A novel species of tinamou has been identified by ornithologists, inhabiting the mountainous woodlands of the Serra do Divisor in western Amazonia, Brazil.
An individual of Tinamus resonans at Morro Queimado, Serra do Divisor National Park, Mâncio Lima, Acre, Brazil. Image credit: Luis A. Morais.
“The genus Tinamus encompasses the smaller forest-dwelling tinamous and represents the most diverse group within the Tinamidae family, featuring 21 established species,” remarked lead author Dr. Luis Morais of the Universidade Federal do Rio de Janeiro, alongside his research associates.
“Despite its considerable diversity, Tinamus remains among the least explored avian groups in the Neotropics. This is largely attributable to their elusive nature and the challenging inaccessibility of the dense forest environments they frequent.”
“The western Amazon region is home to the most significant concentration of co-occurring Tinamus species within a single geographical area.”
“However, scant research has been dedicated to the taxonomy of tinamous in this particular zone, leaving several critical questions open to resolution.”
In 2021, the researchers initially documented a distinctive vocalization from the new species within the undergrowth of the Serra do Divisor, a secluded mountain range situated on the frontier between Brazil and Peru.
“The call bore resemblance to those of other Tinamus species, yet at the time, no species could be unequivocally identified, nor was any visual confirmation secured,” they elaborated.
“Comparative analyses with all known Tinamus vocalizations from the area, coupled with insights from ornithologists with extensive expertise in Amazonian birdlife, did not yield a definitive match.”
“The song appeared dissimilar to any previously recorded tinamou vocalization, prompting speculation that it might represent an unidentified form.”
Subsequently, in 2024, the scientific team successfully attracted two specimens by employing a digitally synthesized playback derived from earlier recordings, thereby obtaining exceptional visual observation and photographic documentation of one individual.
“During our fieldwork in Serra do Divisor National Park, we identified five established Tinamus species: namely, Tinamus bartletti, Tinamus cinereus, Tinamus soui, Tinamus strigulosus, and Tinamus variegatus,” they reported.
“These species were all observed in lowland forests and along the lower elevations of the mountain slopes.”
“In contrast, the sole representative of the genus found at higher elevations within the mountains, exceeding 250 meters, comprised individuals indicative of what we now propose as an undescribed species. These specimens exhibited a unique combination of plumage coloration and vocal characteristics, which we formally designate as: Tinamus resonans (with the common name being the slaty-masked tinamou).”
Across ten separate observations spanning eight distinct locations within the mountainous terrain of the Serra do Divisor, the investigators reliably identified a minimum of 15 individual birds.
“Considering the total area of suitable habitat within the delineated elevational range (63,302 hectares), we project an initial population estimate of approximately 2,106 individuals within the Serra do Divisor mountain complex,” they stated.
The Tinamus resonans is characterized by a singular juxtaposition of its plumage pattern, vocal repertoire, and ecological traits. These include a prominent dark slate facial mask, vibrant rufous-cinnamon underparts, and a uniformly brownish-gray dorsal surface.
“This species is differentiated from all other members of the Tinamidae family by exhibiting, at least in females (the three individuals sexed were female), a distinct dark slate-colored crown. This coloration extends into a pronounced stripe down the hindneck and into the region behind the eyes, thereby forming a noticeable facial mask,” the ornithologists elucidated.
The vocalizations produced by Tinamus resonans are noteworthy, comprising lengthy and powerful songs that create a striking echo effect across the steep montane inclines, resulting in a characteristic resonant quality.
“We recorded Tinamus resonans vocalizing spontaneously during the late afternoon and twilight hours, specifically between 17:40 and 18:30 local time,” the researchers noted.
“Its song is quite loud and carries considerable distances, yet it experiences significant acoustic diffusion along the steep slopes of the Serra, which consequently modifies the temporal structure of the song due to reverberation.”
“When directly approached, these individuals displayed no evasive maneuvers and appeared remarkably docile, seemingly failing to perceive humans as potential threats.”
“Furthermore, individuals were observed traversing open areas of undergrowth at a leisurely pace and without any indications of alertness, a behavior that starkly contrasts with the typically cautious reactions observed in other tinamous.”
“In the intervals between vocal responses, birds were also observed engaging in foraging activities on the forest floor, using their bills to probe and overturn leaf litter in their quest for sustenance.”
According to the scientific findings, Tinamus resonans may face considerable vulnerability from climate change and from proposed infrastructure developments within Brazil.
“The discovery of Tinamus resonans serves to underscore the exceptional biological distinctiveness of the Serra do Divisor, reinforces its status as a key region for montane endemism, and highlights the paramount importance of its sustained conservation efforts,” they concluded.
Their research article was officially published on December 2, 2025, in the esteemed scientific journal Zootaxa.
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Luis A. Morais et al. 2025. A new species of Tinamus (Aves: Tinamiformes) from the western Amazon, Brazil. Zootaxa 5725 (2); doi: 10.11646/zootaxa.5725.2.6
