Paucity of Crested Pigeons? - Charts of Rock Dove, Spotted Dove

[Duncan McCaskill <>]

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.

Duncan

On 28 May 2013 14:54, <> wrote:

And perhaps, what looks like, on the south-side of Canberra, at least, an increase in Feral Pigeon (Rock Dove) numbers.

Bruce

 

From:

Sent: Tuesday, May 28, 2013 10:52 AM

To: ; m("gmail.com","duncan.mccaskill");" href="" target="_blank">'Duncan McCaskill'

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Subject: [canberrabirds] Paucity of Crested Pigeons? - GBS Data from continuous sites

 

I agree with both that it looks genuine, as in widespread. What does the graph show in respect of the G values over the years?

 

I would be surprised if Spotted Doves has anything to do with it at this stage, as they are still comparatively rare here and they don't compete for nest sites. Maybe food competition from parrots is a factor. Though I still go with that it is normal for a species to decline a bit after having gone through a huge increase in population. No huge rate of increase of anything is ever sustainable indefinitely.

 

Philip

 

-----Original Message-----
From: martin butterfield [
Sent: Tuesday, 28 May 2013 8:34 AM
To: Duncan McCaskill
Cc: canberra birds
Subject: Re: [canberrabirds] Paucity of Crested Pigeons? - GBS Data from continuous sites

Duncan 

 

I agree that it looks like a genuine drop, and from your graph yesterday, a widespread one. 

 

Hopefully some of the biologists in this group will be able to suggest reasons for this.  The kite I would fly is to note that one of the problems with Spotted Doves invading Alice Springs was their competition with the native pigeon species.

 

Martin

On 27 May 2013 22:42, Duncan McCaskill <> wrote:

 

Here is another chart showing the Crested Pigeon "A" value from 2003 to 2012.

 

The red line for the whole GBS. The blue line is restricted to sites that were operating all 5 years before 2012 (from 2008). That is 49 sites from 2008 onwards, but dropping down to only 25 sites for 2003. It looks to me a lot like a real decline.

 

 

 

Duncan McCaskill

GBS Coordinator.

 

 

On 27 May 2013 17:25, John Layton <> wrote:

As I watched a group of Eastern Rosellas feeding among oak mast not far from home during the weekend, they were joined by a lone Crested Pigeon. It struck me that I’ve seen very few Crested Pigeons in the vicinity for several months. Certainly none of the large 30 to 40-bird flocks that were prevalent round here previously, and very few smaller groups/flocks. Perhaps this may be because they’ve spread further afield due to greener pickings since the drought.  Has anyone noticed a similar reduction in their numbers?

 

John K. Layton

Holt.

 

 

--
Martin Butterfield

http://franmart.blogspot.com.au/