There are always black swans on our estuary, but at certain times of the year there are THOUSANDS of them. When I drove into town today, there was a big mass of them in a few places (the estuary is about 10 miles long).
Maybe it’s their mating season?
(Update: According to Wikipedia, they nest in the winter months, so I guess they are mating and nesting now: http://en.wikipedia.org/wiki/Black_swan)