While I fully agree with your
suggestion on the seasonal variation, it would go without saying that someone
with a conservation bent would inquire whether the prevalence of the species is
on the up or on the down.
My view is that with these two
whistlers, they abundance is wobbling about over time, with no sharp
long-term upward or downward trends, although the GBS is downish over the
long haul. The data poses more questions than explanations, so it may be better
to ignore it with some audiences.
Editor Annual Bird
Dabb [ Sent: Thursday, 26 April 2012 9:15
Subject: FW: [canberrabirds]
Whistler Reporting Rates
In view of the information
provided by Paul for more recent years, I shall, with Philip’s permission,
choose a slide showing seasonal variation rather than trends over the
years. This has a secure observational basis, and will probably be of more
interest to the audience in any event.
Sent: Wednesday, 25 April 2012 12:09 PM To:
Subject: [canberrabirds] Whistler Reporting
Hello everyone, including whistlers, tweeters, and
I have constructed two graphs, one from the GBS data, and one
from all non-GBS surveys, showing the reporting rates of both Golden and Rufous
I calculated the reporting rates by:
For the GBS survey, counting the number of weeks the species
was recorded each year, divided by the total number of weeks recorded that year,
to arrive at a percentage.
For the other surveys, counting the number of data sheets
recording the species each year, divided by the total number of sheets recorded
that year, to arrive at a percentage.
The two graphs show some interesting ups and downs, including
one would suspect, the effect of the bushfires on Rufous Whistlers. I
leave it to you to make further interpretations.
Editor Annual Bird Report
COG Databases Manager