Sunday, April 3, 2011

ID Feature: White-tailed Black-Cockatoos

Although recognised as distinct forms as long ago as 1933 (by none other than ornithologist Ivan Carnaby), Carnaby's (Calyptorhynchus latirostris) and Baudin's (C. baudinii) Black Cockatoos were only officially split by the first Christidis & Boles checklist in 1994 [1]. They are typically described in field guides as 'identical except for bill length', which can be unhelpful for birders who can't get a decent look at the upper mandible. We hope the following information is more useful!

Bill Length (but don't forget width!)
This is the obvious and defining difference between the two species, and reflects a difference in feeding habits. Baudin's use their very long mandible tips to carefully extract seeds from woody fruits (e.g. marri gumnuts), leaving little damage on the nut. Carnaby's tend to much more destructive and will chew the rim off marri nuts to access the seeds.

A male Baudin's Black-Cockatoo carefully hooks the seeds out of a marri nut. Note the brownish tinge to plumage (see General Description below).

Marri nuts after Baudin's Black-Cockatoos have been at work.

By contrast, Carnaby's Black-Cockatoos use their shorter, but broad and powerful mandibles to tear woody fruits apart. Unlike the delicate feeding of Baudin's, Carnaby's must break the rim off marri nuts to extract the seed.

Baudin's bills can be quite strikingly long and thin, hence the rule of thumb "if you only think it's long, it's probably a Carnaby's". However, an examination of multiple specimens in the WA Museum suggests there is variation in the length of the upper mandible tip in both species, and thus a small area of overlap. In fact, the more diagnostic feature of the bill is actually its width - hence Carnaby's gained the specific name latirostris for 'wide-nosed'. Seen from the front, Carnaby's have a broad, arched shape across the top of the bill, whereas Baudin's is more triangular and narrow. The best published illustration of the bills, from Johnstone & Storr [2], is reproduced in WA Bird Notes 89, p. 12 [6] - available online at http://www.birdsaustralia.com.au/the-organisation/wa-bird-notes.html.

Carnaby's (left) and Baudin's (right) specimens on public display in the galleries of the Western Australian Museum. Note that the bill length of both species is variable (possibly due to wear), so that 'long-billed' Carnaby's can approach 'short-billed' Baudin's in bill length.

The difference between bill width in Carnaby's (top) and Baudin's (bottom) is obvious from the front even if the mandible tip is hidden by feathers. Note the arch shape across the top of the Carnaby's bill, but more triangular or diamond shape of the Baudin's mandible.

Call
The standard line that "calls can be distinguished by experienced birders" seems to be written by people who could not, since they usually offer no further information! Visiting east coast birders should find the 'whee-orr' call of Carnaby's very close to that of the Yellow-tailed Black-Cockatoo, with which it has been treated as conspecific in the past.

By comparison, the call of Baudin's is slightly, but noticeably different:
- calls are shorter (0.47s vs. 0.64s for Carnaby's in Saunders' classic study [7]) and sound clipped compared to Carnaby's
- the interval between repeat calls in a series is also shorter than in Carnaby's
- there is less separation of the two 'syllables' of the call (i.e. wheeor, rather than whee-oor; Carnaby's may also stretch their calls to three syllables - i.e. we-EER-oor)
- calls are more shrill and 'shrieky' on the first syllable, whereas Carnaby's tend to sound 'lazier'.

Baudin's also have a more diverse repertoire of contact calls and whistles made while feeding, some of which are unique, partcularly a 'clucking' call. However, as always, take care when ID'ing by call as Baudin's can occasionally make Carnaby's-like calls and vice versa, so it's best to hear a few calls from the bird in question to confirm an ID.

To help illustrate the differences in call, here is a short video (c. 4min) featuring calls from both species.



More comparative audio is available at:
- YouTube (great work by Don Kimball), see also another clip by Don featuring a group Carnaby's
- Graeme Chapman's website (Carnaby's and Baudin's)
- Xeno-Canto

General Description
Scientific texts such as Johnstone & Storr [2] have detailed, but quite literally word-for-word-identical plumage descriptions for the two species. Very few field guides offer any advance on "identical except for bill", but there do appear to be some subtle differences that may be useful, though not diagnostic.
- Simpson & Day [3] pegs Baudin's as "smaller, browner", and many individuals certainly have a noticeable brownish sheen in strong light. Is it possible scientific descriptions have overlooked this feature while studying museum skins under artificial light?

A group of Baudin's Black-Cockatoos. Note the brownish sheen visible in strong sunlight. Is this a helpful ID feature - possibly!

- HANZAB [4] illustrates (but does not confirm in the text) the female Baudin's as having more extensive pale fringing on the breast and belly feathers than female Carnaby's
- Dimensions are subtly different: measurements in Johnstone & Storr [2] show the total length as very similar, but show a slightly longer tail length (and thus by deduction, slightly shorter body length) for Baudin's: 256-295mm (mean 271mm) against 250-275mm (mean 265mm) in Carnaby's. While there's generally at most a centimetre in it, field impressions of a slightly shorter tail in Carnaby's are supported by the measurements. Similarly, Neil Hamilton (ex-curator of birds at Perth Zoo) is quoted as saying Carnaby's is distinct for its "stockier" body, and "longer appearance of the legs" [5].


