Re Atherton and Large-billed Scrubwrens.
I agree mostly with Keith and Lindsay's comments, but in regard to Mt
Lewis, agree with David. These species cause more debate and confusion
than any two birds in N Qld. It has been suggested that the two species
can be separated by tarsus length but more work needs to be done on
this. To confuse matters further a couple of years ago, someone threw
in the mythical 'yellow-bellied form of the Large-billed Scrubwren'.
I would like to throw in my observations - hopfully not to confuse
everyone even further!
After probably a couple of hundred trips to Mt Lewis and the ranges to
the north (Mt Carbine, Mt Windsor Tablelands etc.) over the last 8 years
and looking at all scrubwrens wherever they appeared, my opinion on the
ratio of Athertons to Large-billed on Mt Lewis is that it is 100:0. I
honestly do not think the Large-billed inhabits the higher altitudes
either on Mt Lewis or in the Mt Carbine/Mt Windsor Tablelands. In fact,
I have never seen anything I could happily call a Large-billed anywhere
along the road leading to Mt Lewis, on the mountain itself - or further
north in these higher altitudes. The birds there are identical to skins
of Atherton in the Qld Museum collected from these northern parts of its
range a few years ago. (Having said that, I would be very interested if
someone does come up with a genuine Large-billed on Mt Lewis). Yet at
Kingfisher Park below Mt Lewis, there is a typical population of
Large-billed. (Athertons are occasionally reported from KP but in 8
years I have never seen a bird which I can say is an Atherton).
To me, a number of features seem to separate the Atherton from the
Large-billed -
1. Plumage - in the Mt Lewis complex and north to Big Tableland just
south of Cooktown, the birds have a distinct yellow wash on the
underparts. The upperparts are quite dark - darker than the upperparts
of the Large-billed upperparts. Bill is important - 'angle' is normal
in Atherton but noticeably slightly up-turned in Large-billed. If one
is looking at a Large-billed, the angle is distinct - the bill appears
'stuck on'.
2. Habits - the Atherton is mostly a solitary bird, the Large-billed
tends to be gregarious. The Atherton mostly inhabits the lower layer,
spending alot of time on the ground. I always think that a solitary
scrubwren on the ground almost has to be an Atherton. The Atherton tends
to be much quieter than the Large-billed and generally inhabits the
lower stratum of the forest -the Large-billed the higher stratum.
However, an Atherton will, on odd occasions, fossick amongst vines to
10-15 metres above ground and the Large-billed will come down close to
the ground.
3. Song - there is a noticeable difference in song - the Atherton's is
very like that of the White-browed while the Large-billed is more
'chattery'. I have never heard a song on Mt Lewis which I can honestly
say is a Large-billed.
4. Nest - there are considerable differences between the two and I
regard this as one of the most important points. The Atherton's nest
is a slightly flattened dome almost identical to that of the
White-browed and always well hidden on the ground. It is usually
slightly smaller than that ot the Large-billed. The Large-billed
invariably builds a bulkier, more rounded, usually fairly obvious nest,
making little effort to conceal it - very similar to that of the
Tropical Scrubwren of Cape York with which it is closely related. I
have found quite a number of Atherton nests on Mt Lewis but never a
Large-billed.
I am beginning to doubt whether the two species co-inhabit, at least in
the northern areas. I have never seen genuine Atherton and Large-billed
in the same local area. Certainly around these northern parts, it seems
to be either one or the other. It is my opinion that some of the
confusion lies with the paler juvenile plumage of the Atherton.
However, that is only part of the intrigue. As Keith and Lindsay say,
there are local plumage differences throughout the range of the
Atherton, especially on the different mountain ranges in the area.
Recently, I spent some time examining scrubwren skins in the Qld
Museum. Fortunately there is quite a series, mostly collected by the
late Julian Ford from various localities throughout the Wet Tropics.
Birds to the north of about Black Mountain (between Kuranda and
Julatten) were identical right through to Big Tableland - with the
noticeable lemon wash across the underparts - fairly easy to pick from
the Large-billed. South of there the lemon wash was less obvious,
making it difficult to pick. And birds from Mt Bellenden Ker had
practically no yellow wash.
This makes a bird in the field on the southern part of the Atherton
Tableland even more difficult to identify. I always wondered why people
there seemed to have more difficulty with these scrubwrens than is the
case on Mt Lewis but no doubt this is the reason.
With so much debate and disagreement between locals, sympathies must go
to visitors wanting to be sure they have seen an Atherton. I would go to
the clearing on Mt Lewis. There are 4 pairs of Atherton's with
territories bordering the clearing (I have found nests of all four). I
would dodge trying to sort them out in the southern areas of the
Tableland!
Anyhow as Keith and Lindsay intimate - we still have alot of work to do.
Lloyd Nielsen.
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