As part of a collaborative project between the Centre for Ecology & Hydrology and the University of Aberdeen we are using resightings of field-readable colour-rings to locate shags in winter to discover more about where they go outside the breeding season.

On the Isle of May, Fife, large scale colour-ringing of shags has been taking place since 1997. Each year the majority of chicks on the island have been ringed with a BTO metal ring and a coloured plastic ring engraved with 3 letters. These colour-rings enable individuals to be identified in the field using binoculars, a telescope or camera zoom (see photos below). As they are a coastal foraging species and because they spend time during the day roosting along the coast it is possible to see colour-ringed shags of all ages on rocky outcrops and harbour walls.

TWX (BTO 1459462) – ringed on 10/7/13 on the tiny island of Craigleith (Firth of Forth), resighted several times on the Brigg in Nov and Dec 2013 (c Mark Pearson)

In the last 4 years intensive colour-ring resighting outside the breeding season, throughout the winter season (September to March), has meant that thousands of individuals have been identified all along the UK coastline, as far north as Yell, Shetland, and as far south as Brighton, Sussex. We have also received several reports of individuals reaching France, Belgium and the Netherlands!

So far, this long-term resighting data has shown that birds aged 2 years and older either stay at the breeding colony year round or disperse to different areas along the coast in the autumn and winter months. The challenge now is to understand why these differences occur and investigate whether winter location is important in determining how well birds survive and/or breed.

Since 2009, shag chicks at other breeding colonies between Fair Isle, Shetland, and the Farne Islands, Northumberland, have also been ringed in order to see if the results from the Isle of May apply at other colonies. We are also very interested to see what individuals do from different colonies during the first few years of life. Last year we received 8500 resightings of over 3200 colour-ringed shags; four of these individuals turned up at Filey Brigg!

Table: Colour-ringed individuals that were seen at Filey Brigg during the 2012-2013 winter season:

All of the records from Filey were of shags that had travelled over 200 km south from where they had been born. Of the four birds recorded so far, two were dead and two were alive.

Before being found at Filey, Blue UHl had only been seen on the Isle of May suggesting that this individual had initially remained close to the colony where it was born. However, the weather in late 2012/early 2013 was exceptionally severe and it is possible that the bird moved south out of its usual wintering area in an attempt to find better conditions. Sadly this strategy did not pay off and it was found dead in February 2013. Blue IUH was never seen alive after it fledged so we know nothing about what it did during the 17 months before it too was found dead at Filey during the spell of bad weather.

Red LRT was resighted three times last winter. First on the Farne Islands on 4th September after which it moved south (approx 350km) to Cromer, Norfolk, where it was seen on 6 November before moving back north to Filey, where it was seen on 14 December. Without the kind help of observers we would never know it had made such an interesting journey!

Red LXT was ringed on Inchmickery in the Firth of Forth during the 2010 breeding season and seen that autumn at Earlsferry, Fife on 23rd October. The following summer it was back on Inchmickery but moved south during the 2012-2013 winter and was seen at Filey. So far there have been no reports of Red LRT or Red LXT this winter – so please keep your eyes peeled, we’d love to know where they are!

We are always grateful to hear of resightings of colour-ringed shags, especially from the English coastline. Please email Jenny Sturgeon at shags@ceh.ac.uk with resightings (including date seen, location, 3-letter code and ring colour) and get in touch if you are interested in getting more involved!

Jenny Sturgeon