Spotted Doves in Canberra: where things appear to be at

From time to time the Canberra Ornithologists Group has a rash of messages about the situation of the Spotted Dove (Streptopelia chinensis ; previously known as the Spotted Turtle Dove or STD) in the Canberra area.  There have been two significant posting to the chatline recently: one reported the efforts to remove the species in the Alice Springs area and the second covered a sighting of 6 birds of this species in Weetangera (a suburb to the NW of Lake Burley Griffin).

A further message suggested that something should be done before the species became out of control here.  It would be nice to think that the local Government would do something but previous messages have indicated that they will not be proactive: they need to be shown evidence that there are adverse impacts from the species (by which time it is too late).  The Alice Springs example does cite adverse effects on some native columbids of that area but neither species is strongly established in the Canberra area.

As Coordinator of the COG Garden Bird Survey (GBS) I have examined the history of the species as recorded through the 29 year history of the GBS, and present some results below in the hope that it might inform the debate.

The starting point is a graph showing the number of Spotted Doves reported in the GBS each year.  (While it is generally good practice to transform these numbers into an indicator 'A', adjusting for differential observer effort between years I found that the graphs of A and the raw numbers were for all practical purposes the same.  In some of the discussion which follows it is more sensible IMHO to talk about numbers so I have used that measure here also.) Click to get a bigger image.

GBS Year 29 ended on 2 July 2010.

Note that these numbers do not attempt to represent the number of birds present in the GBS sites at one point in time.  It is

• possible that within a survey week the birds move and the same birds are reported from different sites; or
• equally possible that the birds don't move and are reported the following week(s) from the same site.  

In most cases 1 or 2 birds are reported at one time, although occasional reports of up to 8 have been received.  It is quite clear from the graph that the birds are becoming much more commonly observed.

To put the numbers in context, in the latest year reports totalled 376 Spotted doves:

• this is 91 birds less than the number of Common Mynas (Sturnus tristis)  reported in the first year of the GBS; and
• Spotted Dove population in Alice Springs is estimated as 8,000. 

The distribution of the sites which reported birds across the ACT is shown in this map, compiled using Earthpoint. 

The 'blank area' in Belconnen is interesting as

1. it was the location of the sighting of 6 birds linked above; and 
2. there are a number of GBS sites in that area (unlike central Tuggeranong or Gungahlin where there are few sites).  

It does appear that the birds are widely distributed.

{In the very popular category "Traps for young players" I will stress that to use this facility in Australia all latitudes must be shown with a leading -.  Otherwise they are treated as Northern Hemisphere, which, in the case of Canberra locations, places the points approximately 900km East of Tokyo!}

There were 88 active sites in Year 29 of which 25 reported Spotted Dove at least once.  Charting the number of weeks at which the species was seen at each site x GBS year shows that even where they are observed, they are relatively infrequently reported.

So it seems we still have a species in small numbers, probably distributed across the urban extent of Canberra-Queanbeyan.  The irregular reports by site suggest to me that the birds are quite mobile.

I will leave it to others to suggest how to go abut eradicating the species but, while a worthwhile objective, it looks a very tough ask.  It is also my impression that this species has got here under its own steam rather than imported by a misguided individual (as was the case with the Common Myna).  So it is possible that the birds removed from Canberra will simply be replaced by others lurking in the hinterland.  That is a very pessimistic note on which to conclude!