I have been following the Short-tailed Shearwater story with interest. I
love these birds! I certainly bear them no ill-will.
But lets face it - if millions didn't die each year, the planet would
soon become covered in them. In reality, that's not going to happen,
because all sorts of things tend to keep populations in check, unless
you are like humans, and clever enough to avoid population stability.
Every year, millions of STSWs migrate down the east coast of Australia,
with the first year birds coming through about now. Every year, huge
numbers of them die during this time and end up on beaches, alarming
people who don't understand biology. Some years we see more dead than
other years, and some years we see huge wrecks. But what does a wreck mean?
There are all sorts of things a wreck could mean. I'll suggest a few.
1) Recent breeding seasons have been unusually productive
2) They had an extra good time in their wintering range, so there are
more than usual still alive now
3) Conditions have resulted in more of them flying where we can see
them, so we see more dying
4) They are experiencing very tough conditions and there will be far
fewer breeding next season as a result.
Of these, only the last is anything to worry about. How do you
distinguish between these (and other) possibilities? You need trained
biologists who understand population dynamics and the specifics of how
they relate to STSWs, and you need them to have access to data
collected for meaningful monitoring of the species.
Witnessing a wreck is a fascinating, and maybe scary thing, but
understanding what it means requires actual science, not knee-jerk
reactions.
With regard to what Greg and others have noted recently, if there are
unusually large numbers present in the near off-shore waters, then you
would expect to see unusually large numbers dying. Still doesn't give
any indication of whether or not the mortality is abnormal, or of any
consequence to the species.
Cheers, Chris.
On 11/02/2013 03:37 AM, Greg Roberts wrote:
Short-tailed Shearwaters were in unusually large numbers.
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