The rainforest is home to a remarkable diversity of bird species, each with its own unique vocalizations. While most tropical birds sing beautiful, melodious songs, there is one bizarre species whose call sounds like a revving chainsaw. This strange bird is the white-throated sawbill, a little-known resident of remote rainforests in South America. In this article, we’ll explore why the sawbill makes such an odd, mechanical sound and how this unique call helps the bird survive in its dense forest home. Get ready to learn about one of the most distinct and unusual bird voices in the world!
What is the White-Throated Sawbill?
The white-throated sawbill (Psalidoprocne albiceps) is a small, inconspicuous bird that inhabits tropical rainforests from Nicaragua to the Amazon basin. It has mostly olive-green plumage, with a gray head and the distinctive white throat that gives the species its name. The sawbill measures around 13-15 cm long and weighs 20-30 grams. It can be hard to spot as it blends into the dense jungle vegetation, but its bizarre call gives its presence away.
Taxonomically, the white-throated sawbill is classified in the family Hirundinidae, making it a kind of swallow. It is closely related to other Neotropical sawbills in the genus Psalidoprocne, such as the black-capped sawbill and the rufous-thighed sawbill. Its genus name Psalidoprocne comes from the Ancient Greek words psalis, meaning “metal object”, and procne, meaning “swallow” – a reference to its metallic, mechanical-sounding call.
Habitat and Diet
The white-throated sawbill is found in tropical lowland rainforests and foothill forests up to 1200 meters in elevation. It prefers primary forest and avoids open areas or disturbed secondary growth. This specialized habitat niche limits its distribution and makes the species localized across its range.
It feeds on a diet of flying insects, catching prey on the wing. With its small, curved bill, the sawbill is adept at picking insects off leaves or catching them in midair. It often joins mixed-species foraging flocks to seek out concentrated patches of insects disturbed by flock activity.
Conservation Status
Due to its reliance on undisturbed primary rainforest, the white-throated sawbill is vulnerable to deforestation across its range. However, its total population size has not been quantified and is presumed to be large based on its wide distribution. For now, the IUCN Red List classifies the white-throated sawbill as a species of Least Concern. Ongoing habitat loss is a threat though, so its status merits monitoring.
The Chainsaw Call
The most distinctive feature of the white-throated sawbill is its loud, bizarre vocalization. When calling, it makes a whirring, mechanical sound that rises and falls in pitch. This call resembles the high-pitched revving of a chainsaw.
You can listen to its unique call here: [link to audio clip of sawbill call]
The sawbill’s chainsaw call is continuous and repetitive, lasting up to several minutes at a time. Both sexes vocalize in this manner. The species has an extensive repertoire – up to 16 different variations of its mechanical call have been documented. It also uses a short, simple chip note to communicate at close range with mates or rivals.
How and Why It Makes the Sound
But how does the sawbill produce this strange, unbirdlike sound? The mechanics of its vocalization are quite unusual.
When calling, the bird contracts its abdominal muscles and laryngeal muscles simultaneously to force air through its syrinx or voicebox. This coordinated muscle action causes tissues within the syrinx to vibrate rapidly, producing the characteristic whirring, saw-like sound.
The advantage of this physically demanding call is that it carries very far through the rainforest vegetation. The sawing sound can be heard up to 100 meters away by other sawbills. In the dense habitat, optimal sound transmission is crucial for territory defense and mate attraction.
Researchers believe the sawbill’s call evolved to take advantage of an empty acoustic niche. Most rainforest birds communicate with musical whistles and tones in the lower sound frequencies. By using a mechanically-produced call in the higher frequency range, the sawbill avoids overlap or interference with other bird sounds. This helps its call stand out to other members of its own species.
Ecology and Behavior
The white-throated sawbill lives either solitary or in pairs year-round. It vigorously defends a breeding territory of approximately one hectare in size. Both partners engage in calling duets to proclaim territory ownership and challenge intruders. The pair bond between mates appears to be long-term.
Breeding
The sawbill’s breeding biology reflects its specialized rainforest niche. It nests in tree cavities, either natural hollows or old woodpecker holes. Cavity selection offers protection from predators and harsh weather. Pairs may excavate their own nest holes in softer dead wood, using their sharp bills as chisels.
Nesting occurs during the rainy season from May to August. The female lays a clutch of two white eggs with brown speckling. She incubates the eggs alone while being fed by her mate. After a 16-18 day incubation, the helpless nestlings hatch. Both parents share brooding and feeding duties until the young fledge around three weeks later.
Roosting
When not actively breeding, sawbills roost communally in cavities. Up to 50 birds may pack together into a single large hollow for safety at night. These roosts are thought to contain extended family groups along with unrelated birds. Communal roosting offers protection through shared vigilance against nocturnal predators.
Migration
The white-throated sawbill is generally considered non-migratory across most of its range. However, some populations in Central America exhibit seasonal movements tracking food availability. Northern sawbills may migrate south up to 500 km between Nicaragua and Costa Rica after breeding.
Evolutionary History
The sawbill’s evolutionary lineage reflects South America’s unique geographic history. Molecular studies indicate that sawbills likely originated in Africa and arrived in South America around 25 million years ago. At the time, South America was an isolated continent with many endemic species.
After formation of the Isthmus of Panama connected North and South America 3 million years ago, a wave of North American bird groups invaded South America. Sawbills were already adapted to tropical forests and likely outcompeted many northern species trying to colonize the same niche. This isolation from northern competitors may have allowed the unusual chainsaw call to develop and persist.
Today, sawbills remain a relic of South America’s distinct evolutionary past. Their saw-like call represents a unique behavioral adaptation in birds worldwide.
Conclusion
The peculiar call of the white-throated sawbill stands out as one of the neotropics’ most distinctive sounds. What bird behaves like a power tool turned up to full throttle? This obscure rainforest resident inhabits one of the most specialized niches of any bird species. Its bizarre vocalization allows it to stake out breeding territory and attract mates in dense habitat where visibility is near zero. Next time you’re in a tropical rainforest, stop and listen – you may be able to pick out the distinctive whirring of a sawbill! Learning about obscure species like this gives us a greater appreciation of nature’s boundless diversity.
