|Subject:||Paucity of Crested Pigeons? - Charts of Rock Dove, Spotted Dove|
|From:||Duncan McCaskill <>|
|Date:||Tue, 28 May 2013 15:31:39 +1000|
The Spotted Dove is certainly increasing, but its numbers are still fairly low. There were 248 records from 28 sites in the GBS form 2011/12, compared to 2,581 records from 74 sites for Crested Pigeon.
Rock Dove (feral pigeon) numbers appear to be fairly steady but they do bounce around a fair bit. The chart shows Riock Dove "A" value for the whole GBS for the last 31 years, plus the "A" values from 2003 for sites that were in continuous operation for the last 5 years.
Crested pigeon average group size does show a decline.
One possible explanation that occurred to me is that the years June 2010 - July 2012 (GBS years are June - July) have been very wet and the Crested Pigeons, being dry land species have found it too wet.
A decline after an exceptional period of growth, caused perhaps by predators or parasites adapting to a newly abundant food source/host also sounds reasonable.
On 28 May 2013 14:54, <> wrote:
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