Taxonomy
The taxonomy of gulls is confused by their widespread distribution zones of hybridization leading to geneflow. Some have traditionally been considered ring species, but recent evidence suggests that this assumption is questionable. Until recently, most gulls were placed in the genus Larus, but this arrangement is now known to be polyphyletic, leading to the resurrection of the genera Ichthyaetus, Chroicocephalus, Leucophaeus, Saundersilarus and Hydrocoloeus. Some English names refer to species complexes within the group:
- Large white-headed gull is used to describe the 18 or so Herring Gull-like species from California Gull to Lesser Black-backed Gull in the taxonomic list below.
- White-winged gull is used to describe the 4 pale-winged, High Arctic-breeding taxa within the former group; these are Iceland Gull, Glaucous Gull, Thayer's Gull, and Kumlien's Gull.
Hybridisation between species of gull occurs quite frequently, although to varying degrees depending on the species involved (see Hybridisation in gulls). The taxonomy of the large white-headed gulls is particularly complicated.
In common usage, members of various gull species are often referred to as sea gulls or seagulls; however, "seagull" is a layperson's term that is not used by most ornithologists and biologists . This name is used informally to refer to a common local species or all gulls in general, and has no fixed taxonomic meaning. In common usage, gull-like seabirds which are not technically gulls (e.g. albatrosses, fulmars, kittiwakes, terns and skuas) may also be referred to as 'seagulls' by the layperson.
The American Ornithologists' Union combines Sternidae, Stercorariidae, and Rhynchopidae as subfamilies in the family Laridae, but recent research indicates that this is incorrect.
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