Tuesday, November 27, 2012

Cormorants roosting on offshore windfarm structures

Cormorants frequently roost on man-made structures at the coast and in estuaries including channel markers and wrecks. In the past there have been fewer structures slightly further offshore in coastal waters suitable for use as roosts.  The North Hoyle windfarm, off the north Wales coast in Liverpool Bay, was in the first round of such offshore facilities to be installed in UK waters.

As well as the turbine towers this windfarm had mono-piles with anemometer towers mounted on them at both the western and eastern ends of the array of turbines. The anemometer towers became a roost site for cormorants.

Cormorants roosting on North Hoyle
windfarm anemometer tower (Ivor Rees)
The accompanying photo of the western anemometer tower was taken on 26th January 2006 while benthos samples were being taken for studies on available food for common scoter in adjacent parts of Liverpool Bay. At the time there were 25 cormorants using both the platform at the top of the mono-pile and up the lattice tower. This included the series of protruding arms carrying anemometers.

North Hoyle is in the relatively shallow (<20m), southern part of Liverpool Bay towards which birds from the large colony on the Great Orme would be expected to disperse to feed. With the increasing number of energy installations in fairly shallow coastal waters it would be interesting to know if this is becoming a widespread phenomenon and whether operators take steps to discourage the birds. If un-manned towers associated with tidal turbines also become widespread, the presence of structures at sea might, by reducing the need to return to shore to roost, influence feeding range / energetic relationships in some areas. 

This post was written by Ivor Rees

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