Black-billed Gull vs Hartlaub's Gull

Black-billed Gull

Chroicocephalus bulleri

Medium230 gMarine

A healthy adult black-billed gull is typically 35–38 cm long, with a wingspan of 81–96 cm, and a weight of around 230g. The head, body, and parts of the wings are white, with silvery grey on the saddle and wings, as well as black edging on the wings. The gull also undergoes some seasonal color change. While typically black from February to June, the orbital ring is orange-red, red, or dark red the rest of the year. The legs, too, change from black to dark red and even bright red as the breeding season progresses, "possibly stimulated by presence of begging chicks and juveniles.

ID text from Wikipedia, CC BY-SA 4.0

Photo: Paul Davey edited by User:Tony Wills · Public domain

Hartlaub's Gull

Chroicocephalus hartlaubii

Medium288 gCoastal

Hartlaub's gull is 37–39 cm in length, with a wingspan of 89–92 cm and a weight of 235–340 g. It is a mainly white gull with a grey back and upperwings, black wingtips with conspicuous white "mirrors", and a dark red bill and legs. When breeding it has a very faint lavender grey hood, but otherwise has a plain white head. The sexes are similar. This species differs from the slightly larger grey-headed gull in its thinner, darker bill, deeper red legs, paler, plainer head, and dark eyes. It takes two years to reach maturity. Juvenile birds have a brown band across the wings.

ID text from Wikipedia, CC BY-SA 4.0

Photo: salsaboy on Flickr · CC BY 2.0

Photos and recordings are credited to their authors under the licence shown. Full profiles: Black-billed Gull and Hartlaub's Gull.