Subject: Endangering proceeses, fragmented landscapes (fwd)
Date: Jun 23 09:40:21 1994
From: Lawrie Conole - lconole at PIONEER.MOV.VIC.GOV.AU

By day I catalogue and research steam engines, calliopes, computers, mouse
traps, etc.: objects that one typically finds in a science museum. On
weekends and any other spare moments whilst commuting, etc., my thoughts
and energies turn to landscape ecology.

Currently I'm pondering endangering processes in writing up the insular
extinction of 8 species of songbirds (passerines) in the last 20 years in
a relatively large landscape island of 1,050 hectare (circa 2,600 acres)
of woodland surrounded by farmland. I'm interested in examining the
myriad of individual processes in the hope of identifying some key issues;
and perhaps working toward a reversal of some trends. The blanket
statements in island biogeography about the carrying capacity of a given
area in species are not helpful in pinpointing specific endangering
processes. Although I concede that the key issues are difficult, maybe
even impossible, to nail down, I'm optimistic about ameliorating some of
their effects in such a large landscape island. I also acknowledge that
a retrospective examination of endangering processes carries with it some
dangers; what happened then may not be apparent now!

The extinctions are almost all terrestrial and near-terrestrial
insectivores - mirroring the ecologically equivalent small mammals which
became locally extinct 100-150 years before. I can see quite clearly the
changes in vegetation structure and floristics which have a direct impact
on the 8 species and others which are declining too. I also believe a
high density population of exotic _Rattus rattus_ is having an impact on
breeding success (there's a lot written on this topic for oceanic islands,
less for landscape islands). I have an idea that impeded nutrient
cycling, simplifcation of vegetation floristics and structure, plus other
factors, may be resulting in lowered productivity of desirable
invertebrates - particularly indigenous Coleoptera (beetles) and Hemiptera
(bugs) which make up the bulk of the extinct and declining birds' diets.
Some researchers have attempted to address this; but in disturbed
ecosystems the biomass of invertebrates sometimes increases. What is not
currently known is the significance of exotic invertebrates in terms of
their palatability, toxicity, etc. I have no data on this; just a hunch.
As something of a post script, arboreal and volant insectivorous mammals
are doing very well in the same area. It seems that canopy foliage
invertebrate numbers are OK, or perhaps even slightly elevated.

Does anyone out there have comments, psychic insights :-), experience or
references to offer on this can of worms??

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* /\V/\ Lawrie Conole /\V/\ * "And no-one saw the carny go. *
* " Scienceworks " /\V/\ * I say it's funny how things go." *
* 2 Booker Street " * -- Nick Cave *
* Spotswood Victoria 3015 * *
* AUSTRALIA /\V/\ * lconole at pioneer.mov.vic.gov.au *
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