Wednesday, 4 August 2010

When is a dry wetland good?

A return to the Ouse Valley this week, firstly looking at the now dry Berry Fen. Temporary wetlands of this nature generally become less productive for
birds over a number of years if they are kept wet, principally because food
resources decline. How often have you moaned about `scrapes' not attracting
birds any more? The aim is to have 2 or 3 highly productive flood years at Berry
Fen in every 5 years or so. These wet years will be good for breeding waders and
waterfowl, as well as passage waders, and hopefully the odd scarcity or two.
In the dry years, the site will be allowed to vegetate and be grazed. This will
replenish the seed resource, and the nutrients released on re-flooding the
vegetation will support abundant invertebrates. So Berry Fen will continue to
attract good birds - but not every year.

And then a look at progress on Ouse Fen. At around 500 hectares when completed, the Hanson-RSPB wetland project at Ouse Fen is set to become the UK's largest reedbed after gravel is extracted. However much of this needs to be imagined at the moment as only the early phases are in place. The photograph above shows the latest phase being landformed. The vehicle on the right is at the bottom of a channel through the future reedbed, the bulldozer is levelling out the base of the reedbed that will eventually be 70 cm under water.

Birds were thin on the ground today; 14 Little Egrets, a Garganey, a Ruff, 2 Hobby, 4 Turtle Doves and a handful of Teal were the highlights.


Paul Tout said...

I realise it's a bit violent and against the orthodoxy but I've often wondered if ploughing parts of these scrapes (from a light harrowing to get a few annual weeds going through to a deep ploughing + harrowing to get some nutrients back into circulation) wouldn't be more effective than the supposed remineralization that takes place when the marshes are left to dry out in summer. The Grumpy Ecologist is old enough to remember the productivity of the back-filled pit sites in the Lee Valley (seed wise) and I can assure you that Italian scrapes (both grazed and ungrazed) that dry out pretty well completely on an near-annual remain close-to-crap compared with the initial boom year or two.

Grumpy Ecologist said...

Completely agree with you Touty, more disturbance would be good. However, many sites become scared of the views of visitors (including birders). Despite your comments on Italian scrapes, I think many European countries manage these temporary wetlands better than we do.