According to a press release this week from the Cornell Lab of Ornithology, some of the tiniest birds in North America can help answer some of the largest questions in the biological sciences: how do species evolve? In a new study, Density-dependent diversification in North American wood warblers, Dan Rabosky and Irby Lovette examined 25 species of Dendroica wood warblers from North America using DNA analyses and a mathematical model that shows how closely related species divide up their environment (think Cerulean Warblers in the treetops and Black-throated Blue Warblers lower down).

It turns out that species diversification happens in a relatively quick burst: of the 5 million years that Dendroica species have been around, most have been around for 4 million of those years.

The authors needed the mathematical modeling because the fossil record is simply insufficient to provide a chronological record of when and where such tiny birds changed over such a relatively short time span. As Rabosky says in the press release, “the vast majority of biodiversity on this planet that we need to explain doesn’t have a fossil record. But just by using species that are alive today, and looking at their DNA, we can see the signal of an early explosion of species millions of years ago.”