A female Baudin's Black-Cockatoo. Note the extensive grey fringes on the breast & neck feathers, and relatively long tail. Female Carnaby's are rarely this grey.

Distribution
Whilst both species form quite wide-ranging nomadic flocks in the period after the breeding season (i.e. late summer to winter), Baudin's are generally more predictable in their distribution. Essentially, Baudin's is a forest cockatoo and its heartland is the heavily forested south-west; unlike Carnaby's, it rarely enters the Wheatbelt proper.

In the Perth area, Baudin's only rarely stray onto the coastal plain (except for the eastern most foothills), so the large autumn flocks seen in suburban Perth are almost exclusively Carnaby's. Only south of about Lake Clifton-Waroona are Baudin's likely to occur on the coastal plain. The autumn-winter incursions by Baudin's are instead focussed on the Darling Scarp, north to the vicinity of Mundaring. North of a line from Wanneroo to Toodyay, Carnaby's becomes by far the more likely candidate for black-cockatoo sightings, and this area is in fact one of their traditional strongholds.

The Black-Cockatoo flocks seen around suburban Perth on the coastal plain (mostly in autumn-winter) are almost exclusively Carnaby's.

Feeding Habits
Both species feed regularly on Marri 'honkey nuts' (to use their local name), but Baudin's are far more reliant on them. They also feed on Bull Banksia (Banksia grandis), and pears and apples from orchards. Unfortunately, as a result of this, they are still shot illegally by some orchardists in some areas.

Carnaby's eat a much wider range of seeds and flowers, including heathland Banksia, Hakea, and Grevillea species, and a wider range of eucalypt and sheok fruits. In the metropolitan area, they also feed on introduced species, particularly pines, but also on occasion liquadamber and almond nuts. Indeed, a good rule of thumb is that if it's feeding in a pine, it's almost certainly a Carnaby's, as this is one of their favoured foods on the coastal plain, whereas Baudin's have rarely, if ever, been recorded using them. Further, because of their more varied feeding strategy, Carnaby's are also more likely to be seen feeding in low scrub or on the ground, though Baudin's do sometimes descend to feed on Erodium or dropped nuts.

Carnaby's are often seen feeding in surprisingly small shrubs.


If it's feeding in a pine tree, it's almost certainly a Carnaby's!

Finally, the usual word of caution - land clearing has progressively resulted in greater incursion of Carnaby's into the Jarrah-Marri forests of the south-west. In these areas, mixed flocks sometimes occur, so it pays to check carefully if in doubt.

It would be remiss to end an article on these two species without mentioning their conservation. Both species are threatened in WA due to their low reproduction rates, habitat loss, and in the case case of Baudin's, shooting. Records of their habitat usage can be significant in protecting these species, and we encourage birders in the west to participate in surveys and counts of these species - see the Birds Australia Carnaby's Black-Cockatoo recovery project page for more information about what's being done and how you can get involved. The WA Conservation Council has also launched a web-based petition for black-cockatoo habitat protection.

References
[1] Christidis L. & Boles W. (1994) The Taxonomy and Species of Birds of Australia and its Territories. RAOU, Melbourne.
[2] Johnstone R. & Storr G. (1998) Handbook of Western Australian Birds Volume 1: Non-passerines (Emu to Dollarbird). Western Australian Museum, Perth.
[3] Simpson K. & Day N. (1993) Field Guide to Australian Birds 3rd Edition. Penguin Books, Australia.
[4] eds. Higgins P.J. & Davies S.J.J.F (1999) Handbook of Australian, New Zealand and Antarctic Birds Volume 4: Parrots to Dollarbird. Oxford University Press, Melbourne.
[5] Chapman T. (2000) Cockies in Crisis. Western Australian Bird Notes 95, p. 9.
[6] Burbidge A. & Johnstone R. (1999) Short-billed or Long-billed - which Black-Cockatoo? Western Australian Bird Notes 89, pp. 12-14.
[7] Saunders D.A. (1979) The distribution and taxonomy of White-tailed and Yellow-tailed Black-Cockatoos Calyptorhynchos spp. Emu 79, pp. 215-227.

Further Information
- WA Museum Fact Sheets for Baudin's and Carnaby's
- Some food sources of both species here

3 comments:

  1. So beautiful, I love the call of the Carnaby's cockatoo. Thank you for all this information. I am sending a copy of these calls to my family in England. I live under a cockatoo flyway in Perth.

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  2. We had a flock of White Tailed Black Cockatoo's in our Pepper Gum Tree. They stayed for about 1hr, stripping bark off the tree. We live in Wilson. First time this has happened. Took photo's also Video. We live close to Canning River as well. Tried to count I think there were 9 in total. This happened on Sept 15th 2014.

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  3. Hi, I found your blog randomly. I'm heading to Perth on Sunday from Adelaide, to spend time with a friend - I have never been, so I am super excited to see some new birds! I will be visiting Kaarakin Cockatoo Sanctuary so I will get to see these cockies up close. But this post was very comprehensive; I am hoping to see either, or both (who knows) birds in the wild whilst I am there. Now I have more of an idea what to look and listen out for! Thank you very much. They are beautiful!

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