How to identify the Yellow-browed Warbler

To correctly identify the Yellow-browed Warbler (Phylloscopus humei), check each of these features. Birds can be tricky: habit, habitat, and call often confirm a sighting that a single photo cannot.

Size at a glance

Length

9-10 cm

Wingspan

15-16 cm

Weight

5-9 g

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Upperparts are dull greenish-grey, underparts off-white to pale greyish-white. It features a prominent yellowish-white supercilium (eyebrow stripe) that extends behind the eye, a dark eye-stripe, and a pale central crown stripe (though often indistinct or absent in some individuals). It has two distinct yellowish-white wing-bars, with the lower bar being longer and brighter. The tertial edges are pale, creating a panel effect on the folded wing. Rump and uppertail coverts are slightly brighter green than the back.

2. 2

   Beak shape

   Shape and color of the bill: a key field mark.

   Small, fine, and pointed, dark horn-colored with a paler base to the lower mandible.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Dark brown.

4. 4

   Leg color

   Leg and foot color.

   Dark grey to blackish-brown.

5. 5

   Distinguishing features

   Standout features that separate this species.

   Key features include the prominent yellowish supercilium, two distinct yellowish wing-bars, and often a pale central crown stripe. Its overall coloration is duller and greyer than the similar Pallas's Leaf Warbler, lacking the bright yellow rump and more vibrant green tones.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   Juveniles resemble adults but may have slightly fresher plumage and sometimes a slightly more yellowish wash to the underparts, though differences are subtle and not reliable for field identification.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   No significant seasonal plumage changes. The plumage may appear slightly duller and more worn towards the end of the breeding season before the post-breeding molt.

8. 8

   Sexual dimorphism

   How males and females differ.

   None; males and females are identical in plumage.

Key field marks

• Size and Shape. Very small, active warbler with a relatively short tail and a rather flat head profile.
• Plumage - Upperparts. Dull greenish-grey back, often appearing quite plain.
• Plumage - Underparts. Off-white to pale greyish-white, lacking strong yellow tones.
• Head Pattern. Prominent yellowish-white supercilium (eyebrow stripe) extending well behind the eye, contrasting with a dark eye-stripe. A pale central crown stripe may be present but is often indistinct or absent.
• Wing-bars. Two distinct yellowish-white wing-bars. The lower (greater covert) bar is typically longer and brighter than the upper (median covert) bar.
• Tertial Edges. Pale edges to the tertial feathers create a noticeable pale panel on the folded wing.
• Leg Color. Dark grey to blackish-brown legs, which can appear quite dark in the field.
• Vocalization. The most reliable identification feature for P. humei is its distinctive, sharp, single-note 'chup' or 'chip' call. This is crucial for distinguishing it from the Common Yellow-browed Warbler (P. inornatus).
• Behavior. Constantly active, flitting through foliage, often hovering briefly to pick insects.

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