Water watch
 In the next two articles we contrast some of our most welcome wetland sights - herons and egrets - with some of our least welcome - invasive exotic aquatic plants.

Herons and egrets
In the early spring, grey herons start to build their nests, often at sites that have been used for many generations. The majority of heronries are in old broadleaved trees at the edge of estuaries, but a few are found in reedbeds or conifer plantations. The number of heronries in Cornwall has always been rather small: at the present there are probably about 15, containing about 100 nests. Despite the fact that they are few in number, this is such a large and notable bird, with prominent traditional nest sites, that herons and heronries are watched and enjoyed by a wide range of people who appreciate the countryside. Now another member of the heron family also breeds in the county. For many years the little egret has been expanding its range northwards in Europe but it has only recently reached Britain. This strikingly white bird with black legs and yellow feet is a beautiful


addition to our wetland fauna. Until the early 1980s the little egret was both nationally rare and a very rare bird in Cornwall, not recorded in every year. In the summer of 1989 the number of little egrets suddenly increased. From only one in June there were as many as 33 in August and for the first time several overwintered. While there were some indications of breeding as early as 1993, it was only in 1997 that breeding was confirmed. The first breeding attempt took place in an oak tree adjacent to a well-established heronry. It is quite possible that little egrets are now breeding at several sites in the county and the expectation is that they will continue to increase. Paul McCartney Remember to make all of your records count by sending them in to us at the Environmental Records Centre for Cornwall and the Isles of Scilly (ERCCIS).



Grey heron
Photo: JB and S Bottomley
Invaders

I recently received this tongue-in-cheek e-mail message from Trevor Renals of the Environment Agency: "Glad to see the Trust is highlighting the threat to our biodiversity from alien invasive species on the cover of Wild Cornwall, number 86, autumn 2001 (three-cornered leek crowding out our bluebells). If you wish to continue with this theme, I attach some images of Japanese knotweed and parrot's feather that you may find useful." Well spotted, Trevor! I had thought twice about using that picture but		 our tight print deadline had not allowed further search for a fully native version. It's a good point, and one that bears heavily on wetland conservation. Parrot's feather, Australian swamp stonecrop and floating fern (Azolla) are three of our biggest foes. They carpet our ponds and lakes, smothering the natural species diversity of these habitats out of existence, and they continue to be sold liberally through garden centres. Please do your bit for wetland conservation by not buying them and not moving anything (including spawn and pond weed) from one pond to another. Do contact us if you would like further information on good and bad pond plants.

Mark Nicholson


Coming to a pond near you - unless we do something about it. Please help us curb the menace of parrot's feather and other invasive exotic aquatic plants.

Photo: Trevor Renals