Monday, 23 April 2012

Philopatry? – no thanks, there’s a drought.

A stilt in Donana - coming to a site near you

Having recently moved home and been starved of internet access, birding and blogging has recently been on the back burner.  However, the arrival of a few Black-winged Stilts in the UK links nicely to my last entry.  Further to the exodus of Glossy Ibis from Donana due to drought in the region, it is likely that, given a fair wind, this spring will also see a bumper crop of Black-winged Stilt sightings in the UK.  The breeding population of stilts in Donana varies from around 50 pairs in dry springs to over 14,000 pairs in wet years.  The North Atlantic Oscillation (NAO) is one of the main cyclical climatic forces that affects the weather of the region.  During positive phases of the NAO, westerly winds increase temperature and rainfall over northern Europe but bring drought to the Mediterranean.  Stilts will normally return to breed at their natal site but when conditions are poor, dispersive  behaviour kicks in and they move north.  A study by Jordi Figuerola showed a clear link between poorer conditions and less breeding birds in Donana and the number of records of stilts in the UK.

Drought is much in the news at the moment.  The wildlife stories are all doom and gloom.  Yet wildlife adapts to such conditions as shown by the ibis and stilts, and such dispersive behaviour will prompt colonisation of new areas.  The drying of the Oostvaardersplassen in The Netherlands in the 1990s resulted in the dispersal of the locally breeding Spoonbills and colonising many new areas.  What’s the odds on Black-winged Stilts breeding in the UK this year?

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