Actually the abundance statistic from the GBS is the “A” value, the one that has traditionally been used for the GBS graphs in the COG ABR and used in The GBS
Reports and BOCG. The R value is, as Duncan indicates, merely the Reporting rate, and has rarely been given prominence in COG information. It is the proportion (in this case %) of observer weeks, at which the species was recorded. This is not abundance, it
in no way uses the available information as to the numbers of birds observed. Although there is an obscure connection between the two statistics. If group size was always a constant (such as always one, which it clearly isn’t), then there is a direct connection.
The GBS Report explores this connection, as a highlight of the GBS.
Philip
From: Duncan McCaskill [
Sent: Tuesday, 6 June, 2017 7:52 PM
To: calyptorhynchus .
Cc: Canberra Birds
Subject: Re: [canberrabirds] Red-rumped Parrot abundance
Summaries of COG's data for each species are available on the COG website under
Our Birds / Bird Info. The Red-rumped Parrot summary sheet is here:
http://canberrabirds.org.au/wp-content/uploads/2015/02/Red-rumped-Parrot.pdf (PDF download).
This graph of the reporting rate from COG's Garden Bird Survey shows a decline to about 2002, followed by an increase back to 1980s levels.
Coordinator, Garden Bird Survey.
On 6 June 2017 at 17:16, calyptorhynchus . <> wrote:
Do the COG databases and other collections support my idea that RRPs have become more common over the past 20 years in Canberra?
