Thanks to Michael Atzeni for bringing this question up again. But although
Hugo Phillips and Ian Gynther have advanced the discussion admirably, I
still don't think we've got a good rule of thumb yet for this convention we
are seeking - and which we need if we are to develop a uniform approach to
this.
If a given population of birds appears to be successful in a new
environment, I don't think we need to concern ourselves overmuch with how
that population got there, or if we like the birds being there or not,
but should just accept that they are there and seek to determine if that
population should be considered transient or established. It's only for
one-offs, or small parties not evidently breeding, that we need to worry
about where they came from.
I agree with Ian & Hugo about requiring successful breeding of a
self-sustaining population. The Introductory Section of Volume 1 of the
Handbook refers on page 15 under Treatment and Presentation to a "viable
feral population"
But, what does viable mean? If it means Mute Swans clinging on by the skin
of their teeth at Lake Leake in Tasmania, or Wild Turkeys and Peafowl
existing here and there in small communities, it could equally well mean
increasing numbers of Long-billed Corellas thriving in populations all over
SE Queensland - maybe threatening to join up and take over from many of the
local parrots - we don't have to like it, or want it, or encourage it, but
we do have to record it.
So, given that there are plenty of species on the Australian list that were
either deliberately introduced or which derive from escaped individuals, if
we choose to keep our subset political lists - Queensland, Victoria, this
valley, my garden, (I once had a list for a special tree) etc., surely we
should seek to apply the same criteria as have been applied for inclusion of
those categories of species on the Australian list.
I spoke to both Walter Boles and Les Christidis about this earlier today.
What criteria had been applied to inclusion of these sorts of birds for the
1994 Checklist - were there set criteria, cut-off points etc? Their response
in essence was to the effect that a population had to be seen to be
recruiting, not declining.
Les kindly referred me to a paper published in British Birds (vol 91, nos
1&2, January/February 1998) discussing a revised categorisation of the
British List.
Categories A & B describe species that occurred in an apparently natural
state since, and before 1 Jan 1950 respectively. Category C "has been
subdivided to make clear the origins of those species that are established
in the wild as a result of introductions, either deliberate or accidental.
Previously the word 'feral' was often applied to all such species, whether
they were naturalised aliens ........ or re-established as part of a
conservation programme."
Category D is a holding category mostly for one-offs of dubious origin. The
example is given of a bird found dead on the tideline. If there is any doubt
about its origin it goes in Category D; If there is no doubt
it belongs in Category A providing it arrived naturally, or Category E if it
escaped from captivity.
Category E is for species occurring as escapes, but which are not yet
firmly established. However, escapes which have bred are in Category E*.
I thought we were getting somewhere for a while, but now I see that an
escaped breeder is in Category E*, while its offspring when they breed
perhaps qualify for Category C. Be that as it may, Les Christidis tells me
that he is now working on developing divisions and categories for the
Australian List along these and similar lines followed by the American
Birding Association.
In the interim, I suggest that inclusion of a feral(?) population on a list
should be a function not of origin or desirability, but simply of whether
the population is growing, not declining, while living free of direct human
intervention.
Once a species has been added it could well at a later time decline out of
sight, which can equally well occur to non-feral, wholly wild populations.
Bill Jolly
"Abberton", Helidon, Qld
ph 07 46976111
fax 07 46976056
email:
Visit our website at: www.abberton.org
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