Thursday 29 August 2019

Black Terns 24th August 2019

With a welcome change in the weather to gentle southeast winds, soaring temperatures and full on sunshine it was like the Mediterranean at Farmoor Reservoir on Saturday as everyone donned summer clothing  and sat outside the yacht club to enjoy the al fresco delights of a Hackett's coffee and slice of cake.

We were not the only ones to take advantage of this 'Indian Summer' as the change of weather persuaded Black Terns to embark on a mass movement across southern Britain as they headed south to their winter home in tropical Africa. From Somerset in the west to Essex in the east Black Terns were being reported in large numbers today from many and various inland waterbodies.

Farmoor proved an attractive stop over for some of these migrating terns and an initial thirty soon doubled to an estimated sixty plus. I was at the RSPB's Otmoor reserve when the news came through and rapidly made my way to Farmoor but I was too late to see this large flock of Black Terns as many had departed, doubtless making the best of the weather conditions while they lasted to get as far south as possible.

Nevertheless there were still around twenty five Black Terns, a mixture of adults and juveniles lingering and patrolling up and down on Farmoor One, the less disturbed and smaller of the two reservoirs.

I rather like Black Terns, the second smallest tern to visit Britain. They do not have the  tail streamers of Common or Arctic Terns and their wings are slightly shorter and broader although still imparting an elegance to their flight. Both the Common and Arctic Terns and the smaller Little Tern feed mainly by plunge diving for fish whereas the Black Tern feeds by picking insects off the water's surface or from the air with swoops and glides, in a flight of some buoyancy and grace. 

Black Terns, which formerly bred in England up to the middle of the nineteenth century have not done so since, but breed on mainland Europe as close as France, Belgium and the Netherlands extending northwards to Germany, Denmark and southern Scandinavia and east into Russia. They are, however, still regular passage migrants to southern England in Spring and even more so in Autumn.

I took some photos of the Black Terns as they followed a circular course around the reservoir, always in a loose association, dipping and rising endlessly over water that sparkled in the bright sunlight. They were still at Farmoor in the evening but most had gone the next day. 

They still had a very long way to go.

My grateful thanks to Ian Lewington for pointing out this bird is a juvenile with a displaced primary.
An adult would have symmetrical moult i.e the same primary being moulted in both wings not just one

Adult Black Tern in  almost full winter plumage but still showing traces of black breeding plumage on
its underparts

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