This bird, photographed at Sweetwater Wetlands in Tucson, Arizona, was formerly known as Common Moorhen. Now, following a determination by the American Ornithologists' Union that it is separate from the Common Moorhen of Eurasia, its name is Common Gallinule. Photo by Lois Manowitz

The American Ornithologists’ Union, the body responsible for English bird names and scientific nomenclature, has again paved the way for a new edition of your favorite field guide.

Recognizing a recent series of spectacular sightings made by birdwatchers, it added seven birds to the roster of species known to occur in the United States:

• White-chinned Petrel, recorded off California in 2009 and Maine in 2010

• Bare-throated Tiger-Heron, spotted at Bentsen-Rio Grande Valley State Park, Texas, in December 2009

• Sungrebe, photographed at Bosque del Apache NWR, New Mexico, in 2008

• Amazon Kingfisher, found in Laredo, Texas, in January 2010

• Gray-collared Becard, seen in Cave Creek Canyon, Arizona, in June 2009

• Brown-backed Solitaire, found in Miller and Ramsey Canyons, Arizona, in 2009

• Red-legged Thrush, which delighted viewers at Melbourne Beach, Florida, in May 2010.

The AOU also split two North American species — Common Gallinule (above) and Snowy Plover — from their Eurasian counterparts (Common Moorhen and Kentish Plover, respectively); it split Mexican Jay from Transvolcanic Jay of central Mexico; and it split Yellow-throated Warbler from Bahama Warbler, a resident of the Bahamas.

And in a move that reflects rapid advances in our understanding of the evolutionary relationships of birds, taxonomists thoroughly reorganized the wood-warbler family tree.

The changes affect groupings of wood-warblers in the AOU’s Check-list of North American Birds. Forty species were transferred from one genus to another. Six genera — including familiar Parula, Dendroica, and Wilsonia — were done away with. And species and genera were arranged in a new sequence.

Four species with orange or white on their tails — American Redstart (left, photo by Paul Kusmin), Northern Parula, Tropical Parula, and Hooded Warbler — were added to the large group of warblers formerly known as Dendroica, and all the birds in the group were assigned to the redstart’s genus, Setophaga.

MacGillivray’s, Mourning, and Kentucky Warblers were grouped with Common Yellowthroat and Gray-crowned Yellowthroat (a species found in Mexico and Central America), leaving larger Connecticut as the lone member of Oporornis.

And long- and plain-tailed Canada and Wilson’s Warblers were grouped with Red-faced Warbler in the genus Cardellina.

The classification committee considered but did not approve splitting either Mountain Chickadee or Yellow-rumped Warbler. But comments posted on the AOU website suggest that committee members may reconsider after more genetic data is published.

The AOU also denied a request by author and tour leader Steve N.G. Howell to rename the Winter and Pacific Wrens. (The species were split from each other, and from Eurasian Wren, in 2010.) Arguing that the name Pacific Wren hadn’t caught on with birders, he had proposed the names Eastern and Western Winter Wren.

The changes raised the number of birds recognized in North America from 2,070 to 2,078. The checklist update appears in the July issue of The Auk and is available as a downloadable PDF from the AOU website. —Chuck Hagner, Editor

Read how the Yellow-rumped Warbler could be split into as many as four species.

Read about checklist changes made by the AOU last year.