Tuesday, 23 November 2010

Whooper Swans and their food

Loch Skerrols with some of the c.130 Whoopers

The gathering of c.130 Whooper Swans (plus up to 100 Greylags and a few hundred Wigeon) on Loch Skerrols in the last week is because of a larger than usual growth of Canadian pondweed in the loch. This weed was brought over from North America in the 19th century and has colonised virtually the whole of Britain where it can choke ponds and ditches, though its main damaging aspect is to shade out native aquatic plants. It is popular in aquaria, but be aware that it can grow from a single small piece if you throw it out into your pond and can quickly become the dominant underwater vegetation.
The loch shore showing drifts of Canadian pondweed plus swan feathers

Canadian pondweed in the hand
It's fascinating to see the Wigeon gathering around the up-ending Whoopers and then gleaning the broken bits as the swans feed, exactly as they do in Loch Indaal in front of the generating station when the swans are feeding on the underwater Zostera beds there.


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