Ornithologists have discovered a new species of tinamou living in the montane forests of the Serra do Divisor, 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 comprises the small forest tinamous and is the most diverse within the family Tinamidae, with 21 recognized species,” said lead author Dr. Luis Morais from the Universidade Federal do Rio de Janeiro and his colleagues.
“Despite its diversity, Tinamus remains one of the least-studied avian groups in the Neotropics, largely due to its cryptic habits and the inaccessibility of the dense forest habitats it occupies.”
“The western Amazon harbors the greatest diversity of Tinamus species co-occurring within the same region.”
“However, few studies have addressed the taxonomy of tinamous in this area, leaving several important questions unresolved.”
The researchers first recorded a distinctive vocalization of the new species in 2021 in the understory of the Serra do Divisor, an isolated mountain complex located on the border between Brazil and Peru.
“The song resembled those of Tinamus, yet no species could be confidently identified at the time, and no visual confirmation was obtained,” they explained.
“Comparisons with all Tinamus vocalizations known from the region, alongside consultations with ornithologists experienced in Amazonian avifauna, failed to produce a conclusive match.”
“The song appeared unlike any known tinamou vocalization, raising the hypothesis that it might represent an undescribed form.”
In 2024, the scientists succeeded in attracting two individuals using a digitally synthesized playback from earlier recordings, obtaining excellent views and photographs of one bird.
“During the field expedition to Serra do Divisor National Park, five recognized species of Tinamus were detected: Tinamus bartletti, Tinamus cinereus, Tinamus soui, Tinamus strigulosus, and Tinamus variegatus,” they said.
“All these species were recorded in lowland forests and along the lower montane slopes.”
“In contrast, the only representative of the genus encountered in the higher elevations of the mountains, above 250 m, were the specimens representative of the taxon here assumed as an undescribed species, exhibiting an unique combination of plumage coloration and vocal structure, which we formally name as: Tinamus resonans (common name is the slaty-masked tinamou).”
Over the course of ten independent encounters at eight sites across the mountainous region of the Serra do Divisor, the authors confidently identified at least 15 distinct individuals.
“Considering the total extent of suitable habitat within the defined elevational range (63,302 ha), we estimate a preliminary population size of approximately 2,106 individuals in the Serra do Divisor mountain complex,” they said.
Tinamus resonans is distinguished by a unique combination of plumage pattern, vocal repertoire, and ecological characteristics, including a conspicuous dark slate facial mask, vivid rufous-cinnamon underparts, and a uniform brownish-gray back.
“This species differs from all other Tinamidae by presenting, at least in females (the three individuals whose sex could be determined were female), a distinctive dark slate-colored crown, which extends into a prominent stripe down the hindneck and into the post-ocular region, forming a conspicuous facial mask,” the ornithologists said.
The vocalizations of Tinamus resonans are remarkable, consisting of long and powerful songs that echo strikingly across the steep montane slopes, producing a characteristic resonant effect.
“Tinamus resonans was recorded vocalizing spontaneously during the late afternoon and dusk, between 17:40 and 18:30 local time,” they researchers said.
“Its song is loud and carries over long distances, but undergoes marked acoustic diffusion along the steep slopes of the Serra, which alters the temporal structure of the song due to echo.”
“When confronted directly, individuals showed no avoidance behavior and appeared remarkably tame, seemingly failing to recognize humans as potential predators.”
“In addition, individuals were observed crossing open areas of understory slowly and without signs of vigilance, a behavior contrasting with the typically wary responses of other tinamous.”
“Between vocal responses, birds were also observed foraging on the forest floor, probing and overturning leaf litter with the bill in search of food items.”
According to the scientists, Tinamus resonans may be highly vulnerable to climate change and to proposed infrastructure projects in Brazil.
“The discovery of Tinamus resonans highlights the biological uniqueness of the Serra do Divisor, reinforces its status as a center of montane endemism, and underscores the critical importance of maintaining its long-term conservation,” they concluded.
Their paper was published on December 2, 2025 in the 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
