Some observations to add to the discussion etc re STSH in Tasmanian and
Antarctic waters..
1. Feeding
Large feeding flocks of STSH occur in Antarctic waters during the summer
months. Flocks of 10 - 40,000 are not uncommon. Flocks will wheel and dive
directly into the water, sometimes from 5 to 10m above the surface. I have
seen flocks of STSH sitting at the surface over large krill swarms at 30m+
depths. When I have been able to time such events, birds were underwater
for periods between 30 to 40 seconds, but this is very approximate.
There are published accounts of STSH diving to 30m+, and also of abalone
divers with STSH with them in the water at 20m+ in Bass St.
A recent study in NZ reported diving depths of 65m in Sooty Shearwaters,
but they are considerably heavier.
2. Proximity to shore
Late in the summer months, STSH assemble in large flocks in the Derwent
River. It is not unusual to see flocks in the 1000s of birds wheeling and
flying close to beaches and shores - I have seen flocks within 100m of
shore.
3. Mortality and beach washed birds
A couple of summers ago, we were getting high numbers of STSH washed up on
beaches in SE Tas. One beach I walked had about 10 STSH/km. At the time, it
was believed to be starvation during the breeding season, rather that at
the onset (ie return from NH) that was responsible for the mortalities.
Hope this helps !
All best
Eric
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