WARBLER, in ornithology, the name bestowed in 1773 by T. Pennant (Genera of Birds, p. 35) on the birds removed, in 1769, by J. A. Scopoli from the Linnaean genus Motacilla (cf. Wagtail) to one founded and called by him Sylvia—the last being a word employed by several of the older writers in an indefinite way—that is to say, on all the species of Motacilla which were not wagtails. “Warbler” has long been used by English technical writers as the equivalent of Sylvia, and is now applied to all members of the sub-family Sylviiae of the thrushes (q.v.), and in the combination “American warblers” to the distinct passerine family Mniotiltidae. The true warblers (Sylviinae) are generally smaller than the true thrushes Turdinae (see Thrushes), with, for the most part, a weak and slender bill. They seldom fly far, except when migrating, but frequent undergrowth and herbage, living on insects, larvae and fruit. The song is unusually clear and very sweet, with frequently a metallic sound, as in the grasshopper warbler. The nest is usually cup-shaped and well lined, and from three to six eggs (twelve in Regulus), usually spotted, are laid.

The true warblers are chiefly Old World, visiting the southern Old World in winter, but members of the sub-family occur in New Zealand, Polynesia and Panama. Amongst the commonest in England is the well-known sedge-bird or sedge-warbler, Acrocephalus schoenobaenus, whose chattering song resounds in summer-time from almost every wet ditch in most parts of Britain. As is the case with so many of its allies, the skulking habits of the bird cause it to be far more often heard than seen; but, with a little patience, it may be generally observed flitting about the uppermost twigs of the bushes it frequents, and its mottled back and the yellowish-white streak over its eye serve to distinguish it from its ally the reed-wren or reed-warbler, A. streperus, which is clad in a wholly mouse-coloured suit. But this last can also be recognized by its different song, and comparatively seldom does it stray from the reed-beds which are its favourite haunts. In them generally it builds one of the most beautiful of nests, made of the seed-branches of the reed and long grass, wound horizontally round and round so as to include in its substance the living stems of three or four reeds, between which it is suspended at a convenient height above the water, and the structure is so deep that the eggs do not roll out when its props are shaken by the wind. Of very similar habits is the reed-thrush or great reed-warbler, A. arundinaceus, a loud-voiced species, abundant on the Continent but very rarely straying to England. Much interest also attaches to the species known as Savi's warbler, Locustella luscinioides, which was only recognized as a constant inhabitant of the Fen district of England a few years before its haunts were destroyed by drainage. The last example known to have been obtained in this country was killed in 1856. The nest of the species is peculiar, placed on the ground and formed of the blades of a species of Glyceria so skillfully entwined as to be a very permanent structure, and it is a curious fact that its nests were well known to the sedge-cutters of the district which it most frequented, as those of a bird with which they were unacquainted, long before the builder was recognized by naturalists. In coloration the bird somewhat resembles a nightingale (whence its specific name), and its song differs from that of any of those before mentioned, being a long smooth trill, pitched higher but possessing more tone than that of the grasshopper-warbler Locustella naevius—which is a widely distributed species throughout the British Isles, not only limited to marshy sites, but affecting also dry soils, inhabiting indifferently many kinds of places where there is tangled and thick herbage, heather or brushwood. In those parts of England where its was formerly most abundant it was known as the reeler or reel-bird, from its song resembling the whirring noise of the reel at one time used by the spinners of wool. The precise determination of this bird—the grasshopper lark, as it was long called in books, though its notes if once heard can never be mistaken for those of a grasshopper or cricket, and it has no affinity to the larks—as an English species is due to the discernment of Gilbert White in 1768. In its habits it is one of the most retiring of birds, keeping in the closest shelter, so that it may be within a very short distance of an eager naturalist without his being able to see it—the olive colour, streaked with dark brown, of its upper plumage helping to make it invisible. The nest is very artfully concealed in the thickest herbage. The foreign forms of aquatic warblers are far to numerous to be here mentioned.

The members of the typical genus Sylvia, which includes some of the sweetest singers, are treated under Whitethroat; and the willow- or wood-wrens under Wren. The Australian genus not inaptly so named, since in beauty they surpass any others of their presumed allies, is now placed in with the Old World flycatchers in the family Musicapidae. Part of the plumage of the cocks in breeding-dress is generally some shade of intense blue, and is so glossy as to resemble enamel, while black, white, chestnut or scarlet, as well as green and lilac, are also present in one species or another, so as to heighten the effect. But, as already stated, there are systematists who would raise this genus, which contains some 15 species, to the ranks of a distinct family, though on what grounds it is hard to say.

The birds known as “American warblers,” forming what is now recognized as a distinct family, Mniotiltidae, remain for consideration. They possess but nine instead of ten primaries, and are peculiar to the New World. More than 130 species have been described, and these have been grouped in 20 genera or more, of which members of all but three are at least summer-visitants to North America. As a whole they are much more brightly coloured than the Sylviinae, for, though the particular genus Mniotilta (from which the family takes its name) is one of the most abnormal—its colours being plain black and white, and its habits rather resembling those of a Tree-creeper (q.v.)—in other groups chestnut, bluish-grey and green appear, the last varying from an olive to a saffron tint, and in some groups the yellow predominates to an extent that has gained for its wearers, belonging to the genus Dendroeca, the name of “golden” warblers. In the genus Setophaga, the members of which deserve to be called “fly-catching” warblers, the plumage of the males at least presents yellow, orange, scarlet or crimson.

The Mniotiltidae contain forms exhibiting quite as many diverse modes of life as do the Sylviinae. Some are exclusively aquatic in their predilections, others affect dry soils, brushwood, forests and so on. Almost all genera are essentially migratory, but a large proportion of the species of Dendroeca, Setophaga, and especially Basileuterus, seem never to leave their Neotropical home; while the genera Leucopeza, Teretristis and Microligia, comprising in all but 5 species, are peculiar to the Antilles. The rest are for the most part natives of North America, where a few attain a very high latitude,[1] penetrating in summer even beyond the Arctic Circle, and thence migrate southward at the end of summer or in the fall of the year, some reaching Peru and Brazil, but a few, as, for instance, Parula pitiayumi and Geothlypis velata, seem to resident in the country last named.  (A. N.) 

  1. Seven species have been recorded as wandering to Greenland, and one, Dendroeca virens, is said to have occurred in Europe (Naumannia, 1858, p. 425).