Wednesday 14 March 2012

Mortal migrants.

A pleasant morning with much improved sea state (3) and good visibility to the horizon so I decided a couple of hours counting the still sparsely distributed seabirds would be a good option, as I would probably pick up any cetacean activity during the survey as well. The first hour turned up small numbers of Cory's shearwater,  3 Med. gulls, a distant Great skua, and a smattering of the ubiquitous lesser black-backed and yellow legged gulls. As we headed north about 20 nm offshore I noticed a relatively sizeable group of distant larus spp. gulls ahead- about 20 birds in total. They were engaged in typical gull behaviour- some resting on the sea, other small groups of 3-4 birds were squabbling and chasing birds with full beaks, which I presumed was fish or squid. Closer scrutiny however revealed that the birds were engaged in scavenging dead passerines from the sea. I stood at the starboard rail and counted 11 corpses within about 20 metres of the ship over the course of about 10 minutes. As the gulls were busy eating and plucking birds from the sea over a distance out to approx. 400 metres I can only presume that the dead birds were fairly evenly spread over a sizeable area. As some of the gulls were sat contentedly on the sea I had the distinct impression that they were full! It was not possible to quantify how many dead birds were in the wreck - it could have been scores or even hundreds! 

Although this is undoubtedly a natural occurrence it is one that I have never witnessed before on such a scale. I have previously seen the likes of quail crash into the sea and have also seen the occasional meadow pipit and skylark fall into the sea in a strong, persistent head wind. I presume that the long, hard storm over the weekend, coupled with the dense sand and dust caused these migrants difficulties somewhere over the sea. They could have been much further north at one stage and blown back south by the storm. On a brighter note a trickle of northward bound migrants have continued past the ship this afternoon, including a swallow, a blackcap, a black redstart, a couple of alba/yarrellii wagtails and another feral type pigeon.

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