The black swift (Cypseloides niger) is a fascinating bird that intrigues ornithologists and bird enthusiasts alike with its speedy flight, aerial lifestyle, and mysterious migrations. Though widespread throughout western North America during the breeding season, black swifts are seldom seen, leading many to wonder just how rare these intriguing birds really are.
What is a black swift?
The black swift is a medium-sized aerial swift bird found along the Pacific Coast and in the Rocky Mountains. They have uniformly dark brownish-black plumage, long swept-back wings, and a slightly notched tail. Their bill is small but wide at the base.
Identification
Black swifts can be identified by their swift’s body shape and flight style, uniformly sooty black plumage, and wide white patches on the throat and chin. The white throat patches contrast sharply with the rest of the otherwise dark plumage.
In flight, black swifts have long, curved wings and look almost entirely black except for white undertail coverts. They have a stiff, shallow fluttering flight pattern with quick wingbeats.
Size and markings
Black swifts aremedium-sized swifts, with adults measuring 14–15.7 cm (5.5–6.2 in) long with wingspans of 33–40 cm (13–16 in). They weigh around 45–65 g (1.6–2.3 oz).
The adult’s plumage is entirely a dark sooty black, except for a large white patch on the chin and upper throat. The white throat patch is distinctive and contrasts sharply against the black breast and face.
The wings are uniformly dark blackish-brown. The tail is slightly notched at the tip. The bill and legs are black.
Voice
The call of the black swift is a clear, penetrating, ringing squeak or scream. It is given both during flight and while roosting or nesting on cliffs.
Other vocalizations include twittering noises and chip notes between mates and young. Clapping wing sounds are made during courtship flights.
Where do black swifts live?
The black swift has a relatively limited breeding range confined to western North America. Their breeding range extends from southeastern Alaska south to California and east to Montana, Wyoming, Colorado, and southwestern Canada.
Breeding range
The core of the black swift’s breeding range is along the Pacific Coast, from southern Alaska to northern California. They also breed inland in the mountains of British Columbia, Alberta, Washington, Oregon, and California.
Additional small breeding populations occur in the mountains of Idaho, western Montana, Wyoming, Utah, Colorado, and western Canada.
Winter range
The winter range of black swifts is not well understood since they are difficult to track outside the breeding season. Based on limited data, they are believed to migrate south to Central America and perhaps northern South America to overwinter.
Winter sightings occur around southern Mexico, Panama, and Venezuela. Some black swifts may remain along the Pacific Coast during the winter rather than migrating south.
Migration
Black swifts migrate long distances between their breeding and wintering grounds. Spring migration occurs from late April to early June as they return to nest sites. Southward fall migration happens earlier, from mid-July through September.
Migrating flocks fly high in the sky, even at altitudes over 3,000 meters (10,000 feet). Their migrations occur primarily at night.
Black swift habitat
Black swifts occupy a specialized niche breeding habitat, nesting exclusively on vertical cliff faces or near waterfalls in deep mountain canyons. The inaccessible rocky sites provide protection from predators and inclement weather.
Breeding habitat
Black swifts nest colonially on towering vertical cliffs, usually wet cliffs with waterfalls or overhanging dripping water. Western North American sites include sea cliffs along the Pacific Coast and mountainous canyon areas in national parks such as Yosemite and Glacier.
Preferred nesting cliffs are typically 100 meters (300 feet) tall or more. The water and spray help cement their bracket-like nests to the bare rock surface.
Non-breeding habitat
During migration and winter, black swifts use a wider variety of open foraging habitats. These include coastal areas, mountains, forest clearings, savannas, and openings over rivers and lakes from sea level to high elevations.
They roost on rocky cliffs and outcrops as well as tall trees and snags. At high altitudes, they even forage over mountaintops above treeline.
Black swift diet
The diet of black swifts consists entirely of insects captured during sustained foraging flights over open habitats. They eat both terrestrial and aquatic flying insects like flies, ants, beetles, mosquitoes, and emerging aquatic insects.
Aerial insectivores
Black swifts spend virtually their entire lives in flight as they hunt insects on the wing. They even drink by skimming the water surface and collect insect prey at the same time.
Their wide mouth and flexible lower jaw allow them to snatch up insects while flying with their beak open. They consume insects whole, swallowing them in flight.
