g'Day Bob and others
Several days before 22 January 1974, when the spectacular outback floods
of 1974 commenced bringing more than 1125 mm of rain (45 inches in 3
months) to much of the Lake Eyre Basin between January and April,
Whiskered Terns were seen feeding over gibber plains west of Lake
Callabonna SA. Before the rain, there were no areas of surface water
for many miles and I have often wondered from where did they come?.
Again in 1989, several days before heavy rains broke across the northern
Flinders ranges, out from Beltana, Whiskered Terns were hawking over
Mitchell grass plains near Lake Torrens. Local weather was hot and
humid, typical monsoonal build up that characterizes outback weather
before a major summer storm breaks (an upper level low?). Perhaps the
humidity or the overcast conditions with a falling barometer stirs up
many insects before the rain.
It had been dry for some time around Leigh Creek prior to heavy rains
(250 mm in 24 hours) which filled Lake Torrens on 14 March 1989.
Several days before this flood started, large numbers of Cockateil and
also Gull-billed Terns also suddenly appeared. Both species had been
absent from the area for some time before this. Are some of these birds
perhaps a barometer to rain coming?
The occurrence of Whiskered Terns away from water in these outback areas
is not always associated with summer storms. In early September 2001
(last year) we observed a flock of more than 50 with about 20 Gull
billed Terns flying across the gibber plains on Murnpeowie Station at
the junction of the Strzelecki track and Mt Hopeless road turn off. On
this occasion it was late afternoon, the weather was windy and cold and
the terns seemed to be travelling south low over the plains. However
not far to the east along Moppacollina channel that joins Lake
Callabonna to Lake Blanche, there were some flooded lakes from recent
local rains so they might have been travelling between local sites.
What do you think the occurrence of the terns over dry country is
telling us Bob? Could there be a big summer rain coming?
Regards
Ian May
Birding-Aus is on the Web at
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