Meet the “Tanabeak,” an Extremely Rare Tanager–Grosbeak  Hybrid

From the Winter 2023 issue of Living Bird magazine. Subscribe now.

If you’ve ever been confused about a bird call, take heart: sometimes even the birds themselves get a little mixed up.

In the spring of 2020, Steve Gosser was birding his local patch in western Pennsylvania when he heard the lilting, scratchy whistle of a Scarlet Tanager. But when he saw the singer swoop from its perch, he noted the bird was mostly black. When he finally got binoculars on it, he was surprised to see a bird that looked mostly like a Rose-breasted Grosbeak (albeit with a few strange attributes).

Gosser relayed his observations to the National Aviary in Pittsburgh, which sent ornithologists out to obtain a DNA sample and sound recordings of the mystery bird. The genetic and bioacoustics analyses, documented in research published in the journal Ecology and Evolution in August, identified the bird as a hybrid of a Scarlet Tana­ger father and Rose-breasted Grosbeak mother. The hybrid learned its tanager-like song from its father.

According to David Toews, lead author on the research, it’s the first-ever documented tanager-grosbeak hybrid. Toews, a biology professor at Penn State University and former Cornell Lab of Ornithology postdoctoral researcher, told USA Today that the bird is “affec­tionately most known as the ‘tanabeak,’ a mash-up of the tanager and grosbeak.”

“The interesting aspect … is that it’s between two relatively [evolutionarily] distant species,” says Leonardo Cam­pagna, assistant director of the Fuller Evolutionary Biology Program at the Cornell Lab.

The grosbeak and the tanager are in the same bird family (Cardinalidae) but in different genera—Pheucticus and Piranga, respectively. Previous genetic studies show that the two species diverged at least 10 million years ago. They also diverged in habitat preference; tanagers prefer deep woods habitat while the grosbeak is partial to forest edges.

Campagna says that even though evolution left the pieces in place for such unexpected, intergeneric hybrids, that’s usually the end of the line.

“Their mating systems are still com­patible to some degree, even though their genomes have diverged to the point that the hybrid itself is most likely sterile,” he says.