Feeding behavior
Black swifts exhibit a feeding behavior called “flycatching” where they fly with their large mouth open to scoop up insects. They forage high in the air at altitudes typically 100–1,000 meters (300–3,000 feet) above the ground.
They patrol back and forth over one area or make large circular flights to hunt insects. Strong winds concentrate prey, making foraging easier. They often forage in groups that provide more sets of eyes to find swarms of flying insects.
Preferred foods
Preferred insect prey includes flies, mosquitoes, flying ants, beetles, mayflies, stoneflies, and other flying bugs. Aquatic insects like dragonflies and emerging midges are eaten over water surfaces.
On their wintering grounds, black swifts switch to eating more terrestrial insects like beetles, locusts, crickets, winged termites, and ants that fly in large swarms.
Black swift breeding and nesting
One of the black swift’s most intriguing traits is its highly specialized nesting habits. They choose towering vertical cliffs near water like sea cliffs or towering canyon walls along rivers and waterfalls.
Nest sites
Black swifts always nest on vertical rock faces, usually cliff faces with dripping water or behind waterfalls. Nest sites are typically 100 m (300 ft) high but can be up to 180 m (600 ft).
Preferred sites are caves, crevices, or ledges on perpetually wet rock faces often covered in mosses and lichens. Wet conditions help affix their nests to the rock surface.
Nest structure
The black swift’s nest is a shallow, bracket-like basket firmly cemented to a vertical rock surface. It is constructed from pine needles, small twigs, mosses, ferns, and lichens, bound together with thick saliva.
Nests average around 10 cm (4 in) across and 2 cm (0.8 in) deep. Unlike most bird nests, it has no cup and the eggs lay directly on the bare surface. The nests are reused for many years.
Eggs and young
The typical clutch size is 3 eggs that are incubated by both parents for 21-27 days. The eggs are white with brown speckles.
Chicks hatch with closed eyes and have slow development, not leaving the nest until they fledge at 6-7 weeks old. Nestlings initially sleep anchored to the nest with their claws to avoid falling.
Black swift population and conservation
Despite their small global population and specialized niche, black swifts remain fairly common and widespread in their native range. Overall populations appear stable, leading the IUCN to list them as a species of Least Concern.
Global population
The global population of black swifts is estimated at 120,000 to 350,000 individual birds. Their breeding range covers an area of about 4.5 million square kilometers (1.7 million square miles).
This is a relatively small total population for a bird species. However, black swifts remain locally common within their range due to their colonial nesting habits.
Population threats
There are no major threats to black swift populations currently. Their remote cliff nesting sites help protect them from most disturbance and habitat loss. Other potential threats include:
– Cliff development
– Disturbance like rock climbing near nests
– Pesticides reducing insect prey
– Extreme weather events
Conservation status
The black swift is assessed as a species of Least Concern on the IUCN Red List of Threatened Species. This indicates it is not currently vulnerable to extinction due to a relatively large and widespread population.
Partners in Flight estimate the global breeding population at 120,000 and rank black swifts overall as a Species of Continental Concern, meaning they warrant moderate conservation priority.
Fun facts about black swifts
Here are some fascinating tidbits about the unique and mysterious black swift:
– Black swifts spend virtually their entire life airborne, only landing to nest and roost on vertical cliffs. Even bathing and drinking occurs during brief dips at water surfaces while flying.
– Their scythe-like wings allow superb maneuverability in flight. They achieve speeds over 170 km/h (105 mph) in stoops and spiralling dives.
– Black swifts have the shortest legs of any swift relative to their body size. Their tiny legs and feet are used only for perching and clinging to vertical surfaces.
– Both parents help construct the nest over 50-70 days while roosting at the site. The nests contain special fungicidal chemicals that prevent rotting.
– Nestlings can withstand extreme dropping temperatures at high elevations thanks to a lowered metabolic rate and dense insulating down.
– Collisions with aircraft are an occasional mortality source since black swifts often forage at the same altitudes used by planes.
Conclusion
The black swift ranks as one of the most aerial of all bird species, an agile flier that lives almost perpetually on the wing. While elusive and difficult to spot, healthy populations still inhabit cliffs and canyons across western North America. Black swifts carved out a unique ecological niche – an aerial lifestyle hunting insects on the wing and nesting on towering inaccessible cliffs. There remains much to learn about their migrations and wintering ecology. But for now, populations appear secure, allowing bird lovers the continued chance to get glimpses of these acrobatic dark birds gracing the skies over the mountains of the West.