Ian May makes a valid - but dangerous point - about environmental weeds, such
as blackberry. Removing these can leave superb fairywrens (SFWs) without
suitable nesting sites. There was a case in Springvale where blackberry
removal was followed by the species vanishing.
In contrast at the new Kararook Park blackberries were removed by Parks
Victoria from the derelict land but the SFWs are thriving. Why? Because around
the same time native vegetation was restored. We should always try to think
about REPLACING not just REMOVING weeds.
The alternative is allowing environmental weeds to take over. Blackberries,
and our foreshore equivalent boxthorn, are readily spread by blackbirds, foxes
etc. etc. and will swamp native plants (and biodiversity).
Over the last 6 summers we have found 14 SFW nests in the foreshore of which
two were in one boxthorn plant used twice, and one in dead boxthorn (left as
cover while regeneration takes place). But 6 were in recently revegetated sites
(in Grey Saltbush and Cushion Bush) and 3 in grasses with the other 2 in Hedge
Wattles (probably planted). The proportion of sites in different sorts of
vegetation is quite similar to that in BA nest site records for the Melbourne
area although it does not include bracken and sword sedges.
As to the sites I mentioned, where the arrival of Butcherbirds coincided with
the disappearance of SFWs, neither has had any substantial removal of
blackberry or boxthorn (or any changes in vegetation). Rather the Butcherbirds
are there now operating in vegetation which is much more dense than the areas
they seem to prefer.
Of course there are other possibilities. At those sites we have been worried
about "meso-predator" release (cat trapping could result in more black rats)
and foxes going for wrens following rabbit eradication. But the evidence points
more strongly to the Butcherbirds.
Michael Norris
Bayside Friends of Native Wildlife
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