20-7-2024 HUSAVIK, ICELAND - BLACK HEADED GULL (Chroicocephalus ridibundus)

The black-headed gull (Chroicocephalus ridibundus) is a small gull that breeds in much of the Palearctic including Europe and also in coastal eastern Canada. Most of the population is migratory and winters further south, but some birds reside in the milder westernmost areas of Europe. The species also occurs in smaller numbers in northeastern North America, where it was formerly known as the common black-headed gull.

The black-headed gull was previously placed in the genus Larus but in agreement with the NACC and SACC, and based on Pons et al. (Pons, J.-M.., A. Hassanin, and P.-A. Crochet. 2005. "Phylogenetic relationships within the Laridae" (Charadriiformes: Aves) inferred from mitochondrial markers, "Molecular Phylogenetics and Evolution" 37: 686-699) and earlier references, extensive changes to the taxonomy of gulls was undertaken and many species of gull were removed from the genus Larus, including the black-headed gull 

The black-headed gull displays a variety of compelling behaviours and adaptations. Some of these include removing eggshells from the nest after hatching, begging co-ordination between siblings, differences between sexes, conspecific brood parasitism, and extra-pair paternity. They are an overwintering species, found in a variety of different habitats.

This gull is 37–44 cm (14+1⁄2–17+1⁄2 in) long with a 94–110 cm (37–43+1⁄2 in) wingspan and weighs 190–400 g (6+3⁄4–14+1⁄8 oz).

This species takes two years to reach maturity. First-year birds have a black terminal tail band, more dark areas in the wings, and, in summer, a less fully developed dark hood. Like most gulls, black-headed gulls are long-lived birds, with a maximum age of at least 32.9 years recorded in the wild, in addition to an anecdote now believed of dubious authenticity regarding a 63-year-old bird.