How to identify the Black-and-white Warbler

To correctly identify the Black-and-white Warbler (Mniotilta varia), 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

11-13 cm (4.3-5.1 in)

Wingspan

20-22 cm (7.9-8.7 in)

Weight

8-15 g (0.28-0.53 oz)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Adults are boldly striped black and white over their entire body. Males have more extensive black on the throat and cheeks, particularly during breeding season. Females and immatures are duller, with less black on the throat and flanks, often appearing more grayish-white where males are pure white.

2. 2

   Beak shape

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

   Slender, pointed, and slightly decurved black bill, adapted for probing bark crevices.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Dark brown.

4. 4

   Leg color

   Leg and foot color.

   Dark gray to black.

5. 5

   Distinguishing features

   Standout features that separate this species.

   Overall black and white striped appearance, especially on the head, back, and underparts. Two prominent white wing bars. Distinctive foraging behavior of creeping up and down tree trunks and branches.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   Juveniles are similar to adult females but are generally duller, with a buffy wash on the underparts and less distinct streaking. Their black markings are often more brownish-black.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   Males are brightest and most distinctly marked during the breeding season. In non-breeding plumage, males become slightly duller, with some white mottling on the black throat, resembling females more closely. Females show little seasonal change, remaining consistently duller than breeding males.

8. 8

   Sexual dimorphism

   How males and females differ.

   Males in breeding plumage have a solid black throat and cheek patch, and heavier black streaking on the flanks. Females have a white throat and less distinct streaking on the flanks, often appearing grayish on the sides of the neck and breast. Non-breeding males resemble females but retain some black on the throat.

Key field marks

• Plumage Pattern. Look for the distinctive black and white stripes covering the entire body, including the head, back, and underparts. Males have a solid black throat and cheek patch in breeding season.
• Foraging Behavior. Observe its unique 'creeping' behavior, moving up and down tree trunks and large branches like a nuthatch, rather than flitting through foliage like most warblers.
• Wing Bars. Note the two prominent white wing bars on dark wings, which are consistent across sexes and ages.
• Song. Listen for its high-pitched, reedy, and accelerating 'wee-see, wee-see, wee-see' song, which can be a key identifier, especially when the bird is high in the canopy.
• Size and Shape. It's a small, slender warbler with a relatively long tail and a thin, pointed bill.

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