There hasn’t been a mass extinction in the intervening years. The wood-warbler species are all still there, but filed under a different genus name, Setophaga. Instead, there has been a major shift in how ornithologists sort and classify bird species, and the genus name Dendroica was a casualty.

Decisions about how North American bird species are classified and what is and is not considered a species are made every summer by a special committee of the American Ornithological Society. An AOS committee bases its judgments on the best available science. But the science is rapidly expanding. Like many other branches of biology, ornithologists are trying to make sense of a flood of new information flowing from the latest advances in genome mapping. Today, avian geneticists can dive deep into genomes to unveil the molecular differences underlying variation between birds.





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