Black Swan numbers

I was recently looking at measures of how one measure common birds in the Mallacoota area, as recorded by eBird.  To my surprise Black Swan came out very high on a measure of aggregate number of birds.  While they are very frequently seen in various parts of the Inlet they are usually in modest numbers (2 - infrequently about 20 birds) which didn't seem enough to get the aggregate up near (eg) Silver Gulls where flocks of 50 are usual.

On looking at the detail this was almost entirely due to 2 reports:

1. In 1985 of 3,500 birds; and 
2. In 2008 of 4000 birds.

These reports are greatly above other reports from this area to the extent that I wondered if Fat Finger Syndrome was involved, leading to 1 (or 2) extra zeroes had snuck in.  My memory was that the greatest number of Swans I had seem on the Goodwin Sands was about 150 birds.  

I questioned the high counts with eBird and the reply was that both reports were by expert birders and Black Swans were known to travel widely so the records were believable.  I decided that I would investigate further and requested a copy of all records of Black Swan in Australia.  (As an aside this turned out to be a pretty hefty file: 5 Mb after zipping and expanding to 45 Mb after extraction.  Even after removing the unnecessary - for my purposes - data fields adding it into ACCESS created a 400 Mb monster, so be wary of big files.)

Before the data file arrived I was speaking to a very experienced birder from Bairnsdale who advised that while the numbers were high they would not be dramatic for some of the Gippsland Lakes where up to 6.000 Swans might be seen.  He thought that the birders who usually monitored these flocks didn't 'do' eBird.  At this point I concluded that the high counts for the Inlet were definitely valid.

When the "all-Swans" file arrived it had 140,000 records!  Removing a few text -heavy fields reduced the size to 11 Mb and I added the file to ACCESS for a little analysis.  The biggest flock of Swans recorded was 10.000 birds at a site in Tasmania.  There were several records of 5000 Swans  (on the same date in 2015 so presumably the same flock) from Lake Wollumboola near Nowra and a number of other records in the range 2000 to 4000 on various dates from that site and Lake Rosine  (Corangamite Shire, West of Geelong).  A bit closer to Mallacoota a flock of 4300 were reported from Cape Liptrap (near Wilsons Promontory) in April 2008.

These records confirm the advice from eBird that such flocks, while remarkable. are not unheard of in SE Australia.  That is supported further by the report of large numbers in the Gippsland Lakes.

However if anyone sees a flock of 1000 or more Black Swans on the Inlet it would definitely be worth reporting on the Mallacoota Birds Facebook group and reporting to eBird or Birdlife Australia (or both). 

After posting a link to this on the Mallacoota Birds FB page I got an interesting and helpful  comment from Gail Hodgson:

I remember a good few years ago when I was kayaking regularly, seeing massive flocks of black swans, just past Goodwin Sands. As I approached they would start flapping their wings. It sounded like a huge audience applauding. I don't know if my observation was correct, but they seemed to appear bi anually, alternating with the pelicans? Sometimes in more remote areas we would find nests. This went on for a few years

Then for some reason the Swans numbers dwindled dramatically. Its lovely to see a few more around lately. I miss those glorious creatures.

Then for some reason the Swans numbers dwindled dramatically. Its lovely to see a few more around lately. I miss those glorious creatures.