I was a member of a University of WA research team which conducted a
three-year study of Spinifexbirds on Barrow Island, WA in the early 1990s.
Spinifexbirds can be notoriously difficult to find, especially in areas of
dense spinifex cover. We attached radio-transmitters to Spinifexbirds during
this study and, quite frankly, on many occasions we would not have known
that the birds were present in an area without receiving the signals from
the transmitters.
Spinifexbirds can be flushed from spinifex clumps by lines of people walking
through the spinifex habitat. But if a Spinifexbird decides to hide in a
large spinifex clump, it is quite easy to walk past it without detecting the
bird. So I'm not surprised to hear of extensions to known ranges of this
species because if present in very low numbers in these areas they would be
extremely difficult to detect.
For those interested in learning more about our Spinifexbird research, the
title and abstract of our paper is presented below.
Stephen Ambrose
Ryde, NSW
Ambrose, S.J., S.D. Bradshaw, P.C. Withers and D.P. Murphy (1996). Water and
Energy Balance of Captive and Free-Ranging Spinifexbirds (Eremiornis
carteri) North (Aves:Sylviidae) on Barrow Island, Western Australia.
Australian Journal of Zoology 44(2):107-117
Abstract
The mean annual rainfall of Barrow Island, located about 90 km north of
Onslow off the arid Western Australian coast, is 324 mm, 74% of which falls
as cyclonic rain between February and May. Spinifexbirds captured in May
1992 had a mean body mass of 12.3 +/- 0.3 g and a total body water content
(TBW) of 774 +/- 1.6%. In December 1992 the mean body mass was significantly
lower (11.7 +/- 0.2 g; P < 0.05), despite a TBW of 73.4 +/- 1.0%.
Spinifexbirds maintained water balance in both seasons, but water flux rates
were significantly higher in May (P = 0.01). Respective influx and efflux
rates in May were 0.70 +/- 0.30 and 0.72 +/- 0.03 mL (g day)(-1) compared
with 0.60 +/- 0.04 and 0.57 +/- 0.04 mL (g day)(-1) in December. Field
metabolic rates (FMRs), measured with doubly-labelled water ((3)HH(18)0),
did not differ significantly between the two periods. The mean FMR in May
was 6.8 +/- 0.6 mL CO2 (g h)(-1) compared with 7.2 +/- 0.9 mL CO2 (g h)(-1)
in December, similar to rates predicted by Nagy and Peterson (1988) for a
similar-sized passerine. The thermoneutral zone (TNZ) of spinifexbirds,
determined by metabolic laboratory trials in December, extended from 30 to
39 degrees C. The standard metabolic rate (SMR) within the TNZ was 2.9 +/-
0.1 mL O-2 (g h)(-1), which is up to 20% lower than predicted values. Body
temperature was maintained at 39.1 degrees C in the TNZ, but birds became
hyperthermic at ambient temperatures (T(a)s) higher than 35 degrees C, with
body temperatures reaching 44 degrees C. Wet thermal conductance and
evaporative water loss increased markedly at T(a)s > 35 degrees C. The data
suggest that spinifexbirds have limited physiological adaptations to desert
conditions compared with some other arid-zone birds.
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