Well this is definitely lots to chew on for sure. At this point I am still
under the impression that parrots are more easily seen in april/may as
opposed to Aug/sept. Hope I have this correct. Anyone else want to chime
in and offer their perspective.
Don
On Wed, Dec 20, 2017 at 3:35 PM, Philip Veerman <>
wrote:
> The information that Martin refers to, is available in my book: "Canberra
> Birds: A Report on the first 21 years of the Garden Bird Survey". This is a
> detailed 130 page analysis of the GBS, that has been run by Canberra
> Ornithologists Group (COG) in Canberra, continuously since July 1981.
> Martin
> has referred to 30 years, which I can suggest is easily done by noting that
> the next 9 (+) years have presumably continued the same trend as was
> therein
> documented for the first 21 years, for those two and indeed many other
> species. There is however no compiled analysis since the first 21 years.
> What Martin wrote is correct. But it is unrealistic to describe the other
> factors in play, in an email in isolation. The book, indeed the GBS
> analysis, from its inception (1981), has gone to great lengths to adjust
> for
> observer effort. As Martin has also had a long involvement with the GBS and
> is well aware of the analysis (especially during those 9 + years) and has
> my
> book, I am intrigued with his stated surprise that "adjusting for observer
> effort doesn't affect the pattern of numbers recorded greatly". Also the
> months mentioned should not be taken in isolation but as a continuum
> through
> the year. When seen as a graph the sequence is seen as smooth as part of a
> regular cycle. Among the 221 species recorded in the first 21 years (now
> several more added since) there were more than 100 species with sufficient
> data to describe an annual pattern. The text of the book lists the changes
> in annual abundance patterns, for each species, inasmuch as data was
> available. In each case comment on expected other factors at play are
> offered. Thus there are about 100 different available stories, although
> many
> species show similar annual changes. When seen in a fuller context it is
> clearer.
>
> Philip
>
> -----Original Message-----
> From: Birding-Aus On Behalf
> Of
> Martin Butterfield
> Sent: Thursday, 21 December, 2017 9:18 AM
> To: Penny Brockman
> Cc: birding-aus NEW
> Subject: Re: [Birding-Aus] Parrot population data and a question for
> birding
> aus members
>
> I have looked at some data from the COG Garden Bird Survey (which includes
> measures of both numbers of birds x species and number of observer weeks)
> for Crimson Rosella and Gang-gang Cockatoo in the broad Canberra area. The
> data covered the first 30 years of the survey.
>
> To my surprise adjusting for observer effort doesn't affect the pattern of
> numbers recorded greatly. April-May is still well above September-October
> for both species. So other factors must be in play.
>
> Martin Butterfield
> http://franmart.blogspot.com.au/
>
>
>
> <HR>
> <BR> Birding-Aus mailing list
> <BR>
> <BR> To change settings or unsubscribe visit:
> <BR> http://birding-aus.org/mailman/listinfo/birding-aus_birding-aus.org
> </HR>
>
<HR>
<BR> Birding-Aus mailing list
<BR>
<BR> To change settings or unsubscribe visit:
<BR> http://birding-aus.org/mailman/listinfo/birding-aus_birding-aus.org
</HR>
|
