How to identify the Brown-headed Gull

To correctly identify the Brown-headed Gull (Chroicocephalus brunnicephalus), 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

41-45 cm (16-18 in)

Wingspan

105-115 cm (41-45 in)

Weight

350-500 g (12-18 oz)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Breeding adults have a chocolate-brown head and neck, a white eye-crescent, a white body with a pale grey back and upper wings, black primary wingtips with white 'mirrors', and a deep reddish-orange bill and legs. Non-breeding adults have a white head with dusky smudges behind the eye and on the nape, a dark bill, and duller legs. The underparts are white.

2. 2

   Beak shape

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

   Moderately long, slender, and slightly decurved, deep reddish-orange in breeding plumage, darker in non-breeding plumage and juveniles.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Pale yellow, often with a white crescent around the eye that is more pronounced in breeding adults.

4. 4

   Leg color

   Leg and foot color.

   Deep reddish-orange in breeding adults, duller orange to reddish-brown in non-breeding adults, and yellowish-orange in juveniles.

5. 5

   Distinguishing features

   Standout features that separate this species.

   Breeding plumage: uniform brown head (not black), white eye-crescents, pale grey mantle, and black primary tips with white mirrors. Non-breeding plumage: distinctive dark ear spot and a less defined dark smudge on the nape.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   Juveniles have a mottled brown-and-white head and neck, brownish-grey upperparts with dark centers to the feathers giving a scaly appearance, a dark band on the tail, and yellowish-orange legs and a dark-tipped bill. They acquire adult-like plumage over two years.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   Pronounced seasonal changes between breeding and non-breeding plumage. The most notable change is the head coloration, transitioning from chocolate-brown in breeding season to white with dark smudges in non-breeding season.

8. 8

   Sexual dimorphism

   How males and females differ.

   Males and females are similar in appearance, though males can be slightly larger on average.

Key field marks

• Breeding Head Color. Look for the uniform chocolate-brown head and neck, a key differentiator from other similar gulls.
• Eye-Crescent. Note the prominent white crescent above and below the eye, especially visible against the brown head.
• Wingtip Pattern. Observe the extensive black primary tips with two distinct white 'mirrors' (patches) on the outer primaries, a good field mark in flight.
• Bill and Leg Color. In breeding adults, the deep reddish-orange bill and legs are distinctive. In non-breeding, the dark bill and duller legs, combined with head pattern, aid identification.
• Non-breeding Head Pattern. In winter, look for a pure white head with a distinct dark ear spot and often a dusky smudge on the nape, rather than a full dark hood.

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