Two Birds, One Species

There is an ancient and venerable tradition of describing the sexes of a single kind of bird as two different species: Think of the Williamson sapsucker or the black-throated blue warbler, in which females and males are visually so different that even now, long after the puzzle was solved, it can be hard to think of the two as “the same.”

The like confusion reigned for decades in the case of a widespread tropical American bird, too, the common and familiar barred antshrike, found from Mexico to Paraguay. The gorgeous zebra-striped male—and only the male—was described in 1764 by Linnaeus, who named it Lanius doliatus, the “barred shrike.” 

It took 28 years for the equally striking but very different female to make it into print, in a catalogue of South American bird specimens donated to the Paris Society for Natural History by Jean Baptiste Leblond; the cataloguers assigned her the scientific name Lanius ferrugineus. John Latham, with access to a specimen sent to England by William Bullock, renamed this female Lanius rubiginosus, again in reference to her overall rusty plumage. 

Not until 1805 were two and two put together. The Spanish general Félix de Azara was posted to South America in 1781, where he was to take part in a survey establishing the border between the colonies of Spain and the colonies of Portugal. His Portuguese counterpart never arrived, however, and Azara spent the rest of the eighteenth century in Paraguay, studying the plants and animals while he patiently waited to be recalled to Spain. During his 20 years in America, Azara made the acquaintance of well more than 300 species of birds, among them the “batara listado,” both sexes of which are thoroughly described in his 1805 study of the birds of Paraguay. 

And how did he know that these two so different birds were of the same species? Azara was the first European ever to observe the nest of any antshrike, and he noted carefully that the streaked white eggs were incubated in turn by a black-and-white individual and a rusty one, leaving no doubt that these were in fact the male and female of what we now know as the barred antshrike.

Mystery solved.

These two barred antshrikes were photographed in the course of my scouting for the VENT October 21–28 visit to Panama’s Canopy Tower. Join us!