Phylloscopus xanthodryas Swinhoe, Proc. Zool. Soc. (1863), 296;
Seebohm, Cat. Birds Brit. Mus. (1881), 5, 42.
Acanthopneuste xanthodryas Sharpe, Hand-List (1903), 4, 217;
McGregor and Worcester, Hand-List (1906), 90.
Apo (Celestino); Basilan (McGregor); Cagayancillo (McGregor);
Cebu (McGregor); Luzon (Celestino); Mindanao (Celestino); Palawan
(Everett). Mongolia, Japan, Kamtchatka, and the Kurile Islands;
in winter to southern China and Borneo.
"Spring plumage.--General color of the upper parts olive, slightly
yellower on the rump; eye-stripe well defined, narrow, yellowish white,
extending to the nape; lores and the feathers behind the eye to the
nape dark olive; wing-coverts olive, the median wing-coverts with
narrow, and the greater wing-coverts with broad yellowish white tips,
forming an obscure upper wing-bar and a conspicuous lower wing-bar;
quills brown, narrowly tipped with grayish white, the outside web edged
with green and emarginated as in the preceding species; tail-feathers
brown, the outside web margined with green, and the inside web with a
narrow well defined grayish white margin; general color of the under
parts greenish yellow, grayer on the breast and flanks; axillars,
under wing-coverts, and thighs pale yellow; inner margin of quills
grayish white. Bill acrocephaline; upper mandible dark brown, under
mandible pale; legs, feet, and claws brown; third and fourth primaries
longest; second primary usually intermediate in length between the
sixth and fifth, sometimes slightly shorter than the sixth; bastard
[first] primary measuring 12.7 to 15.2 mm. Length of wing, male,
72.1 to 68.5; female, 68.5 to 66; tail, male, 53.3 to 49.5; female,
49.5 to 45.7; culmen, 12.9 to 13.9; tarsus, 20.3.
"The changes of plumage in this species are similar to those of the
preceding species, but at all seasons of the year the general color of
the under parts is much paler in color in P. borealis (Blasius). The
smaller size and smaller first primary of the latter species serve,
however, to distinguish even birds of the year from the present
species, though they approach each other very closely." (Swinhoe.)
The yellow willow warbler is undoubtedly much rarer in the
Philippines than the next preceding species, but upon a careful
examination of available material I find it necessary to refer to
this species a number of specimens which were previously recorded as
A. borealis. These changes will be found in the list of localities
under each species.