The lonely swan

 
Whatever happened to all the swans on Airthrey loch?  Walking  around Stirling university this evening , the first for some time,  I was shocked to see how little wild life was there.
 
Normally at this time of the year its teeming with all kinds of birds. Last year there were seven pairs of nesting swans. Today I didn’t see one. And at the height of the summer there were nearly 20 swans there after all the eggs had hatched.
 
So, what’s happened? Is it anything to do with the notices on the bank informing people not to go into the water or allow children or pets to do so because of blue algae and its potential for causing serious illness even death to animals. Does this apply to birds? 
 I googled it. This is what I found. 
 
 Swan deaths from blue algae
American research

If this is due to pollution it is a devasting blow for the swans at Stirling university.