Introduction

In 1840, when John J. Audubon penned his description of the Solitary Vireo for his book, Birds of America , the bird was believed to be one species. The Cassin’s and Plumbeous Vireos were still unknown to science, so there was good reason to think there was only one species. With the advent of genetic sequencing and, most recently, DNA barcoding, we know that the Solitary Vireo’s identity is not very solitary: it is, in fact, at least three species hiding under one name.  Today, in San Diego County and throughout its range, we find in the former Solitary Vireo the Cassin’s, Blue-headed, and Plumbeous Vireos.  The phenomenon of look-alike species, such as our three vireos, is known as a cryptic species complex.

A cryptic species complex is a group of organisms that satisfy the biological definition of species—that is, they are reproductively isolated from each other—but whose morphology is very similar, and in some cases, virtually identical.

Species identification has long challenged scientists.  Certain species that may look the same to the naked eye, and even share similar behaviors, such as a set of yellow butterflies, may turn out on closer inspection to be more than one species.  In fact, DNA barcoding demonstrates that look-alikes may be two, ten, or as many as dozens of different species.

How can we know what we observe? DNA barcoding is among the most important tools allowing us to identify and distinguish species.  DNA barcodes supplement traditional taxonomic methods and open exciting new understanding of just how complex and diverse is the natural world.  Reading nature—bioliteracy—is at hand, with the realization of cryptic species: like discovering a new book on a shelf you thought you already read through, or new lighting revealing hidden shades of color for the first time.  Global biodiversity shows its richness even as we strive to protect the habitats that sustain it.

Eric Palola, Executive Director, Guanacaste Dry Forest Conservation Fund and Joseph Rossano, Artist.

John James Audubon Reference

See John James Audubon in his Birds of America from an 1840 "First Octavo Edition" of Audubon's complete seven volume text: http://web4.audubon.org/bird/BOA/F20_G1b.html.

Learn More...

Read more about the Plumbeous,  Cassin's or Blue-headed Vireo (PDF files) in  San Diego County an entries from our Museum's San Diego Bird Atlas. 

Explore the rest of BOLD with the support of Ontario Genomics Institute.  

Photography credits:

Blue-headed Vireo by Thomas A. Blackman
Plumbeous Vireo by Vic Murayama

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