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G'day all
I was actually present at the kite flying
"experiment" which Chris refers to. It was a simple rectangular shape and
it sent thousands of waders up immediately. A shorebird disturbance monitoring
study has been in effect for almost 12 months on the northern side of Roebuck
Bay and this should present some interesting data in this regard when
they're eventually published.
Light aircraft and larger, up to
Boeing 737s, fly across Roebuck Bay not infrequently throughout the day and
my observations are that these seldom cause the tiniest stint to raise its
supercilium. However, helicopters always appear to send the roosting waders into
a panic (with much fist shaking from birders and conservationists
below!).
I too have observed Ospreys taking fish next to
roosting wader flocks without sending them up and yet at other times sending
flocks up immediately. Everyone who has observed large flocks of roosting
birds will report that sometimes they go up as a result of false alarms. It only
takes one nervous bird that thinks that a threat might be present and that's
enough. For those who have ever had to "twinkle" flocks of waders, the subtle
dynamics between a flock which feels secure, or a little wary, or ready to panic
presents and "edge" which can be hard to "work" or define
sometimes.
Habituation and laziness is an
important element which would present a slightly confounding
factor for anyone attempting to research these matters. Many birds have this
well worked out for themselves. I once witnessed an adult White-bellied
Sea-Eagle repeatedly pass over a pretty large mixed flock
(15,000) of godwits, knots, tattlers, terns, etc.. On the first occasion
the flock went up, moved a long way off shore with the whole convoluted "mexican
wave" effect (like a school of fish) in full
wonderful evidence, before returning to their roost. On the second
fly-by, they didn't go so far. On the third, a little less. On the fourth
fly-by, the waders went up only a short way with none of the "mexican wave"
effect. On this occasion, our sea-eagle just stalled in the middle of our lazy
flock, popped out his talons, grasped a nice plump Red-Knot and flew off with
what would have been a rapidly spiflicated victim for his afternoon
snack.
This was a very graphic illustration that our
sea-eagle's theory of habituation was a very good way for him to acquire a feed.
It also proves that even among the birds, it is often brains and
resourcefulness which separates the "haves" from the
"have-knots".
And, by the way, Noisy Miners will prepare a
mobbing offence against just about any creature that invades their turf -
whether it's forward or in reverse, frequent or rare.
Happy Birding
Ricki
Belrose, Sydney
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