Not being at all flippant here, but it occasionally occurs to me that active members on this forum frequently seem to have a more in-depth, balanced view of things, I suspect largely brought about experiences over many years, rather than via what they are told on Google
Long story short, there is a major problem locally with the swan population dying off very dramatically since Christmas, the culprit being lead poisoning, apparently via lead dust, though ducks and fish are unaffected.
In the absence of an alternative explanation, the belief is that this is likely intentional poisoning, though I'm at a loss how people might be targeting the swans specifically at this location without it also harming the large duck presence there, not to mention the fish ... I'm just wondering whether someone on-site may have come across anything like this before over the years and have an explanation?
Linky here:
http://www.bbc.co.uk/news/uk-england-tyne-31709334