This was the most common small gull in the harbor. This is an adult in winter plumage which lacks the dark hood. Black-headed Gull ranges across Eurasia but is replaced in North America by the similar Bonaparte's Gull. Interestingly, it is the Bonaparte's Gull who actually has a black head in breeding plumage while the Black-headed Gull's head is decidedly brown in breeding plumage. In 2007 SACC moved this species along with other small hooded gulls from Larus into the genus Chroicocephalus in an effort to keep Larus monophyletic. This classification has been adopted by most authors with the notable exception of HBW and Birdlife International. These gulls bear a strong resemblance to Brown-hooded Gull (Chroicocephalus maculipennis) which ranges along the coasts of Southern South America. In fact, the two were considered conspecific by Hellmayr. Brown-hooded has a slightly darker mantle, narrower dark subterminal band on its primaries, more dark at the bases of its outermost primaries, and distinct white primary tips cf. Black-headed.
