If you have ever been deep within a South American rainforest and heard a strange, deep, resonant noise that sounded uncannily like a primate, you have encountered one of nature’s most effective auditory illusions. The source of this sound is not a monkey, but a bird known as the Capuchinbird. This large, passerine species produces a truly monkey-like call. The Capuchinbird is known for both its unusual appearance and its unique vocal performance.
The Capuchinbird
The Capuchinbird, formally known as Perissocephalus tricolor, is a large, thick-set bird belonging to the Cotingidae family. It can grow to approximately 40 centimeters in length and is one of the largest suboscine passerines. Its common name references the Capuchin order of monks, as its rich brown plumage resembles the hooded robes worn by friars.
This bird possesses a bare head covered in dull blue-gray skin, which creates a striking contrast with its cinnamon-brown body plumage. The dense feathers on the back of the head and neck are often raised during displays, forming a ruff that enhances the monk-like hooded appearance. While the bird lacks the fleshy neck wattle of its relatives, the male Capuchinbird has long, curled orange-rufous undertail-coverts conspicuously raised during courtship displays. The Capuchinbird is the only member of its genus, Perissocephalus. Females are similar in appearance to males but are slightly smaller.
Describing the Guttural Call and Geographic Range
The Capuchinbird is known for a deep, loud, and mechanical vocalization. It is frequently likened to the lowing of a calf, giving the species its alternative common name, the “Calfbird.” Others compare the sound to the distant roar of a chainsaw, a drawn-out guttural noise that echoes through the forest canopy.
The most common call is produced by the male during competitive mating displays, known as leks. To create this sound, the bird inflates air sacs on either side of its neck, storing air before forcing it out in a resonant “moo” or “grunt.” The volume and deep pitch often lead listeners to mistake it for a large mammal or primate. This vocalization attracts females and establishes dominance among displaying males.
The Capuchinbird is restricted to the humid tropical and subtropical forests of northeastern South America, generally north of the Amazon River. Its geographic range includes parts of Venezuela, Colombia, northern Brazil, and the Guianas: Suriname, Guyana, and French Guiana. The species is most often found in the upper canopy of tall trees, typically at elevations below 600 meters.
The Science Behind Avian Vocalization
The ability of the Capuchinbird to produce such a loud, resonant sound is rooted in the unique anatomy of the avian vocal organ. Birds do not possess a larynx with vocal cords like mammals; instead, they use a specialized structure called the syrinx. This organ is located lower in the airway, where the trachea branches into the two main bronchi leading to the lungs.
Sound is created when air flowing through the syrinx causes the membranes and labia within the organ to vibrate. The syrinx is a highly efficient sound producer, which is one reason birds can generate loud and complex vocalizations despite their small size. The low position of the syrinx allows the long neck to function as a resonant tube, helping to amplify and shape the sound before it exits the beak.
A unique feature of the avian syrinx is its potential for two independent sound sources, as the left and right sides of the organ can be innervated separately. This two-voice phenomenon allows some bird species to produce two distinct notes simultaneously. While the Capuchinbird’s call is a single, deep note, the anatomical complexity of the syrinx provides the mechanical foundation for its loud, guttural sound quality. The production of such species-specific calls requires a seamless synchronization of the syrinx muscles, respiration, and neural brain centers.