Leaf Warblers and Allies: Family Phylloscopidae

Leaf Warblers are a relatively new family of birds that was once placed as a genus within the Old World Warbler family. Old World warblers and leaf warblers share very similar ancestry, appearance and habits. They are small songbirds that live in forested regions and survive on a diet of insects which they catch while flying. Like their Old World Warbler relatives, these birds are generally a dull greenish-yellow color and have a small, pointed beak to catch insects. So why, you ask do these birds deserve their own family? Well the answer lies within the realm of genetic drift and biogeography.

DNA Never Lies

Our ability to study organisms based on their DNA has changed the way that we organize species taxonomically. Its often a frustrating task and yields interesting, albeit annoying results. By using any other means of organization, the Leaf Warblers would be placed in the Old World Warbler family, but their DNA tells us that they are different enough to be placed in a different family altogether.

The coolest part about studying an organism's DNA is that it forces us to recognize the tiniest differences in the way similar organisms are different. It turns out that the difference between the Leaf Warblers and Old World Warblers is that Leaf Warblers have chosen a slightly different habitat, which changed the types of prey they were able to hunt, and also the means in which they could hunt them. These small changes allowed them to evolve physically, to better exploit their new habitat.

This is a very common process that illustrates genetic drift beautifully. When a population of organisms becomes isolated in a new habitat, certain genes can become more accentuated if it benefits that organism in its new habitat. Natural selection takes over, and soon enough a new species is produced.