A Tale of One Tiny Bird's Twisty Road to Protection

Ever wonder whether biologists' constant renaming and reshuffling of organisms from one taxonomical pigeonhole to another has any actual importance in the real world?

You could ask the wrentit. A tiny bird that lives in stands of chaparral along the California coast, the wrentit was just reassigned from one family of birds to another -- and as a result, it's now protected under one of America's oldest environmental laws: the Migratory Bird Treaty Act of 1918 (MBTA).

How'd this happen? It has to do with a group of scientists who discuss bird taxonomy in the U.S., and how the agency responsible for enforcing the MBTA follows those scientists' lead in determining which birds are protected by the law.

The American Ornithologists' Union (AOU) is a century-old group of people who appreciate and study birds, including scientists and amateur birders. It publishes a well-regarded peer-reviewed journal, The Auk, and a longer-form journal called Ornithological Monographs, as well as a number of books. But the Checklist of North and Middle American Birds is likely the most influential of the AOU's publications, and it's widely accepted as the go-to source for the most current scientific thinking on bird taxonomy.

The U.S. Fish and Wildlife Service, which is charged with enforcing the MBTA, uses the Checklist as its main authority in determining which bird species are covered by the law. In addition to migratory birds, the MBTA protects a number of non-migratory birds that are members of specifically listed families. Taxonomists often disagree over which family a species properly belongs to, so USFWS has to pick a primary authority for their determinations, and the AOU Checklist is a good one: it's authoritative and cautious.

The Checklist is updated fairly frequently, and there's a rigorous procedure for doing so: scientists can make formal proposals to the AOU Committee on Classification and Nomenclature to change the status of a bird species, subspecies, or other population. The Committee reviews those proposals and if they're approved (a 2/3 vote's needed) then the changes are made in an annual update to the Checklist.

In the teaser to this article I referred to the idea that these changes may not bear much relevance to the "real world." It's a common gripe made by those who try to keep up with name changes, but the process is supremely relevant to anyone interested in knowing how all us living things are related to each other. Taxonomic categories reflect, as closely as we can determine, which groups of organisms share common ancestors, and how those common ancestors were themselves related to each other. As we learn more about how we all evolved, through DNA analysis and other means, we learn that some of our old notions about how each of us fit into the big evolutionary jigsaw puzzle need to be updated. When that happens, taxonomy often needs to change as well.

The wrentit, Chamaea fasciata, is part of a larger group of birds that has perplexed ornithologists for some time. In recent years it's been bounced between five different closely related families depending on which ornithologist is writing about them. Until recently the AOU Checklist put the wrentit in the family Timaliidae, commonly known as Old World babblers, a huge group of small songbirds similar to warblers and thrushes. Most Old world babblers are native to Eurasia, Africa, and Australasia, with an especially diverse number of species in the Indian subcontinent. But the Timaliidae is what taxonomists call a "wastebin" family: scientists have long classified birds as Old World babblers when they don't quite fit into other, better-defined families.

Nothing attracts the attention of career-building taxonomists like a wastebin taxon: there's science to be done untangling the actual relationships of species that have been assigned to such a group. And the Timaliids are no exception. Ornithologists have been busy over the last few years sifting through the Old World babblers to see whether they can make sense of the family. Consensus is still off in the distance somewhere. But in 2010, enough evidence had come in on that the wrentit was not all that closely related to Old World babblers that the AOU moved it to the family Sylviidae, or Old World warblers.

Sylviidae used to be a wastebin family as well, with more than 70 genera containing over 400 species. But it had previously been reformed to make more sense according to the evolutionary logic of taxonomy. The Old World warblers now mainly include Asian species, with a few in Africa and Europe and (now) one on the West Coast of North America: the wrentit.

Wrentits don't migrate. They range from the Columbia River in the Pacific Northwest to San Quintin in Baja California. Adult wrentits pretty much stay in their home territories, living in shrubland and chaparral and eating insects and other invertebrates that they find beneath the poison oak, coyote brush, and similar shrubs that they prefer to inhabit. In California wrentits inhabit both the coastal mountains and shrubby areas in interior mountains like the Peninsular Ranges and the Sierra Nevada. They prefer large stands of undisturbed chaparral: in places where there's been development, the wrentit tends to decline in numbers.

If it migrated, the wrentit would automatically, as a bird native to the U.S., be protected by the MBTA. That would make it illegal to hunt, pursue, capture, sell, or kill, and to possess their eggs, feathers and body parts, without a waiver from USFWS. The MBTA is pretty much the baseline for bird protection in the U.S.; bird species that aren't protected by any other federal or state law often find themselves under the MBTA's umbrella. It's a crucial law for just that reason. It protects more than 1,000 birds whom other laws often neglect.

But the wrentit isn't migratory. So whether or not the species enjoys MBTA protection depends on whether it belongs to a family that's specifically included in the law's protection.

The family Timaliidae, which the wrentits used to belong to, is not protected under the MBTA. The wrentit's new family Sylviidae is. And so when the AOU moved the wrentits into the Sylviidae in 2010, it was pretty much a foregone conclusion that USFWS -- usually at least a couple years behind on these things -- would amend its MBTA rules to include the wrentit.

And that happened last Friday, in a USFWS ruling published in the Federal Register. USFWS also added 22 other species to its MBTA list in the ruling. Six were already-protected subspecies newly given full species status. Eleven were birds newly established to show up as vagrants in the U.S., including appearances in California by the Parkinson's petrel, which usually hangs out more in the neighborhood of New Zealand, and the Swallow-tailed gull, a Galapagos-area seabird. Both have now been granted the MBTA's protection as a reward for having gotten terribly lost.

What does all this mean? There hasn't been any change in the wrentit, but as a result of a taxonomical technicality it now enjoys the protection of a law that is, when USFWS decides to enforce it, a fairly stringent environmental protection law. Once the ruling becomes effective on December 1, big development projects that threaten to disrupt California's chaparral habitat have one more wildlife species to consider, and one more set of permits to get before they can start cutting down coyote brush.

Not a bad result from a group of scientists considering what might seem forbiddingly wonky data.