Time to Reorder the Field Guides

The "Tern" Jessica Leber--Did you know that parrots and passerines are closely related to falcons? Don’t sweat it if you didn’t—neither did the world’s ornithologists, until this week. Now, a new genetics study published in the journal Science has shaken several bird groups off their perches on the avian tree of life. 

The evolutionary relationships among birds have long been difficult for experts to tease apart. That’s because, very early in their history, a rapid explosion of avian diversity created most of the distinctly different bird types we know today. As a result, owls look very different than doves, which are unlike parrots, and there are few in-betweens alive to help scientists figure out how all were once related. These diverse groups branched so quickly (say within a few million years) that it’s also hard for scientists to use fossils to agree upon their ancestral linkages.

That’s where molecular biologists can step in to offer some concrete clarity—they can look at DNA sequences to check for common heritage in seemingly disparate bird groups. The current study, conducted by a collaboration of scientists under a National Science Foundation-funded umbrella called the Early Bird Project, is the largest and most extensive look at the evolutionary genetics of birds ever, according to a press release. The group compared DNA from 19 spots on the chromosome of each of 169 bird species, which represent every group alive today. 

What they found overturned much of their previous conventional wisdom. For example, scientists have thought that shorebirds were the ancient ancestors of all modern birds; however, the new data show that this is not the case.

What the DNA does illustrate is that birds which act or live similarly aren’t necessarily two of a feather. Instead, birds may have adapted to diverse environments and adopted similar habits at several instances during their history. For example: Some water birds, like flamingos and tropicbirds, are not all closely related to other aquatic birds.  Similarly, doves and sandgrouses, both land-dwellers, are unrelated to other terrestrial birds. Along the same lines, falcons aren’t very genetically similar to other birds of prey like hawks and eagles (though they do have close kinship with parrots). And all of those pretty hummingbirds that hover during the day—they share a close common ancestor with the plain, nocturnal nightjar. Even the evolution of flight is questioned since Tinamous, which fly, were unexpectedly grouped with the flightless group Struthioniformes, which include ostriches, cassowaries, and emus. 

While so many who read Audubon work hard to preserve the amazing diversity of birds on this planet, it's fascinating to stop and think about the 100 million years or so of evolution it's taken to bring us to this point today.

For more on this study see an analysis by ornithologist and blogger “GrrlScientist” here.