Yes the graph looks real enough and the
numbers look right. However, once again it becomes necessary to mention that a
graph such as that has two components included. Number of observer weeks surveyed
and presence of the birds. So it is necessary to consider the trends of observer
weeks surveyed over the year (Figure 6 of the GBS Report) which accounts for a
lot of the observed variation which might be purported to be just changes in bird
numbers but it certainly is not. The trend as shown by month in the GBS Report graph
(and in the text, which describes the unique bimodal pattern) and taking into
account observer weeks, shows the data in a smoother style and greatly reduces the
obvious observer activity bias. Also note again that Martin’s graph splits
the GBS year into two halves and recombines them (as Jan to Dec), which is not representing
it in the way the data are collected or in the way all prior published
representations of GBS data (in ABR, BOCG and the GBS Report), over the years have
shown them.
Philip Veerman
24 Castley Circuit
Kambah ACT
2902
02 - 62314041
-----Original Message-----
From: martin
butterfield []
Sent: Sunday, 29 March 2009 8:54 PM
To: billrobertson
Cc:
Subject: Re: [canberrabirds]
Rufous Fantail in Giralang
There have been 218 Rufous Fantails (as opposed to
22,861 Grey Fantails) reported on GBS Charts over the past 27 years. So, if I
was Mr M. Python, I would perhaps go a little stronger than "something a
little different", although not perhaps as far as "something
completely different".
A Chart of when the Rufous Fantails have been reported in terms of GBS week is
attached clearly showing the bimodal nature of these observations as birds pass
through on their way to and from the soggier gullies in the mountains. We
are now in GBS week 13 coinciding with the left-hand peak of the distribution.
Martin
On Sun, Mar 29, 2009 at
6:38 PM, billrobertson <>
wrote:
Our garden in (dry)
Giralang occasionally produces something a little
different in the bird line. This late afternoon it was a Rufous Fantail (a
first for our garden bird chart) together with our usual mixed feeding flock
of Weebill, Superb Fairywren and Silvereye.
Earlier this afternoon out at Uriarra Crossing we saw small flocks of
migrating honeyeaters, and also Dusky Woodswallow and Red-browed Finch.
Large numbers of Sulphur-crested Cockatoos were quietly shredding the
casuarinas. A White-throated Treecreeper gleaned insects as we sat watching
nearby.
Margaret Robertson
