Sunshine Coast Birds

Birding and other wildlife experiences from the Sunshine Coast and elsewhere in Australia - and from overseas - with scribblings about travel, environmental issues, kayaking, hiking and camping.

Wednesday, 30 August 2017

Russet-tailed Thrush & Bassian Thrush in South-East Queensland

Russet-tailed Thrush
The difficulty of distinguishing Bassian Thrush from Russet-tailed Thrush in the field has led to a good deal of confusion about the respective distributional ranges of these two very similar species, especially in areas where they potentially overlap. Both occur in South-East Queensland, where considerable debate has taken place about which species occurs where.  
The evidence suggests that Bassian Thrush in South-East Queensland is primarily a bird of the higher altitudes (primarily in rainforest) of the Main Range and adjoining Great Dividing Range. The species is resident across these ranges from Lamington and Springbrook national parks in the south to the Bunya Mountains in the north. Russet-tailed Thrush occurs generally at lower altitudes; it is widespread and much more common than Bassian in the region. The two species occur together in a relatively narrow altitudinal band in a small number of sites including O'Reilly's Guest House in Lamington National Park and the Goomburra section of Main Range National Park.
Bassian Thrush
The difficulty of identifying the two species can not be under-estimated. I am among many who have at times made the wrong call, corrected only when photographs were scrutinised later. Some oft-mentioned features are of little benefit with identification in the field. For instance, Russet-tailed has a little more white in the outer tail feathers but this is very difficult to discern; the apparent absence of white in the tail of a bird is essentially meaningless. Russet-tailed has a more rusty hue to the lower upperparts (evident in the first image on this post) with Bassian having a somewhat more olive wash. This feature however is unreliable as it is difficult to nail down, especially with the bird so often being in poor light.

The best identification features seem to be the more obvious buff tips to the wing coverts of Russet-tailed Thrush, and the relatively narrow, longer bill of Russet-tailed. However, even these features are fraught, especially as juvenile Bassian Thrush can show some buff edging to the wing coverts. Call is therefore of critical importance to identifying these two thrushes; the calls are highly distinctive and are given frequently.

In the absence of definitive photographs, specimens or call recordings, I had come to the conclusion that Bassian Thrush is absent from those South-East Queensland mountain ranges which are generally lower than the Main Range and Great Dividing Range. I and others, for instance, have searched long and hard for Bassian Thrush without success in the Conondale and Blackall ranges in the Sunshine Coast hinterland

Russet-tailed Thrush
I have camped often in plenty of sites at all altitudes in this area over the past 40 years and have heard and seen only Russet-tailed.

Chris Corben, a highly regarded observer, was employed for several years by the then state Forestry Department to undertake wildlife research in the Conondale Range in the 1980s. Chris, one of the first birders to detect differences between the two taxa, was constantly on the lookout for Bassian Thrush - his base high in the mountains was amid ideal habitat - but he also failed to encounter a single bird.

However, it has emerged that Bassian Thrush is a rare visitor at least to the D'Aguilar Range north of Brisbane. Judith Hoyle lives in the rainforest atop Mt Glorious, where the altitude is similar to that of some sites where Bassian Thrush occurs regularly further afield. Judith has heard Bassian Thrush on two occasions at Mt Glorious. One bird was present for a week in April 2014 in the forest next to her home, its presence revealed by regular calling in the mornings and early evenings. A second bird was heard calling in March 2016 and on this occasion, Judith managed to record it. That call, which Judith was kind enough to send to me, is unmistakably that of a Bassian Thrush.

Bassian Thrush
Judith noted that both Bassian Thrushes were exceptionally shy compared to the Russet-taileds which are common residents about her home. It seems that Bassian Thrush is a rare autumn visitor to the mountain. Bassian Thrush and Russet-tailed Thrush both undergo a degree of altitudinal migration, with some birds moving to lower elevations with the onset of cooler weather. It seems likely that the occasional bird from the Main Range-Great Dividing Range population wanders to other areas.



1 comment:

  1. Very interesting Greg. Sometimes we see Thrush at Bulburin, subtropical rainforest around 600m elevation north of Bundaberg. I've never been confident enough to decide what species, and will make sure I get some sound recordings next time.

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