Why these aerial birds are the only swifts capable of perching on branches

Nature · Published 3 October 2026 Swipe more like this →

In short: While true swifts are famously bound to the sky, the treeswift family possesses a unique anatomical advantage. Equipped with a nonreversible hind toe, these birds can land and rest on tree limbs. This distinct feature, alongside their elegant crests and soft plumage, sets them apart from their aerial cousins.

The treeswift family, known as Hemiprocnidae, consists of four species within the single genus Hemiprocne. These birds inhabit a vast geographical range stretching from the Indian subcontinent across Southeast Asia, through the Indonesian archipelago, and reaching as far as New Guinea and the Solomon Islands. Unlike their relatives in the Apodini tribe, which are eutaxic, treeswifts are diastataxic, meaning they lack a fifth secondary feather in their wings.

Physically, these birds measure between 15 and 30 cm in length. Their skeletal structure, specifically within the cranium, palate, and tarsus, differentiates them from true swifts. Beyond these internal traits, they are visually distinct due to their softer feathers, facial ornaments, and long, forked tails. Males are particularly notable for the iridescent plumage found on their mantles. While true swifts are incapable of perching, the treeswift uses its specialized hind toe to grip branches securely.

Habitat preferences vary significantly among the four species. The whiskered treeswift is highly specialized, remaining almost exclusively within primary forest canopies to hunt insects. In contrast, the grey-rumped treeswift is remarkably adaptable, thriving in environments ranging from coastal mangroves to dense hill forests. The crested treeswift occupies a middle ground, utilizing both humid and deciduous woodland areas. Despite these differences, all species share similar reproductive habits, with both parents collaborating to build a nest glued to a branch, where they lay a single white or grey egg.

Much of the treeswift's life remains a mystery to ornithologists. While it is known that chicks hatch covered in grey down and receive regurgitated food from their parents, specific details regarding their diet and incubation periods are still largely undocumented. The lack of comprehensive research into their prey selection highlights how much remains to be discovered about these agile, forest-dwelling birds.

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