so that, in many instances, it is probable that this species escapes from the unpleasant position of becoming a nurse to the sable orphan of the Cowbird. She, however, acts faithfully the part of a foster-parent when the egg is laid after her own."

The following note from my friend Dr. T. M. BREWER shews that this little bird is capable of still greater exploits, "There is a very interesting item in the history of the Yellow-poll Warbler, which has been noticed only within a few years, and which is well deserving of attention, both for the reasoning powers which it exhibits, and for its uniqueness, for it is not known, I believe, to be practised by any other bird. I allude to the surprising ingenuity with which they often contrive to escape the burden of rearing the offspring of the Cow Troopial, by burying the egg of the intruder. I have known four instances in which single eggs have been thus buried by the Yellowbird's building a second story to her nest, and enclosing the intruder between them. In one instance, three of the Sylvia's own eggs were thus covered along with that of the Cow Blackbird, and in another, after a Blackbird's egg had been thus concealed, a second was laid, which was similarly treated, thus giving rise to a three-storied nest. This last you have in your possession, and will, I hope, give to the world a drawing as well as a complete description of it. The Summer Yellowbird raises only one brood in the season in Massachusetts. The eggs, four or five in number, measure 5 1/2 eighths in length, by a trifle more than half an inch in breadth; they are of a light, dull bluish-white, thickly sprinkled with dots and small markings of various sizes of dull reddish-brown, accumulated towards the great end.

The fabric alluded to above may be thus described. A nest of the usual form had been constructed, of which the external diameter was three inches. It is composed of cotton rudely interwoven with flaxen fibres of plants, and lined with cotton of a reddish colour, with some hairs round the inner edges. The egg of the Cowbird having been deposited in this nest, another of a larger size, three inches and three-quarters in external diameter, has been built upon it, being formed of the same materials, but with less of the flaxen fibres. The egg is thus surmounted by a layer three-quarters of an inch thick, and was discovered by opening the lower nest from beneath. It is agglutinated to the lining of the nest, having been addled and probably burst. In this second nest a Cowbird had also deposited an egg, which was, in like manner, covered over by a third nest, composed of the same materials, and of nearly the same size as the second.

The birds represented in the thirty-fifth plate of my large work, and dedicated to Mr. CHILDREN, I have since found to be the young of this bird, probably of a late brood of the previous year, they having been found breeding at a period when this species shews few or none of the reddish spots on the breast, the want of which induced me to consider them as of a distinct species. These circumstances I mentioned to the Prince of MUSIGNANO, in London, my friend Dr. BACHMAN and myself having discovered the error soon after the publication of my first volume of Ornithological Biography.

I made my drawing of this species near Natchez, and having killed the specimen while it was searching for insects among the flowers of a large climbing plant, I have figured part of the latter also. This plant I have never seen, excepting in low, damp or marshy places. It there runs over decayed trees, spreading in the form of a bower, and hanging in graceful festoons. The long pendulous clusters of pale purple flowers are destitute of odour.

All our little birds known by the name of Warblers, and referred by authors to the genera Sylvicola, Trichas, and Vermivora, present the same structure in their digestive and respiratory organs. Their oesophagus is rather narrow, without dilatation; the proventriculus bulbiform, with numerous oblong glandules; the stomach rather small, oblique, elliptical or roundish, with the lateral muscles distinct, but of moderate thickness, the lower muscle thin, the epithelium dense, reddish-brown, and longitudinally rugous when not filled; the intestine rather short and of moderate width; two very small coeca; the rectum gradually enlarged. The trachea is composed of from 60 to 80 rings, flattened, somewhat tapering; the bronchi of ordinary size, of from 12 to 15 rings; there are cleido-tracheal muscles, lateral muscles, sterno-tracheal, and four pairs of inferior laryngeal.

BLUE-EYED WARBLER, Sylvia citrinella, Wils. Amer. Orn., vol. ii. p. 111.
SYLVIA OESTIVA, Bonap. Syn., p. 83.
YELLOW-POLL WARBLER, Sylvia oestiva, Aud. Orn. Biog., vol. i. p. 476; vol. v. p. 453. Adult Male.
CHILDREN'S WARBLER, Sylvia Childrenii, Aud. Orn. Biog., vol. i. p. 180. Young.

Outer four quills nearly equal, second longest; tail emarginate. Male with the upper parts pale yellowish-green, the rump greenish-yellow, the fore part of the head, cheeks, throat, sides of the neck and lower paints pure yellow, the breast and sides streaked with brownish-red; feathers of the wings deep brown, primaries margined with yellowish-green, secondaries, their coverts, and the first row of small coverts with yellow; tail-feathers brown, with the greater part of the inner webs and a portion of the outer, yellow, excepting the middle two. Female similar, but with the colours less bright, and the streaks on the breast and sides obsolete. Young with the upper parts yellowish-green, tinged with brown; forehead, sides of head, and lower parts deep yellow.

Male, 4 3/4, 8.

From Texas northward, and throughout the interior. Abundant. Migratory.