I guess this raises the issue as well Paul of how important it is to record
(if you are going to record!) all species seen - I have come across people
who refuse to record sightings of "ferals" - but without such recording how
do we document their spread and (hopefully!) decline. Equally some of the
reports I see in some of the online databases indicate that people tend to
report the rare birds but not the common ones (even if not feral) - for
example last time I checked one of the databases showed that Black Swan was
recorded on 60% of all visits to the Western Treatment Plant, Werribee - yet
it would be a rare visit there when a swan was not seen I suspect!
On 07/05/2008, Paul Dodd <> wrote:
>
> You've made an interesting observation here, Jen. I suspect that with
> rarities such as the OBP or the Mallee Emu-wren, there are enough people
> looking for them at any given time that we would notice pretty well
> immediately if they "disappeared". That's probably true for a number of
> other slightly less rare species. But for a species such as the Bulbul where
> people may occasionally look for it, it could be many years before we
> realised that a particular population was extinct.
>
> Which brings up another issue - when is a population deemed to be extinct?
> If there are no sightings for ten years? (The opposite of the ten-year
> self-sustaining population "rule") Longer, maybe? Presumably if the mean
> life-expectancy of members of a species is greater than ten years, then we'd
> want to use a figure of much more than this.
>
> Apologies for reducing such a potentially emotive issue to mere statistics.
>
> Paul Dodd
> Docklands, Melbourne
>
>
>
>
> -----Original Message-----
> From: [mailto:
> On Behalf Of
> Sent: Wednesday, 7 May 2008 1:50 PM
> To:
> Subject: [Birding-Aus] Local extinction?
>
> Hi all,
>
> The discussion on ferals has got me thinking. One of the first birds on my
> life list was the Red-whiskered Bulbul. When growing up near the Yarra they
> were never common but could always be found in our street.
>
> In recent years the only location I had for them was the boulevard in
> Ivanhoe, and even then there were only one or two. From about 2000 we would
> go over at least once a year to get them on the year list. In 2007 we could
> not find any, nor again in 2008. It seems that the last of these "ferals" in
> Melbourne has fallen off its perch – or had that perch chopped from beneath
> it?
>
> The loss is certainly not a threat to the world population, and some may
> applaud this loss, BUT; it has made me realize how easily a bird can become
> locally extinct without anyone particularly realizing it. It also shows, to
> me anyway, how important the B-A and DSE atlas's are and how important
> records are. For example I have reported two mammal sightings to DSE this
> year, mainly to find out what I had seen, and in both cases the sighting was
> from a location not recorded before for the species. If we do not know were
> our birds and mammals are we may not notice when their range changes.
>
> Back to the Bulbuls, perhaps future field guides will now need to delete
> them from the Melbourne area?
>
> As an aside we are off this weekend to see the reported flocks of Flock
> Bronzewing. The sight of 1000s of these birds in a flock seems somewhat
> iconic to the outback and is something I have wanted to see since I first
> started bird watching. I also relate it to the historic reports of the
> American Passenger Pigeon. I do hope our Bronzewings never suffer the same
> fate.
>
> Happy birding everyone
>
> Jen
>
>
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