Thursday, 2 May 2013

Gas gun starts spring sprint


After a long cold late winter, spring finally arrived in a wave of migrants, with interesting reports of breeding birds now arriving thick and fast.  Spring also usually means a flurry of site visits for the Grumpy Ecologist and this year has been no different; from East Anglia to the Insh Marshes and across to Wales.   The Nene Washes are always a highlight in the spring.  Reports of a gas gun keeping Cambridgeshire residents awake at night were tracked down to an over enthusiastic booming Bittern in a fenland drain.  The breeding success of waders on the washes has been poor for the past three years, due variously to drought or flood.  Fingers are crossed for a good breeding season this year.  The cold and wet winter has left many wet grasslands in good condition; short swards with a lack of winter growth and brimming pools and ditches.

The trip to the Nene provided evidence of the seasonal changeover.  While 800 islandica Black-tailed Godwits huddled together around the pools, 30+ pairs of limosa noisily ‘wickered’ and chased around the fields.  Snipe chipped and drummed over a feeding flock of Dunlin, Ruff and Ringed Plover. Garganey zipped past the last few Whooper Swans.

Over at Ynys-hir, an early morning visit coincided with an arrival of Wood Warblers, trilling through the woodlands.  Pied Flycatchers and Redstarts were already in good numbers. All three species, typical of these West Atlantic Oakwoods, were seen well from the Ynys-hir canopy hide but the highlight was a Goshawk gliding and twisting through the still bare trees with its entourage of squawking crows marking its passage.  Wood Warblers have declined by 60% in a little over a decade (BBS data), and over a longer period have disappeared from many eastern and southern haunts, yet the reason for this decline is still unclear.  Potential causes include changes in woodland structure, increased predation and a phenological mis-match between egg hatch and the peak of caterpillar emergence. Studies in Wales have failed to point the finger at any of these and indeed have shown that the timing of Wood Warbler breeding can track the annual variation in caterpillar emergence.  Perhaps the answer lies in Africa.

No comments: