The American Ornithological Society, or AOS (formerly the AOU), has just published the 60th supplement to its Checklist of North and Middle American Birds. This supplement, which used to be occasional, has become annual because new information is accruing fast and producing regular changes in our understanding of bird relationships.
As far as Missouri goes, the 60th supplement has produced no species splits or lumps that would increase or reduce our list. Our White-winged Scoter, however, has been split from two Old-World forms, called Velvet and Stejneger's Scoters, and that split has changed our species' scientific name to Melanitta deglandi. The English name for our species remains White-winged Scoter.
Just a few other names have been changed for other reasons. Band-rumped Storm-Petrel, an accidental vagrant in Missouri, has been moved to the genus Hydrobates along with many other storm-petrels; a new genus, Leiothlypis, has been established for the Tennessee, Orange-crowned, and Nashville Warblers and their close relatives; and the Common Ground-Dove has seen the hyphen removed from its name: Common Ground Dove (an odd minor adjustment reflecting the fact that not all birds called “ground doves” are of the same lineage).
Another type of rearrangement involves the order in which birds are listed within a family or genus, reflecting how closely related they are to other birds in the same group, as determined by the most recent genetic analysis. This "linear order" has been shifted in four groups that are relevant to us: the cuckoo family (Cuculidae), the Charadrius genus of plovers, the swallow family (Hirundinidae), and the family of North American sparrows and towhees (Passerellidae). The latter has undergone an extensive reordering among the species on our state list (28 of them).