Hoy birders,
Thanks for responses to my posting about Bulbuls.
Given responses to my sightings of Bulbuls in the Lake Macquarie area, my
tentative thesis would be that the birds are expanding their range and
consolidating populations, but the dynamics of range transformations are not
well-understood and questions of biodiversity impacts have not been tested.
I've encountered no research whatsoever on the matter of Bulbul impacts on
indigenous birdlife. I have tentative doubts regarding the "harmlessness"
argument: the assumption that they occupy positions in faunal suites without
impacts on indigenous species.
I see issues: the common perception appears to be that Bulbuls have no
significant impacts on indigenous species because their range is limited to
areas where habitat has sustained significant disturbance. My impression is
that Bulbuls appear to be "colonising" riparian zones: in the Lake Macquarie
area they occupy riparian sites in and adjacent to residential areas with
disturbed and fragmented native vegetation. But what is the extent of Bulbul
occupation further inland, following riparian routes, and what might be
potential implications given these routes are significant in the Lake Macquarie
area at least as seasonal migration paths for honeyeaters, to name but one
example of an indigenous species legitimately associated with these routes.
Given riparian zones, for many important reasons, are privileged at the level
of local government administration for conservation management purposes, I'm
sure you can see my concerns! I see the in-principle importance of riparian
conservation management, but what if colonisation by introduced species
displaces indigenous species? Another analogous example: are the same problems
at stake with respect to provision of next-boxes to mitigate the impact of
native vegetation clearance for residential subdivision developments in the
region? In principle, sounds viable, but on the ground there does not appear
to be full consideration - and perhaps due diligence - of short and long term
biodiversity impacts. Brushtailed possums, Rainbow Lorikeets and Common Myna
flourish, other species flounder because the range of hollow sizes and aspects
lost by clearing are not mitigated by 2:1 replacement by nest-boxes, and in any
case there is usually no provision for monitoring and maintenance of
next-boxes. In other words, WINDOW-DRESSING AND LIP SERVICE? Or * ?
As I noted, sightings of Bulbuls are new to me in the Lake Macquarie region: I
observed no Bulbuls between 1978-1986 in the Toronto area, for example, and
sighted my first Bulbul in the region on 14 May 2005. My birding hasn't been
systematic in the period between 1986 and the present, so I remain very curious
as to population dynamics and colonisation patterns of Bulbuls during that time
frame. Their appearance seems a bit swift: have I missed their march from
south to north, from the Sydney metro area to the Central Cost and further
north? Paul Osborne has observed Bulbuls in the Dora Creek area: how long have
they been in the area?
As usual, lots of questions, few answers. Any further thoughts appreciated.
Cheers
Craig Williams
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