a1. Eye surrounded by a circle of white feathers; chin and throat, at
least, bright lemon-yellow; much smaller in size; wing less than 60 mm.
b1. Under parts not entirely yellow; sides of breast and of abdomen
whitish, ashy gray, or plumbeous.
c1. Median yellow line on breast and abdomen obsolete or wanting;
breast and abdomen white or very pale gray.
d1. Smaller; wing, 53 mm. or less; culmen from base, 12 or less;
forehead duller and less extensively yellow.
e1. Lighter and more yellow above; ear-coverts lighter and
more yellowish. ... meyeni (p. 615)
e2. Darker and less yellow above; ear-coverts darker and more
greenish olive.
f1. Smaller.
g1. Smaller, with no dusky shade under the
eye. ... whiteheadi (p. 615)
g2. Larger, with a dusky shade under the eye. ... vulcani
(p. 616)
f2. Larger. ... halconensis (p. 616)
d2. Larger; wing, about 58 mm.; culmen from base, 14; forehead
much brighter yellow. ... batanis (p. 616)
c2. Median yellow line on breast and abdomen well developed;
sides cinereous or ashy gray.
d1. Without a distinct blackish line under the eye; upper parts
more yellowish.
e1 Smaller; sides of breast lighter gray; forehead more
yellow. ... siquijorensis (p. 617)
e2. Larger; sides of breast darker gray; forehead less
yellow. ... boholensis (p. 617)
d2. With a distinct dusky line under eye; upper parts more
greenish.
e1. Lores yellow. ... everetti (p. 618)
e2. Lores dusky. ... basilanica (p. 618)
b2. Under parts entirely yellow.
c1. Greatest width of white eye-ring 3 mm. ... meyleri (p. 618)
c2. Greatest width of white eye-ring about 1.5 mm.
d1. Upper parts yellower; under parts brighter and yellower.
e1. Larger; wing, about 55 mm.; a distinct black line under
eye to base of bill. ... richmondi (p. 619)
e2. Smaller; wing, about 50 mm.; dusky line under eye less
distinct and not reaching the base of bill.
f1. General color duller. ... luzonica (p. 619)
f2. General color brighter; lores and frontal band brilliant
golden yellow. ... aureiloris (p. 619)
d2. Upper parts greener; under parts paler and, except on chin
and throat, slightly greener; eye-circle interrupted in front
by a small black spot. ... nigrorum (p. 620)
a2. Eye without a circle of white feathers; chin and fore throat very
pale cream-buff; wing more than 65 mm.
b1. Larger; bill more slender; front half of head
olive-green. ... goodfellowi (p. 620)
b2. Smaller; bill stouter; front half of head grayish
brown. ... malindangensis (p. 621)