Chroicocephalus ridibundus (Linneaus 1766; 40cm long) is the extant black-headed gull. It was previously listed as the genus Larus and is a gregarious, opportunistic omnivore, usually seen close to the coast. Here gulls are descendants of kingfisher, basal to hummingbirds and stilts.

Eocypselus rowei (Ksepka et al. 2013; Eocene, 50 mya) was originally considered a swift and hummingbird ancestor. Here the swift, Apus, nests with Tyto, the owl and Falcothe falcon. Here Eocypselus rowei is a stilt (Himantopus) and hummingbird ancestor that nests with the gull, Chroicocephalus.

Eocypselus had a stout humerus, but not so stout as a hummingbird, relatively 2/3 the length and 1/3 deeper. Likewise in the hummingbird the radius/ulna is about 2/3 of the length in Eocypselus. The manus of the hummingbird is much longer than the combined length of the ulna and humerus, but not so in the more generalized and primitive Eocypselus rowei.

Ksepka DT, Clarke JA, Nesbitt SJ, Kulp FB and Grande L. 2013. Fossil evidence of wing shape in a stem relative of swifts and hummingbirds (Aves, Pan-Apodiformes). Proceedings of the Royal Society B: Biological Sciences 280 (1)

Linneaus C von 1766. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio duodecima, reformata. pp. 1–532. Holmiæ. (Salvius)

wiki/Black-headed_gull
wki/Eocypselus_rowei