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(Phylloscopus sibilatrix.) ALTHOUGH often taken to comprehend h every species of warbler, Professor Newton has recently shown that the genus Sylvia of Latham should be restricted to the group of fruit-eating warblers next to be described, and that the generic term which has priority for the willow wren group is Phylloscopus of Boie.
From its larger size, brighter colour, and finer song, the Wood Warbler deserves to be first
1 Yarrell, “ Hist. Brit. Birds,” 4th ed. vol. i. pp. 427, 442.
noticed; and the first step should be to distinguish it from its congeners. Perhaps none of the small insectivorous birds have been more confounded one with another than have the members of this group, not only by observers of the living birds, but by naturalists with skins of each before them. Taking the three species which annually visit us—i.e., the Wood Warbler, the Willow Warbler, and the Chiff-chaffit will be found on comparison that they differ in size as follows
Length. Wing. Tarsus. Wood Warbler · 5'2 in. . 3.o in. . 0:7 in. Willow Warbler , 5'0 , 26 , . 0°7 , Chiff-chaff . . . 4o7 „ . 24 „ . 0:6 ,
Not only is the Wood Warbler the largest of the three, but it has comparatively the longest wings and the longest legs. The wings, when closed, cover three-fourths of the tail. In the Willow Wren, under the same circumstances, less than half the tail is hidden. The Chiffchaff's wing is shorter again. In my edition of White's “Selborne,” founded upon that of Bennett, 1875, pp. 56, 57, will be found a long footnote on the subject, with woodcuts illustrating the comparative form of the wing in these three birds. Mr. Blake-Knox, in “ The Zoologist” for 1866, p. 300, has pointed to the second quill-feather, depicted in a sketch accompanying his communication, as being an unfailing mark of distinction. When we reflect, however, upon the variation which is found to exist in the length of feathers, owing to the age of the bird, moult, or accident, too much stress ought not to be laid upon this as a character. At the same time there is no doubt that, taken in connection with other details, it will often assist the determination of a species. After examining a large series of these birds, I have come to the conclusion that, as regards the wings, the following formulæ may be relied on: Wood Warbler, 2nd=4th; 3rd and 4th with
1 Mr. Blake-Knox subsequently corrected his statement, remarking that he had by mistake written second instead of third primary quill. The first primary is so rudimentary as almost to escape observation.
outer webs sloped off towards the extremity. Willow Warbler, 2nd=6th ; 3rd, 4th, and 5th sloped off. Chiff-chaff, 2nd=7th ; 3rd, 4th, 5th, and 6th sloped off.
The Wood Warbler is much greener on the back and whiter on the under parts than either of its congeners, and has a well-defined superciliary streak of sulphur-yellow, which, in the Willow Wren, is much shorter and paler. The legs of the Wood Warbler and Willow Wren are brownish flesh-colour, while those of the Chiff-chaff are dark brown. After the first moult, the young of all three species are much yellower in colour than their parents. Hence the mistake which Vieillot made in describing the young of P. trochilus as a distinct species under the name of flaviventris.
Although the majority of the Sylviida are fruit-eaters, the species now under considefation are almost entirely insectivorous ;' they are also more strictly arboreal in their habits,
1 Dr. Bree states that he has occasionally observed the Willow Wren taking currants from his trees.
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and as regards the character of their nests, they differr emarkably from other members of the Sylviida in building domed nests on or near the ground, instead of cup-shaped nests at a distance from it. The Yellow-billed Chiff-chaff——or Icterine Warbler, as it should now be called —however, forms an exception to the rule, as will be seen later. As these little birds make their appearance at a season when caterpillars and destructive larvæ begin to be troublesome, the good they do in ridding the young leaves and buds of these pests is incalculable. I have watched a Willow Wren picking the green aphis off a standard rose-tree, and have been as much astonished at the quantity which it consumed as at the rapidity of the consumption. The Wood Warbler is not nearly so sociable as either the Willow Warbler or the Chiff-chaff. It keeps to the tops of trees in woods and plantations, and seldom comes into gardens; hence it is not so often seen. Al
1 See Professor Newton's edition of Yarrell's “History of British Birds,” vol. i. p. 360.