Waterbird diversity

In recent months it has been difficult to find much diversity of waterbirds around the area.  This is reflected in a graph!

The dotted blue line is the number of species recorded each month.  As it varies through the seasons I have removed that source of variability by taking a 12 point moving average, giving the red line.  That shows a peak in Summer 2012-13 and another in Summer 2015-16 - with a very sharp drop in the last two months.

Why is this so?

I believe this to be due to rainfall effects, but they are far from simple.  The correlation between the original series of waterbird species and rainfall is very weak: a coefficient of -0.03!  However when the moving averages are compared the coefficient is quite strong at -70.7 : note the minus!  In simple words, when there is a period of sustained high rainfall fewer waterbird species are recorded.  This is because they spread out to the many water-bodies and become harder to spot.  On the other hand when there is a dry spell a few water-bodies survive and the birds are concentrated in them.

In the current situation waterbirds have basically vanished from South-eastern Australia.  The national birders chatline has had comments from Werribee (Victoria) to Gatton (Queensland) abut how the birds have vanished.  For some reason this has focused on Coots which have dropped from hundreds of (apparently) resident birds to none, or perhaps one or two breeding pairs.  In contrast a report from the Macquarie Marshes includes:

"...a non-birder,  phoned a couple of days ago to say she had justarrived at Macquarie Marshes (Willie Retreat). They  had come from Bourke and had to get there via Warren as the bridge at Carinda is out. She said there was almost continuous water in the roadside drains from Warren up to Gibson Way with birds by the hundreds in every "long puddle". 

Another more effusive report said

"We arrived two days ago in the Macquarie Marshes and I have to say I doubt in a number of continents and more years than I care to specify, I have ever seen anything like the numbers of birds - in the air, on water and whateverlittle land and trees there are. We counted about 70 plus species in little over an hour cruising along a few kilometres of the Gibson Way.

"Magpie Geese and Brolgas sticking their heads up above the abundant vegetation, Hardheads shepherding chicks while a couple of Australasian Bitterns boom in the reed beds. The second crossing east of Willie had a mixed assemblage of Great Egrets, Little Egrets, Straw and White Ibis using the flowing water for some angling while a couple well feed kites and a Little Eagle watched on.

"As far as the eye can see there were V-formations, flocks and mixed species clusters travelling in any direction and making avian air traffic control a serious issue. All this activity was not only visual as a cacophony of grunts and whistles drifted from the floating breeding centres anddistinctive odour of Ibis preen oil wafted through marshes."

 So what appears to be needed is some good rain here to get water into the ephemeral marsh on the Plain and Foxlow Lagoon and then a dry spell out West to get the birds here.

If this inspires folk to think about visiting the area the second report above also includes:

The road up from Warren has significant stretches underwater and it is"critical travellers check the local conditions. Gibson Way is closed as large sections have been churned up. It probably possible to get through but don't expect locals to applaud as you chew through their council rates on diesel for repairs.

So check the situation and be thoughtful of those who live in the area.