|Western Corellas of the northern race derbyi at New Norcia. Note the long bill, relatively long crest (though not fully extended), and strong red lores not extending over eye.|
Western Corellas (Cacatua pastinator) occur in two distinct populations north and south of the Perth area, each of which have subspecific status. The nominate race pastinator (Muir’s Corella) has a restricted distribution in the south-west, centred around the Lake Muir and Rocky Gully areas, where it is locally common. The more widespread northern subspecies derbyi (synonym butleri) occurs predominantly in the wheatbelt north-east of Perth and can usually be found quite easily in farmland or around country towns such as Moora and Wongan Hills (though Little Corella can also occur so caution is required).
|Western Corellas of the nominate race pastinator near Unicup. Note the tall crest and long upper mandible.|
|Western Corella (race derbyi) at Wongan Hills. Note the long upper mandible, long crest, and obvious red on the lores which does not extend over the eye.|
Little Corellas (C. sanguinea) occur in the greater Perth metropolitan area and are also established around some other large towns further south along the coast (notably Busselton). They also occur in the wheatbelt north and east of Perth, sometimes forming mixed flocks with Western Corellas.
|Little Corella at Jackadder Lake in the Perth suburbs. Note the short upper mandible, relatively restricted red on the lores, and absence of red on the throat.|
Long-billed Corellas (C. tenuirostris) are restricted to the greater Perth area, having established relatively recently from escaped aviary birds, though small populations may also occur around some other larger southern towns like Busselton. Roughly speaking in the Perth area, they extend east into the Darling Scarp, at sites such as Bungendore Park, north of Perth to the Joondalup area, and south to the Mandurah area.
|(Eastern) Long-billed Corella photographed in the Perth area. Note the relatively short crest, long upper mandible, obvious red 'cut-throat' and extensive red on the lores extending over the eye.|
The three features most useful in separating the three corella species are the bill morphology, the size of the crest (only possible if the crest is raised), and the extent of red colouration on the lores and throat. Each of these features is dealt with in turn below. Additionally, information on voice is included as, with experience, this can also be a useful indicator, particularly for identifying Long-billed Corellas.
The bill morphology is a key difference between the three corella species, especially between Little Corella and the two other species. Most noticeably, there is variation in the length of the upper mandible. Little Corella has a noticeably short upper mandible compared to Western and Long-billed Corellas, although observers should be aware that wear can result in some individual variation in upper mandible length within a species, so that ‘long-billed’ Littles may approach ‘short-billed’ Westerns in appearance.
There is little difference in upper mandible length between Western and Long-billed Corella (though Westerns average shorter, especially northern derbyi birds), but fortunately these two species are fairly easily separable based on the extent of red on the lores and throat, and crest length.
|Long-billed Corella at Herdsman Lake. Western Corellas can have similarly long bills, but note the short crest, extensive red 'cut-throat', and extensive red on the lores extending over the eye.|
Long-billed Corellas have relatively short crests compared to Little and Western Corellas. The difference in crest size between Little and Western Corellas is not as noticeable, but Western’s crests are usually slightly longer. Note that these differences are obviously only noticeable when the birds have their crests erect.
There is variation between the three species in the extent of red colouration on the lores and breast. Long-billed Corellas have the most extensive red colouration around the lores and a readily visible, extensive red ‘cut throat’. By contrast, both Little and Western Corellas have less extensive red lores and throat feathers. Both species do have red bases to the throat feathers (slightly more extensive in Western than Little) but these are often not readily visible, particularly in Littles, unless the throat feathers are ruffled (e.g. by wind).
|Comparison photos of the heads of the three corella species, (L-R) Little, Western (derbyi), Western (pastinator), and Long-billed. Note the differing upper mandible lengths and varying amounts of red on the throat and lores.|
|Western Corella (race derbyi) at Wongan Hills. Note the amount of red on the lores is within the range of Little which can also occur at this location - the long upper mandible confirms this bird as a Western.|
The calls of the three species are relatively similar, however there are differences which can be useful particularly in separating Long-billed Corella from the other species. The Long-billed’s call is typically more noticeably disyllabic than that of the Little, which can be useful for identifying distant or unseen birds in the Perth area. The Western Corella’s call resembles that of the Little, so separation between these two species based on call is probably not possible in the field with any confidence. Observers should be aware that caution is needed when attempting to identify birds based on call. In particular, this discussion refers only to the basic contact call of the three species (refer to the audio below - note that the Long-billed recording also contains Little calls in the background) – all three species also make other screeching calls that we consider not reliably distinguishable at this stage. Overall, it is safer to rely on a combination of the morphological features described above where possible.
There are also other recordings for the three species available on the xeno-canto website
Most corellas seen in the south-west can easily be identified by a combination of the features described above, aided by a knowledge of distribution. However, occasional birds turn up that can present more problems, especially around the Perth area where all three species are possible (though Western is rare, as previously stated).
|Western Corella at Herdsman Lake, with Little Corella in the forground. Note particularly the longer upper mandible of the Western, and also the slightly darker, more extensive red lores (though beware overlap in this feature).|
Long-billed Corellas have been observed hybridising with Galahs in the Perth area, so it is possible that Little and Long-billed Corellas also hybridise on occasion (this has been recorded on the east coast). If they occur, Little x Long-billed Corellas could be expected to be relatively similar to Westerns in appearance, as Westerns are intermediate between the other two species in many features (the exception being crest length).
LCB is keen to investigate this further, and we would appreciate any photos of possible Western Corellas, or reports of hybrid breeding pair, from the Perth region if any readers have photos they are prepared to share with us.
|Little (back right) with two Long-billed Corellas, Herdsman Lake. Compare upper mandible length and extent of red on throat and lores of the left-hand Long-bill with the Little.|