The Shags of Bass Rock

I’m going to revisit the theme of colour ringing in this blog and give you another example of how they are used in sea bird research.

Since 1973 the Centre for Ecology and Hydrology (CEH) have been running a long-term study on 5 species of sea birds that live on the Isle of May.  One of the biggest studies of its type in the world, the project involves using colour rings to follow individuals and learn about survival, breeding success and behaviour. One of the five study species is the shag. CEH colour ring over 90% of breeding shags and their off-spring every year on the Isle of May with the aim of establishing where they spend the winter. You can read more about the study here.

Now it might be hard to believe, but Bass Rock is not just home to gannets.  Look closely at the lower sections of the steep cliffs and rocky outcrops and you’ll spot kitiwakes, razorbills, guillemots, herring gulls, fulmars and the beautiful green-eyed shags.

On our first visit over to Bass this year, Beckie and I noticed a female shag (female shags hiss as they shake their heads at you, the males honk) wearing a colour ring breeding up on the prison wall. We couldn’t read the code at time as the ring was at the wrong angle, however the next day we got lucky …


White PSP breeding on Bass Rock – she has at least two chicks in the hole in the wall behind her

It’s not a great photo as I quickly snapped it on my phone but if you peer closely, or zoom in on it’s right leg, you can see it reads ‘PSP’. I excitedly reported the sighting to CEH through their dedicated email address ( and a week later got a lovely reply.

It’s turned out to be quite an exciting record as White PSP hasn’t been seen since she fledged from the Isle of May in 2003. I guess it’s no wonder if she’s been hiding in the prison wall for 13 years!

But our colour-ringed shag sightings didn’t end there.

I’ll save you the long story but on another visit we were locked out of the rock and had an hour to hang around the landings before we could get in. Just as we got settled on the path I spotted a shag with a red colour ring, on a ledge, just a few meters above the sea. I scrambled for my camera and quickly took a picture before it made the leap. It was Red LXA.


Red LXA just above the east landing on Bass Rock

Shortly afterwards by the south landing I spotted Blue AJX and later in the day Green AZE.

Again, I excitedly reported the sightings to CEH and got another lovely reply with details of where and when the birds had been ringed and of other sightings:

Green AZE was ringed as a chick on Craigleith in 2014. It made a trip over to the Isle of May in October 2014 but hasn’t been seen since.

Blue AJX was also ringed on the Isle of May in 2014, it was seen three times during the winter on the May and at St Monans in Fife but again, has not been seen since October 2014.

Red LXA was ringed as a chick on Inchmickery (another of the Firth of Forth islands just north of Edinburgh) in 2010. She was then not seen until 2014 when she had an unsuccessful nesting attempt on the Isle of May. In 2015 she returned to the Isle of May and raised three chicks. Earlier this summer she was recorded on an early nest but wasn’t seen after 9th May – maybe she fancied a change of scenery and that’s why she turned up on Bass in mid-July!

Finding out these little life histories of the birds you’ve seen is so interesting and rewarding and provides extremely valuable information for the BTO, CEH and other researchers working to understand more about the ecology of these birds. So keep your eyes peeled for colour rings when out walking on beaches or visiting seabird colonies and report your sightings!




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