Notes
on Trillers in Vanuatu
May 2009
By Stephen Totterman
Vanuatu
has two Triller species: Long-tailed Triller Lalage
leucopyga and Polynesian Triller Lalage maculosa.
These birds are often confused by inexperienced observers.
The main reason is that some races of Long-tailed Trillers
in Vanuatu have a white lores and supercilium like Polynesian
Trillers and this is not illustrated in the field guide Birds of
The Solomons, Vanuatu and New Caledonia
(Doughty et al, 1999). As well,
the field guide states that both species are common throughout
Vanuatu, which is not the case; Long-tailed Trillers are
more widespread and common than Polynesian Trillers.
Table
1 presents some differences that may helpful in identifying
trillers in Vanuatu. Three subspecies of Long-tailed Triller
have been described in Vanuatu (Mayr
and Ripley, 1941) and this variability is main source
of confusion.
| |
Long-tailed
Triller
Lalage leucopyga |
Polynesian
Triller
Lalage maculosa |
| Distribution |
All
islands (Map: Figure 1) |
Central
islands (Map: Figure 1) |
| Subspecies |
L.
l. simillima: Erromango, Tanna, Aneityum (southern
islands).
L. l. albiloris: Santo to Efate
(central islands).
L. l. deficiens: Banks and Torres (northern
islands). |
L.
m. ultima: Efate, Nguna, Emao.
L. m. modesta: Santo to Emae. |
| Size |
Slightly
larger (17-18 cm). |
Appears
more plump (15-16 cm). |
| Tail/Wing |
Relatively long tail. |
|
| Upperparts |
Adult
male: Glossy black.
Female
and immature: Brownish black. |
Adult
male: Dull black.
Female and immature: Rather pale, brownish black. |
| White
barring of upperparts |
Adult:
None.
Immature:
Pronounced barring (scaly appearance).
|
Adult: Finely barred white. More
pronounced on L. m. ultima.
Immature: Pronounced barring (scaly appearance).
|
| Wing
feathers |
Adult: Black.
Immature: Whiteish edges. |
Edged
white. |
| Underparts |
Pure
white or buffy white. |
L. m. ultima: Almost pure white.
L.
m. modesta: Greyish-white, sometimes a distinct buffy wash. |
| Black barring
of underparts |
None. |
L.
m. ultima: Almost none.
L. m. modesta: Sides of neck
and breast. |
| Crown |
Black. |
White
streaks, more pronounced on
L. m. ultima. |
| Lores |
L.
l. simillima: Black.
L. l. albiloris: White.
L. l. deficiens: Little or no white. |
White. |
| White
supercilium |
L.
l. simillima: None.
L. l. albiloris: Many individuals from Efate
have a pronounced supercilium. Birds from other
islands have the supercilium less developed or absent.
L. l. deficiens: None. |
Broad,
continues to nape. |
| Lower
mandible |
Black. |
Yellowish-Brown. |
Table
1. Long-tailed and Polynesian Trillers compared.
Based on Mayr and Ripley (1941)
with some information from Bregulla
(1992).
Figure 1. Distribution map of Long-tailed Triller in Vanuatu (left) versus Polynesian Triller (right).
Dark tones illustrate distribution in Mayr and Ripley (1941).
Lighter tones show additional distribution information in Bregulla (1992).
Dotted lines show inferred boundaries of distribution.
Figure
2 illustrates a spectrum of variation in the trillers
of Vanuatu. Birds that are well separated
on this diagram should be distinguishable in the field.
Figure
2. A spectrum of variation, from Long-tailed to
Polynesian Triller.
On Efate, the ranges of L. l. albiloris and
L. m. ultima overlap and Long-tailed Trillers may be mistaken for Polynesian Trillers. Many
individuals of L. l. albiloris from Efate have
a pronounced supercilium stripe, like Polynesian Trillers. To identify Long-tailed Trillers
on Efate, look for glossy black upperparts, a relatively
long tail and listen to their calls. Long-tailed Trillers
are quite vocal, with frequent rasping call notes and a loud,
polysyllabic song 'tee-zeeia, tee-zeeia, tee-zeeia'.
Abundance and habitat
use is different for the two trillers in Vanuatu.
The Long-tailed Triller is more common. It seems to prefer open country and is common in
plantations, gardens and secondary growth. VanBirds has few recent records of Polynesian Trillers. They
are found mainly in forests and along the forest edge.
The
Whitney South Sea Expedition collected birds in Vanuatu
in the 1920s and Mayr and Ripley
published their findings and analysis of the genus Lalage in
1941. This is probably the only study of trillers
in the Pacific islands.
In Vanuatu, there is more variation than described in Table 1. There is a need for more fieldwork
and a fresh review of the genus Lalage in the region.
Vanuatu is unusual in that the range of Long-tailed Trillers and Polynesian Trillers
overlap in the central islands. Most Pacific islands only
have one species of triller.
With
our current knowledge of the trillers in Vanuatu,
bird watchers should take care in identifying Polynesian
Trillers.
In May 2009, VanBirds has images and recordings only for Long-tailed Trillers.
|
