19 December 2019

A beach discovery provides more than just a ringing recovery

Owen Williams writes:

I can clearly remember the day I made my first ever retrap: it was 1 March 2008 and I was nearing the end of my training for a Woodcock-specific C permit with my trainer and award-winning ringing guru, Tony Cross. Over the following 11 years I have ringed over 1,800 Woodcock and fitted 60 geolocators on this same site in West Wales - the geolocators were part of the research project by the Game and Wildlife Conservation Trust (GWCT) into Woodcock migration. Recoveries of geolocators are always a massive bonus and my first was on 7 January 2013 when I retrapped a bird that had been tagged during the previous winter whilst the BBC’s One Show was filming a piece about Woodcock on my site.


A tagged Woodcock. Photo by Owen Williams.

Since that exciting night, a further 15 geolocators have been recovered, this represents a 23% recovery rate showing the remarkable site fidelity of the species. However the latest recovery must rank as one of the most unusual ever.

On 20 October, I received an email from Tony Cross informing me that Mark Carter, the former assistant warden on Bardsey Island, and ringer, had found a tag washed up on Aberystwyth beach and asking if I recognised the serial number shown in the photograph attached to his email. If the incredible luck of the tag being found on a shingle beach is not enough, to be found by a person who actually knew what it was and then knew who to ask about it, is truly amazing.


The tiny tag found on the beach. Photo by Mark Carter
I instantly recognised the serial number, confirming it was one I fitted on 6 March 2013. So it was promptly sent to Dr Andrew Hoodless who heads up Woodcock research at GWCT. He then sent it to James Fox at Migrate Technology Ltd the company who made the tag.

There then followed a nervous few weeks whilst we waited to find out if the tag still contained viable data despite being immersed in water for what appears to be a considerable time. The good news arrived on 10 December, when we learned that the geolocator had recorded 18 months of data before the batteries eventually ran flat. The data showed that this Woodcock had made three migration flights between West Wales and Yaroslavl in Russia, each journey being around 2,800 km. The tag ran out of power prior to this Woodcock’s autumn migration bringing it back to Wales, which means that it made a minimum of four migration flights since being tagged.

All the birds I tagged in 2013 were retraps of birds ringed in previous winters; this was because we knew that these were site faithful thus increasing the chances of encountering them back on the site in a subsequent winter and recovering the tags. This particular bird had been ringed as a juvenile by me in the previous winter, so had already made three migrations before tagging, with a minimum of four additional journeys before it died; this Woodcock must have flown at least 19,601 km since hatching. It is possible that this individual could have migrated for several years between the tag batteries running flat and the bird perishing, so it could have traveled even further than this.  

Woodcock migration tracked
We can only speculate how this Woodcock perished, however my ringing site is close to a tributary of the Ystwyth River that enters Cardigan Bay 9 km away and very close to the beach in Aberystwyth where the tag was found. There is no knowing when it perished, but it does appear that this tag has spent a considerable time immersed in water. The fact that the data was still accessible after all this time speaks volumes about the quality of design and engineering that goes into these tags.

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