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Very
true. Before it happens I will mention, there is a cautionary note towards
looking at GBS data for ideas on this. One relevant feature of the question is
that the GBS calendar splits winters between years. That is why the question is
easier addressed at least on GBS data for "summer migrants" than "winter
migrants". Of course the COG ABR has always been on a July to June year also.
This
is why on The GBS Report I did graphs of a different style (calendar year rather
than financial year) for the winter migrants. (This is explained in detail on
pages 29 & 30.) You will note that this system was used in Birds of Canberra
Gardens edition 1 (because I supplied those graphs and the reason was given on
page ix). In Birds of Canberra Gardens edition 2 there does not appear to
be any such thought given to this issue. As far as I see it is not mentioned at
all (at least as to why the two versions should differ) and all the graphs
are labelled as calendar year, even though none of the data were
collected or analysed as calendar year. Apart from that the squiggle
obscures inter year variations anyway and I find it impossible to know what the
data are. Page viii says that the graphs for the Silvereye and Grey Fantail look
similar but I think whoever wrote that forgot to put on their glasses. If they
wrote that the graphs for the Silvereye and Weebill (p 32) look similar,
well then that would be sensible...........
Philip
Yes,
I think that’s a good example of variability. The DWS is a variable
migrant.
If
I remember last Winter, I might say “Oh there’s lots of DWSs around all
year”. Perhaps that was also true for 2007. Someone who bases their
understanding on only a low year or two might say “It’s very unusual to see a
DWS in Winter”.
BF
Cuckoo-shrike is also highly variable. Query pardalotes, orioles, YFHE
etc.
What
this means is comments on seasonal occurrence should have inserted “In some
years … but in other years …”.
It
brings us no closer to understanding typical/non-typical (if meaningful at all),
or the nature of the trend, or the cycle, whichever it is.
From: Roger Curnow [
Sent: Tuesday,
28 June 2011 8:28 PM
To: Cog Chatline
Subject: Re:
[canberrabirds] winterbirds 2011
Out in H11
i haven’t seen one Dusky woodswallow since June
1.
Last year I
could find 37 (? haven’t checked my records) most
days.
Sent: Tuesday, June 28,
2011 4:16 PM
Subject: RE: [canberrabirds]
winterbirds 2011
Yes
Tony – the summary of last year’s exercise is in the list archive for 3 August
2010. There were 5 reports of reed-warblers for those 8 weeks, single
birds at various locations.
My
impression is that there are less of the targeted species around this
year. Whatever the actual temp readings, I think this Winter has a harder
edge to it.
From: Tony Willis [
Sent: Tuesday,
28 June 2011 3:45 PM
To: canberrabirds chatline; Ian Anderson;
David.Clark
Subject: [canberrabirds] winterbirds
2011
Last year Geoffrey Dabb conducted
an interesting survey on birds that overwinter in Canberra but belong to species
that are generally accepted as being migrants, that leave us in autumn and
return the following spring.
Last Saturday, 25th June, a group of
us did a circumnavigation of Lake Ginniderra, and in the vicinity of the boat
ramp at MacDermott Place we observed this Australian reed-warbler. It was
originally in the reeds but ascended a casuarina as we watched, apparently
searching for food. As far as I remember, it was silent the whole
time.
I think it has been proposed previously that some A. reed-warblers
might stay through winter but are generally overlooked as they are not calling
through this period. We reported an A. reed-warbler last year in the same
location, on the 31st July.
Tony
Willis
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