Friday, 20 May 2011

Raise you ten.

Good and bad; Redshank chick and cracked mud.

Another dry spring is upon us and breeding waders in wet grasslands are suffering; site after site is baked hard and cracked. Teeth are sucked and heads are shaken. “Not much we can do – it’s a dry spring” are the usual comments. Quickly followed by “And predation is really bad this year”.

Well, it is surely no surprise that the two are linked.  Drier habitats result in poorer feeding opportunities for waders and allow mammalian predators easier access to the nests and chicks.  Overall, more are predated. With very dry springs, breeding bird numbers crash as waders such as Snipe, and duck, seem to give breeding a miss.  I’ve looked at a dozen or more sites this spring and those that are performing well (and appear to have less predation problems) are those that remain wet.  So the key is to get the habitat into top condition.

But we've now had several dry springs in succession. There is a lot of talk a lot about climate change, how this might affect wetland reserves and what we can do about it.  The simple answer is that we need to adapt our management to these changing conditions and one solution is to store more winter rainfall where possible.  If just an extra 10 cm of water is held in pools or floods at the end of the winter, what difference would it make?  Well, if it were a breezy, sunny April, up to 5 mm of water may be lost through evapo-transpiration on the warmest of days.  So, on average, an additional 10 cm of water is likely to provide an extra month of wetness and this could make all the difference to breeding birds.  One reserve I looked at had put extra water on ‘by accident’ in one compartment.  It was the best looking area on the site and had a high concentration of breeding birds.  Many sites seem overly cautious about raising winter water levels and even let excess water run away.  Climate change is upon us, we need to be more adaptable and one action is to store more rainfall when it is delivered.

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