Christmas Island Swiftlet
Collocalia natalis
Generic-looking “white-bellied swiftlet”, but fortunately the only regular one on Christmas Island; migratory House and Pacific Swifts are larger, with bright white rump patches. Note the pale belly, dusky throat, weakly forked tail, and glossy dark upperparts, all traits typical of the genus Collocalia. Forages in swift, bat-like flight above a range of habitats on Christmas Island, sometimes forming loose flocks.
Identification
The Christmas Island swiftlet is a small swiftlet some 9–11 cm (3.5–4.3 in) in length. It is mainly glossy blue-black or green-black above, with dark grey underparts relieved by a prominent white belly and vent.
Taxonomy
The Christmas Island swiftlet was described by the English naturalist Joseph Lister in 1889 with the scientific name Collocalia esculenta natalis. It has usually been considered a subspecies of the glossy swiftlet (Collocalia esculenta). However, in 2008 the taxonomists Les Christidis and Walter Boles treated the swiftlet as a subspecies of the cave swiftlet (Collocalia linchi). It was raised to species status based on a detailed analysis of the swiftlets in the genus Collocalia published in 2017.
- Scientific name
- Collocalia natalis
- Authority
- Lister, 1889
- Order
- Apodiformes
- Family
- Apodidae
- Genus
- Collocalia
Range and habitat
This swiftlet is restricted to the 135 km2 Christmas Island where it is commonly seen in large numbers in flight above the tropical rainforest that covers 75% of the island, as well as over other terrestrial habitats there. It nests mainly in caves in the limestone cliffs surrounding the island.
Behavior
The swiftlet breeds deep in caves, in almost total darkness. It builds a small cup-shaped nest for its clutch of two eggs, high up on the cave wall and often sheltered by a stalactite. The nests are made of dried palm fibres and lichen and are cemented to the cave wall with the bird's saliva.<p>The swiftlet feeds aerially on flying ants and other insects.
Conservation
Garnett & Crowley (2000) considered the swiftlet, along with a suite of Christmas Island's other endemics, as critically endangered, with the principal threat coming from the yellow crazy ants which were accidentally introduced to the island. The threat is not only that of direct ant predation of swiftlet nestlings, but also indirectly from potentially massive changes to the ecology of the island caused by the ants. Sometimes the bird breeds in hollow trees and these nests are susceptible to attack by the ants, but the ants do not enter the limestone caverns that are the principle breeding site and are not therefore likely to impact directly on the swiftlet. An application made in 2006 to list the swiftlet as threatened under the Environment Protection and Biodiversity Conservation Act 1999 was unsuccessful.
Photos
Other Birds
American Black Duck
Anas rubripes
A large duck, nearly identical to Mallard in size and shape but with a much darker chocolate-colored body. Bill is yellow with a slight greenish tinge on males, dull grayish-green on females. Note blue wing patch lacks any white borders. Fairly common in northeastern North America, especially along the coast. Large flocks can gather in the winter in saltmarshes and estuaries, but also occurs in smaller numbers on ponds and lakes, often mixed with other duck species. Frequently hybridizes with Mallard. Hybrids usually look darker than typical Mallards and may have an intermediate head pattern; also look for white in the tail or curled feathers above the tail to indicate Mallard genes.
Rufous-vented Tit
Periparus rubidiventris
An active and social small bird of broadleaf and mixed forests, usually in hilly regions. Thin, rather turnip-like crest is often held vertically. Gray with a black head marked by bright white cheek patches. May be confused with Coal Tit, but has a less wispy crest, lacks wingbars, and averages darker and more contrasting overall. Gives high thin calls, often heard as a flock whizzes overhead.
Boat-billed Tody-Tyrant
Hemitriccus josephinae
Tiny, inconspicuous flycatcher with an oversized bill. Plumage generally olive above and yellow below, with faint breast mottling; most readily identified by its large, long bill with entirely pale mandible. A rare resident of tall rainforest, where it seems to prefer areas with many dense vine tangles. Usually encountered alone, sitting deep inside a vine tangle in the mid-story and making short sallies to foliage for insects. Almost always first detected by voice: a series of two or three short hollow notes, somewhat musical and descending in pitch. Unlikely to be confused if seen well, on account of its large bill. Voice is somewhat similar to that of Pelzeln’s Tody-Tyrant but is deeper and seldom exceeds three notes; the two species occupy entirely different habitats.
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