Calls are used for communication between pairs while flying or perched. Treeswifts calls have been described as a squeal, with a few syllables grouped together to form a disyllabic or trisyllabic call. Treeswifts can also raise the crest of feathers on their head, a gesture assumed to be a form of communication. Large eyes help treeswifts navigate while feeding at dusk and dawn.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
The IUCN lists no treeswifts as endangered or vulnerable and none are listed by CITES. Because treeswifts use forest edge they may benefit to some degree from disturbance and fragmentation. However, they do rely on large tracts of contiguous forest and could be adversely affected if too much of their habitat is lost. Grey-rumped treeswift (Hemiprocne longipennis) numbers are thought to be declining as a result of increases in hunting and pesticide use (that decreases the number of available prey). It is also important to note that little is known about the four species of treeswifts, so it may be difficult to accurately assess the status of their populations.
Treeswifts are in the order Apodiformes. There are three families within this order: Hemiprocnidae (treeswifts), Apodidae (true swifts) and Trochilidae (hummingbirds). Treeswifts also belong to the suborder Apodi. There is one genus of treeswifts and 4 species. The four species are: grey-rumped treeswift (Hemiprocne longipennis), crested treeswift (Hemiprocne coronata), whiskered treeswift (Hemiprocne comata) and moustached treeswift (Hemiprocne mystacea).
Treeswifts are insectivores and catch the majority of their prey while flying. Unlike their close relatives, true swifts, treeswifts are able to perch, are not very social and have more ornate coloring (some species have bold white striping on their heads). Treeswifts also have crests on their heads and are easy to identify when perched because of their long crossed wing-tips and deeply forked tail.
They are monogamous and both males and females provide parental care. In-flight copulation has been recorded. Although they occur throughout much of the Oriental region, little is known about the Hemiprocnidae family.
There are no known adverse affects of treeswifts on humans.
Treeswifts are hunted as a food source for humans. Because they are insectivores, treeswifts are also important agents in pest control.
Positive Impacts: food ; controls pest population
As insectivores, treeswifts affect insect populations throughout their range.
Treeswifts are insectivores, they catch their prey while in-flight (hawking) or they glean insects from foliage. Treeswifts drink by flying near the surface of water with an open mouth. They are often crepuscular (feed at dawn or dusk). Treeswifts hunt opportunistically and frequently feed on Hymenoptera (bees, wasps and ants), Diptera (true flies), Hemiptera (true bugs), Isoptera (termites) and Coleoptera (beetles).
Treeswifts will not travel as far to feed as true swifts (Apodidae) and instead of doing all hunting on the wing, they will perch in an open place and dart from their perch to catch aerial insects. The birds’ large gape and manoeuvrable flight help them to catch their prey. They also have bristles around their mouths that may help them trap insects as they fly.
Primary Diet: carnivore (Insectivore )
Treeswifts are found throughout the Oriental Region (East to the Solomon Islands) and in some of the Australian region.
Biogeographic Regions: oriental (Native ); australian (Native )
Treeswifts are tropical terrestrial forest birds and are found in evergreen forest, deciduous forest and mature mangrove stands. They require stretches of continuous forest, but can make use of areas with breaks in the canopy (for example, roads and rivers) and some edge habitat. They are found from lower elevations up to 2000 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: forest
The lifespan of treeswifts is unknown; however, most small birds live only two to five years.
Grey-rumped (Hemiprocne longipennis) and crested (Hemiprocne coronata) treeswifts have glossy, primarily grey plumage with a forehead crest that is 2.5 to 3 cm tall. Both males and females have crests that they raise when perched. Both whiskered treeswifts (Hemiprocne comata), the smallest member of the genus and moustached treeswifts (Hemiprocne mystacea), the largest treeswifts, have a slight crest and a bold face pattern with white stripes along the side of the head. Sexes of all species may differ in coloration on the head.
Treeswifts have a short bill and a broad gape and are typically 15 to 31 cm long. They have large eyes that may help them forage into late evening when the light is low. Unlike true swifts (Apodidae), treeswifts are able to perch, they are easy to identify when perched because of their long crossed wing-tips and deeply forked tail. Their long outer streamers allow for increased manoeuvrability while foraging. Like typical swifts, treeswifts have a long manus and primary feathers.
Juveniles have cryptic head and body plumage that they lose during the first moult after fledging.
Sexual Dimorphism: sexes colored or patterned differently; ornamentation
Other Physical Features: endothermic ; bilateral symmetry
The only confirmed predators of treeswifts are Asian falconets (Microhierax), although there are almost certainly additional predators (snakes (Serpentes), for example, are likely predators). Nest placement on the end of a thin branch is thought to aid treeswifts in the detection of climbing predators. Nests and juvenile plumage are cryptic. Groups of treeswifts will mob predators as they approach.
Anti-predator Adaptations: cryptic
Treeswifts are monogamous; both males and females provide parental care. Breeding pairs will defend nest sites against intruders. No male display flights have been recorded.
Mating System: monogamous
Treeswifts have a long breeding season that occurs during the spring and summer. Both males and females take part in nest building; nests are made of bark, feathers and bryophyte held together with saliva. Nests are half-saucer shaped and from 25 to 40 mm in diameter (just big enough to hold one egg) they are usually placed on exposed branches in the forest canopy (4 to 30 m in height). Because nests are so small adults must perch on a branch and straddle the nest while incubating; nestlings outgrow the nest rapidly and will move out of the nest and perch on a nearby branch while waiting to be fed.
Both in-flight copulation and copulation on a perch have been recorded in treeswifts. Clutch size is one and eggs are plain white or pale grey. Crested treeswift (Hemiprocne coronata) eggs are 23 to 26 by 15.5 to 19 mm, grey-rumped treeswift (Hemiprocne longipennis) eggs are 23 to 24.5 by 17 to 18 mm, whiskered treeswift (Hemiprocne comata) eggs are 12 by 15 mm and moustached treeswift (Hemiprocne mystacea) eggs are 30 by 20mm. Females spend two to three times more time incubating than males. There are no exact measurements of incubation and nestling periods. However, during one observation of whiskered swifts chicks hatched on or before day 21, fledged on day 28 and continued to be fed by adults for another three weeks. Estimates for moustached swifts suggest that incubation and nesting periods together last more than 60 days. Young chicks are brooded for an unknown period of time after hatching.
Chicks are altricial with grey skin and some grey down. Juvenile plumage is cryptic and is lost during moult after fledging.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Both male and female treeswifts are involved in parental care, although females incubate two to three times more than males. Treeswift chicks are altricial. The length of the nestling period is not known, but chicks may be fed for three weeks after fledging. Adults brood chicks for an unknown amount of time after hatching. Chicks are fed “food balls” containing insects.
Parental Investment: altricial ; male parental care ; female parental care