Look for the Traill’s Flycatcher and you will be disappointed – in the 1970s this species was split into the Willow Flycatcher and the Alder Flycatcher. While the two species may look the same, their vocalizations are different and they have largely separate ranges. Today, researchers are uncovering other “new” species through genetic testing and song analysis, hoping to find cryptic species, those birds which may look the same, but are reproductively separate.
A recently described cryptic species, the Tokara Leaf Warbler (Phylloscopus tokaraensis), was previously thought to be the Ijima’s Leaf Warbler (Phylloscopus ijimae), a rare and vulnerable species on Japan’s Izu and Tokara Islands. A research team analyzed the genome of birds from the islands and museum collections and learned that the birds on the Tokara Islands are genetically different from those on the Izu Islands, findings that matched a careful analysis of the birds’ songs. New research analyzing genetics, mitochondrial sequences, and vocalizations suggesting the two lineages split roughly 2.8 to 3.2 million years ago and show no sign of interbreeding, despite seasonal movements that can bring them into contact with each other.
This work is especially important for island species which have geographic and gene pool limitations that create small and vulnerable bird populations. Splitting off the new Tokara Leaf Warbler from the Ijima’s Leaf Warbler means even smaller, distinct, and vulnerable populations which need to be understood and protected before either, or both, suffer extinction.