New bird species discovered through scientific collections
Natural history collections are full of surprises, with scientists updating what is known about different species and uncovering new ones.
Dr. Matthew Halley, Assistant Curator of Birds, is the lead author of a recently-published paper that splits the Slaty-backed Nightingale-Thrush (Catharus fuscater) into seven different species and four subspecies — including a newly-described species from eastern Panamá: the Darién Nightingale-thrush (Catharus arcanus).
Photo of Matthew Halley by Jenna McCullough
These genetically distinct populations live in secluded mountain rainforests in Central and South America and began to diverge from each other nearly three million years ago.
The species look very similar to an untrained eye. To document their differences, Dr. Halley and his team sequenced DNA from multiple populations, studied physical features like plumage color, iris color and bill color, and analyzed differences in their vocalizations.
Dr. Halley shared the findings on his Twitter (now X) account. Read on for a summary, along with some of the figures from the paper:
This figure shows the geographic distribution of the C. [fuscater] complex in Central and South America. Lines point to type localities. The variation in shapes denote sampling locations for different molecular data. Shape size is correlated with the number of samples (1–3).
The C. fuscater complex (Turdidae) is composed of several disjunct populations that inhabit cloudy mountain rainforests, ranging from Costa Rica to Bolivia. These birds are diabolically shy and more often heard than seen. Their song is a series of sweet, musical whistles.
The research identified 10 genetically distinct populations that have been evolving independently for multiple glacial cycles. Molecular clock suggests most lineages diverged in early Pleistocene / late Pliocene— ancient lineages with independent evolutionary trajectories.
This figure shows taxonomic variation in the structure of ‘punctuation calls’, visualized in RavenPro 1.5 (Cornell University), recognizing three groups based on shared acoustic structure: (Type 1) pulsed/rippling: C. [f.] hellmayri, Undescribed 1 (now C. arcanus), C. [f.] mirabilis; (Type 2) long/sinuous: C. [f.] sanctaemartae, C. [f.] fuscater, C. [f.] berplepschi; (Type 3) short/simple: Undescribed 2 (now C. o. tenebris), C. [f.] opertaneus, Undescribed 3 (now C. b. nebulus), C. [f.] mentalis.
Populations were divergent in the acoustic structure of three different call types, which are presumed to be innately acquired (i.e., not learned), and there were subtle differences among populations in song structure, which is presumably learned.
This image is a side view of polychromatic adult plumages in C. [f.] mentalis (from left to right): 1, FMNH 433742, a ‘grey’ male with enlarged testes; 2, FMNH 433738, a ‘brown’ male with enlarged testes; 3, FMNH 364458, a ‘brown’ male with testes not enlarged; 4, FMNH 433740, an adult female with an enlarged ovary. Adults of both colour types (FMNH 433742, 433738) were collected at the same site in November
Halley traveled to the American Museum of Natural History, the National Museum of Natural History and Carnegie Museum of Natural History to study their C. fuscater specimens, and borrowed specimens from the Field Museum, LSU Museum of Natural Science, and the Academy of Natural Sciences of Drexel University, bringing them to the museum to look at sexual and age-related differences in plumage color.
This image shows ventral and dorsal views of the adult male plumages in C. b. berlepschi, C. b. caniceps, C. o. tenebris ssp. nov., C. b. nebulus ssp. nov., and C. mentalis.
With a large sample of study skins assembled under one light source (flat panel LED), subtle differences between populations, difficult to appreciate in the field, became easier to notice — Halley scored this variation by comparing the specimens to published color standards.
The taxonomic revision splits the C. [fuscater] complex into seven species, of which one is newly described, and four subspecies, of which two are newly described (C. opertaneus tenebris, C. berlepschi nebulus). New English names were proposed for each species. The seven species are:
Talamanca Nightingale-thrush (Catharus hellmayri) – monotypic – Northern mountains of Costa Rica (Rincón de la Vieja, Miravalles, Tenorio) to west-central Panama (Parque Nacional Santa Fé, Veraguas). (Photo: alchetron.com)
Darién Nightingale-thrush (Catharus arcanus, sp. nov.) – monotypic – E Panama, endemic to Serranía de Majé and Serranía del Darién, from Cerro Azul in the west, to Cerro Tacarcuna in the east
Pirre Nightingale-thrush (Catharus mirabilis) – monotypic – Endemic to Cerro Pirre, Darién province, E Panama. (Photo: ML 242929041)
Cordilleran Nightingale-thrush (Catharus fuscater) – polytypic – (1) C. f. sanctaemartae, endemic to Sierra Nevada de Santa Marta, NE Colombia; (2) C. f. fuscater, Sierra de Perijá of Venezuela, N and E Andes of Colombia and Venezuela. (Photo: ML 206115721)
Trans-Andean Nightingale-thrush (Catharus berlepschi) – polytypic – (1) C. b. berlepschi, W Andes in Ecuador; (2) C. b. caniceps, W Andes in Ecuador, S to NW Peru; (3) C. b. nebulus, ssp. nov., E Peruvian Andes. (Photo: ML 38468741)
Antioquia Nightingale-thrush (Catharus opertaneus) – polytypic – (1) C. o. opertaneus, NW and Central Andes in Colombia, S to Napo, Ecuador; (2) C. o. tenebris, ssp. nov., Río Chinchipe watershed of N Peru and SE Ecuador
Cochabamba Nightingale-thrush (Catharus mentalis) – monotypic – S Peru, east of the Río Apurímac, E to Santa Cruz, Bolivia
Note: Monotypic species are not divided into subspecies. Polytypic species can be divided into at least two subspecies.
Halley, M. R., Catanach, T. A., Klicka, J., and J. D. Weckstein. 2023. Integrative taxonomy reveals hidden diversity in the Catharus fuscater (Passeriformes: Turdidae) complex in Central and South America. Zoological Journal of the Linnean Society zlad031. LINK
If you are unable to access the paper and would like a copy, please email Matt Halley.
Learn more about Dr. Halley’s research projects and publications on his website.