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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. . 3-0 in. . o-7in.
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 Ben
nett, 1875, PP- 5^, 57, ke f°und a l°ng 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 distinct-ion.1 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 formulae 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 fiaviventris.
Although the majority of the Sylviidce are fruit-eaters, the species now under consideration are almost entirely insectivorous;1 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.
and as regards the character of their nests, they differr emarkably from other members of the Sylviidce 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 called1—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 larvae 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.
though not rare, it is somewhat local, and in the British Islands, it appears, is confined exclusively to England and the south of Scotland. Mr. Thompson has included it with hesitation amongst the birds of Ireland; for although the description given to him of certain birds and eggs seemed to apply to this species, it was stated that the nest which contained the eggs was lined with feathers. Now, the Willow Wren invariably makes use of feathers for this purpose, but the Wood Warbler does not. The nest of the latter is composed entirely of dry grass and leaves, occasionally mixed with a little moss; and although I have sometimes found horsehair inside, I do not remember to have seen or heard of an instance in which any feathers were employed. The eggs, five or six in number, are white, closely freckled over with reddish brown.
Mr. Blake-Knox, a well-known naturalist, resident in the county of Dublin, says (" Zoologist," 1866, p. 300), "I tried very hard this year to add the Wood Wren to our Dublin