30 May 2017

Drift migration in action

Following a brisk overnight easterly wind, hopes were high on the morning of 12th May for a few drift migrants arriving at Isle of May Bird Observatory in the Firth of Forth. The highlight was a stunning male Red-breasted Flycatcher found on the beach at Pilgrims Haven, soon drawing a fair crowd (by island standards). It was quickly noticed that the bird was ringed, and knowing it hadn't been ringed on the island, attempts were made to read the ring from photographs. The ring inscription looked foreign, but unfortunately the ring number itself couldn't be read.

So the bird was left to feed for a couple of hours, before ringers returned with a single-shelf net and just minutes later the bird was caught, revealing the ring was from the Swedish Ringing Scheme. After processing, the bird was released in the same spot and was still present the next day.

Being such an unusual record (we've only ever seen one previous foreign-ringed Red-breasted Flycatcher in the UK - details here), a quick flurry of emails back and forth across the North Sea soon revealed the details. TV0721 was ringed just a week earlier (5th May) at Torhamn in southern Sweden. It had presumably been caught up in an area of high pressure over northern Europe, creating an easterly airflow across the region. The synoptic chart (below) for 11th May also shows the ringing and finding locations, some 1,175km apart!

When ringed, the bird weighed 10.0g and a week later 9.7g, so rather than being thought of as a lost vagrant, it should perhaps be considered a drift migrant, carried on the wind on its migration north. Red-breasted Flycatcher breeds from eastern Europe across to the Himalayas, wintering in southern Asia, although it was long been suggested that there may also be a wintering population in west Africa.

Previous recoveries in the UK have all been in autumn, although one record did see a bird ringed on Shetland recaught in southwest Norway two weeks later!

Many thanks to Anders Loell who got in touch with some background (and a photo) on the ringing of this bird: "I had the pleasure of finding it in a net here at Torhamn. And as you suspected there were some heavy eastern winds. There were only two nets possible to use on the 5th and the only reason why they were active was due to some schoolkids coming out here to visit the observatory."

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