Jack,
The bird guide you spoke to at Lamington NPabout Ground Thrush couldn't
have got it more wrong. The Russet-tailed is far more common and
widespread than the Bassian in Lamington. I visitied Lamington
regularly for many years through the 1970s and 1980s and worked as a
guide for O'Reilly's for 3 years until 1991 and these two species were
of specieal interest over that time.
The Bassian inhabited the higher altitudes down to about 850 metres -
there seemed to be a casual drift down to about that level during
winter, vacating the highest areas and a drift back to higher altitudes
in spring and summer where they bred. We always regarded the guest
house area (O'Reilly's) as the general lower altitudinal limit of the
Bassian. We would see the Russet-tailed a kilometre or so out from the
guest house on the border track before they petered out. (I have heard
that the Bassian has become more common around the guest house in recent
years). Binna Burra is lower in altitude than O'Reillys (650 metres as
against 920 metres).
The Russet-tailed was the most interesting. It inhabited the lower
areas, up to about 1,000 metres. It vacated the rainforest almost
completely from about late April until September. Numbers built up over
a few weeks in April before leaving and again in September when they
returned to a point where they were quite prolific in the more open
areas e.g. along roads. By May, they had gone with the exception of a
very odd bird and by October, numbers had settled down to normal
breeding numbers. It always puzzled me as to where they went in the
winter time - certainly not into lower level rainforests. Driving up
the road to O'Reillys very early morning when they moved back in April,
one one would flush dozens from the road sides.
When one saw the two species more or less each day, the more subtle
differences became obvious. The Russet-tailed is a slightly more
slender, finer bird that the Bassian which is more plumpish. The russet
on the rump of the Russet-tailed is not always obvious unless one gets
good light on it. Russet-tailed is distinctly shorter tailed.
The main difference though was in the white in the tail which was the
best field mark if you could get a look at it. Only the corners of the
Bassian tail is white while the Russet-tailed has white sides for the
greater length. If a bird flushed ahead of you, you could often see the
extent of the white in the tail. However, they always had to spread the
tail on alighting before one could get that ID - sometimes they landed
without spreading the tail. I am aware that a few people claim that
skins have been collected intermediate between the two (as far as white
in the tail is concerned). During the time I spent at Lamington over 20
years and with thousands of Ground Thrush sightings, I never saw
anything like that - it was distinctly either one species or the other.
I participated in many of O'Reilly's Bird Weeks as well and no one
reported anything other than that.
Call is diagnostic too - they call first thing of a morning and last
thing just before dark, rarely (probably never) through the day - the
"pee-poo" of the Russet-tailed and the Blackbird type warbling of the
Bassian.
Hope this helps to ID your Ground Thrush - my bet is that they would
have been Russet-tailed at that altitude - I never saw Bassian even
close to Binna Burra and presumably their habits have not changed too
much over the past 10 years.
An item of interest - During an extreme drought in 1991 when many
rainforest trees died, we picked up quite a few birds dead along the
walking tracks. Nearly all were the two thrush species. This was
probably because their diet was principally worms and the drought had
driven the worms deep underground. In one instance near the guest house
at the height of the drought, an old leg of mutton somehow was lodged
into a tree fork a couple of metres above the ground, just inside the
rainforest (someone had thrown it there) . It became fly blown and the
maggots dropped to the ground over a few days. A Russet-tailed GT found
them and spent all of its time digging at the ground for the maggots
with its bill as though they were worms, unaware they were dropping from
above. Over about 6-7 days, it dug a hole in the ground by flicking out
the soil with its bill about 7 cm deep and about 50 cm wide in its
search for the maggots (I watched it every day). I tried to feed the
thrush various items including grated cheese thrown into the hole it had
dug to keep it alive but it was not interested, ignoring it all, being
hell bent on "digging" up the maggots. After about 7 days, I found it
dead in the middle of the hole it had dug.
Lloyd Nielsen
Mt Molloy Nth Qld.
>
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
To unsubscribe from this mailing list, send the message
"unsubscribe birding-aus" (no quotes, no Subject line)
to
|
