The history of White-headed Pigeons in East Gippsland(ish)

 A recent post to Mallacoota Birds covering a photo of a White-headed Pigeon included the comment "... very interesting to see how far south they are venturing.". The author of that post has subsequently consulted her records and commented "I first sighted White-headed Pigeon behind my Betka Road home 30th September, 1998."

I have attempted to look at the broader recorded history of White-headed Pigeons in South Eastern Australia, using material available through Birdata up to 2014 and subsequently through eBird.  The easiest way to show this is through map images (I have yet to work out how to do this analysis on ebird in a quantitative manner using ACCESS.  When/if I do so I will append the results here.)

A few text comments may also assist.  

• The earliest record in eBird for the Mallacoota District is 23 April 1992, followed by one on 10 February 1995.  Note that this was well before eBird was launched in the US in 2002 and even more before the system was widely used in Australia (about 2014): thus these records probably indicate eBird users uploading their historic records.  For East Gippsland West of Mallacoota the first eBird record at Orbost is 19 November 2004, with Metung getting on the list on 6 March 2006.  Bairnsdale first gets mentioned on 15 November 2008.
•  I don't have ready access to individual records in Birdata so have relied on the maps available through that system zooming in to the fine detail to establish the date of some early sightings.  Going well beyond East Gippsland I find 2 records for Lorne, and one to the West of that town in 2007.  The following map covers Birdata records from 1/1/2000 to 31/12/2009.

The next map shows sites from which the pigeon of interest was reported in Birdata for 2010.  It is  obviously only reported sporadically past  Mallacoota, suggesting these are isolated birds "exploring the boundaries of possibility".

At the broad level of detail the maps for 2011 and 2012 are the same, showing reports from further West.

The trend continues for 2013 ...

.. and 2014.

At this point in history the data entry system used for Birdata reached its use-by date and most birders moved to eBird,  This next map shows eBird records (see note above) prior to 2015.

2020 and earlier, with a few pioneers making it across Bass Strait.

And finally, all eBird records.  Orange pins indicate pins in the 4 weeks ending 16 November 2022

In summary they have moved well South and far West.

I have finally worked out how to express the spread of the species using eBird data. I have calculated the earliest year of records classified to Latitude and Longitude to 0.1 degrees for both.  That is shown in the following graphic.

What it shows is the initial entry point at Mallacoota and then arrival in several locations to the West in the mid noughties.  As a generalisation, the spots from which it was reported earlier in the West are either towns (where birders might live, such as Bairnsdale or Orbost) or places popular for birding (Colquon Forest).