WALL-BIRD—WARBLER 1019 
M. rau (by some mistakenly called M. campestris), which, though 
very generally distributed throughout the country, is much less 
numerous than the Pied Wagtail, and more addicted to wet 
* meadows ; but, just as I. lugubris is regarded by some as a local 
form of the more widely-ranging JZ. alba, so does M. raii hold the 
same relation to M. flava, the Blue-headed Wagtail, which has a 
very extensive distribution in the Old World, and even crosses the 
Pacific to Alaska, presenting also a great number of varieties or 
races (most of them treated by Dr. Sharpe as real species) differing 
from each other chiefly, if not solely, in the colour of the head, a 
character which in this section can hardly be deemed specific, while 
their geographical range intersects and inosculates in a most 
puzzling manner. Credit is due to the author just named for the 
enormous trouble he has taken, after study of a vast series of speci- 
mens, to clear up the questions herein involved ; but it will probably 
be long before ornithologists can agree on many of the disputed 
points, and it is certain that the last word has by no means been 
spoken concerning them. 
WALL-BIRD, a common local name of the Spotted FLYCATCHER 
(p. 274); WALL-CREEPER see under TREE-CREEPER (p. 986). 
WARBLER, the name bestowed in 1773 by Pennant (Gen. Birds, 
p. 35) on the birds removed, in 1769, by Scopoli from the Linnzan 
genus Motacilla (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 Eng- 
lish technical writers as the equivalent of Sylvia, and consequently 
generally applied to all members of the Family Sylviidx thereon 
raised, which has since been so much subdivided as to include a vast 
number of genera, while species almost innumerable have from time 
to time been referred to it. 
Until recently ornithologists had come to agree pretty well as to 
which forms should be considered to belong to the Family Sylviidz, 
—the “American Warblers” (Mniotiltidx), to be presently con- 
sidered, being therefrom segregated ; but some writers, seeing the 
difficulty of separating the remainder from the Zurdidx (THRUSH), 
tried to get over it by proposing to erect an intermediate Family 
for the WHEATEAR and some similar forms, under the name Sazi- 
colidx.| But the affinity, seeming or real, to the Turdidx does not 
1 Tn truth the difficulty was thereby doubled, for, if it was before hard to dis- 
tinguish between Sylvitde and Turdidx, it has since become harder to dis- 
tinguish on the one hand between Sylviidz and Sawicolidxe, and on the other 
between Saxicolide and Turdidx. The confusion thus caused is chiefly due to 
the adoption in a more or less modified form of the views put forth by Sundevall 
in 1872, and revised by him in 1874 (cf Inrropucrion). Yor him, however, it is 
