The Belding’s Yellowthroat is a marsh-loving warbler endemic to the Baja California Peninsula in Mexico. It differs from the more northern Common Yellowthroat (Geothlypis trichas) in being extensively yellow below, and showing a yellow surround to the black mask instead of a white one. The Belding’s Yellowthroat is otherwise a typical yellowthroat, living in and breeding in fresh-water marsh. It takes Scirpus reeds or Typha cattail, and presumably only requires that emergent vegetation be thick and relatively tall. As it is found in a largely desert region of the world, its distribution is spotty and fragmented; this is a common species where the right habitat exists, but in world terms it is a relatively rare species. Quite curiously molecular work shows it to be reasonably distinct, but sister to the western populations of the Common Yellowthroat. In fact it is more closely related to the western Common Yellowthroat, than the western Common is to the eastern Common! This suggests that there may be a species level distinction between eastern and western Common Yellowthroats, or something equally interesting in the history of the Belding’s Yellowthroat. Molecular data, voice, and plumage all argue strongly that the Belding’s Yellowthroat is a good species. It is Endangered.