- Larus delawarensis
L. 41–54 cm (16¼-21¼ in)
A fairly small white-headed gull, with gray back, thick bill, very narrow white crescents on back, a few white primary tips showing when standing, and pale yellow eye. Juveniles have contrasting white belly, pale rump with black tail band, and black primaries. They take three years to reach adult plumage.
- Mew Gull is slightly smaller with slightly darker back, dark eye, much thinner bill (sometimes with very thin ring), broad white crescents on back, and more white primary tips. Juveniles have uniform black-brown upperparts. Juvenile to 1st summer have brownish primaries.
- California Gull is larger with slightly darker back, dark eye, red and black marks on slightly longer bill. 2nd winter similar to 1st winter Ring-billed but back darker gray, dark eye, and blueish legs.
- Herring Gull is much larger Adult similar but with larger bill, pink legs, more extensive streaking on neck. 3rd winter similar to 1st winter Ring-billed but much larger with pink legs, and much more streaking to neck and head.
In breeding season found in Canada and the northern United States. Winters south to Mexico. Rare but regular vagrant to the UK with records annually. Accidental to France, Germany, The Netherlands, Portugal, Spain, Hungary, Italy, Sweden, Norway, Denmark, Morocco, South Africa, and Japan.
Lakes, rivers and the coast.
They build their nests on the ground. They tend to return to breed at the colony where they hatched. Once they have bred, they are likely to return to the same breeding spot each year, often nesting within a few meters of the last year's nest site. On the breeding grounds, females regularly form same-sex couples. Each member of the pair lays a clutch in the same nest resulting in 5–7-egg "superclutches" fertilized by an obliging male.
Includes insects, fish, grain, eggs, earthworms and rodents. Often forages at dump sites and landfills.
High-pitched and hoarse, with a wheezy, scratchy quality. The typical long-call is rather slow, beginning with a short kah followed by usually two longer louder, high pitched notes terminating in 5-7 brief, low pitched notes.
- Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2019. The eBird/Clements Checklist of Birds of the World: v2019. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
- Burger, J., Gochfeld, M. & Garcia, E.F.J. (2020). Ring-billed Gull (Larus delawarensis). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/53972 on 20 February 2020).
- Howell, S.N.G. and Dunn, J. (2007) A Reference Guide to the Gulls of the Americas. Peterson Field Guides, New York.
- Malling Olsen, K. & Larsson, H. (2003) Gulls of Europe, Asia and North America. Christopher Helm, London.
- Pollet, I. L., D. Shutler, J. W. Chardine, and J. P. Ryder (2012). Ring-billed Gull (Larus delawarensis), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.33
- BirdForum Opus contributors. (2021) Ring-billed Gull. In: BirdForum, the forum for wild birds and birding. Retrieved 22 September 2021 from https://www.birdforum.net/wiki/Ring-billed_Gull