New Species of Hummingbird Discovered in the Bahamas

It can be hard to conceptualize evolution as an ongoing phenomenon. Its work is never observed within a generation, and rarely do we get the chance to newly witness its products. However, the work of Teresa Feo in the department of ecology and evolutionary biology at Yale has provided such an opportunity. Working alongside researchers from Cornell and UC Riverside, Feo has gathered enough evidence to separate two populations of hummingbirds into entirely distinct species.

Before Feo conducted her study, scientists had classified the Bahama woodstar, or Calliphax evelynae, into two subgroups of the same species: C. e. evelynae and C. e. lyrura. However, when Feo and colleagues observed behavior and took audio and high-speed video recordings of vocalizations and courtship displays, they found that the calls and songs of evelynae and lyrura differed significantly in frequency and pitch. The former had calls with a frequency of 5 to 6 kHz higher than those of lyrura. The courtship behavior of both birds appeared to be similar, but male evelynae and lyrura displayed distinctly different mating songs, which hummingbirds learn through interacting with their environment.

Until recently, scientists believed that C. lyrura and C. evelynae both belonged to one species of hummingbird. Research from Teresa Feo’s lab corrects this misconception. Image courtesy of New Jersey Birds.
Until recently, scientists believed that C. lyrura and C. evelynae both belonged to one species of hummingbird. Research from Teresa Feo’s lab corrects this misconception. Image courtesy of New Jersey Birds.

To collect further evidence to support her hunch — that these two groups are in fact two separate species — Feo continued her study at various natural history museums. She uncovered important morphological differences between the two birds. She found that lyrura males possess iridescent feathering on their forecrown, as well as the lyre-shaped tail feathers that have earned them their name. Both of these features are absent in the evelynae male, and are hypothesized to play a role in the differing courtship rituals of the hummingbirds.

Finally, genetic sequencing of the DNA of evelynae and lyrura suggested a mitochondrial pairwise divergence of about 2.7 percent, comparable to that observed between other closely related but separate species. Sequencing data allowed Feo and her team to place the divergence between the two groups as having occurred between 0.41 and 0.96 million years ago, an estimate that is further supported by shifts in sea level known to have occurred during this period that could have led to a geographic barrier between the two communities. Such data led scientists to identify evelynae and lyrura as monophyletic, meaning they share a common evolutionary ancestor.

With this evidence, Feo and her group were able to conclude that C. e. evelynae and C. e. lyrura are dissimilar enough to merit separate species status. The two species had originally been recognized as such due to the distinctive tail characteristics of lyrura, but were combined into one taxon in 1945.

One of the most difficult aspects of this study was collecting data on the birds’ courtship rituals. “Because there has been so little previous research on these hummingbirds, it was not clear when they were breeding and when during the year would be the best time to study them in the field,” Feo said. Once this breeding period was identified, however, the team could make detailed observations and recordings of the birds’ behavior.

Recognizing a population as a full species has important implications for future research in evolutionary biology and conservation. Potential future studies may further investigate the history of the divergence of these two species. There may be even more distinctions to uncover, even more assumptions to overturn with ongoing research. Moreover, Feo’s study gives tangibility to the concepts of divergence and adaptation, and it presents us with a beautiful reminder of the ongoing force of evolution.

Cover Image: Male Bahama woodstars are characterized by their brightly colored feathers. Image courtesy of Bruce Hallett.