Shag/Gull relationship?

I'm a commercial fisherman on the West Coast of Scotland (Inner Hebrides).

During the course of my working day I normally pass rocks which Shags (and sometimes a few Cormorants too) sit on. These are not their roosting/nesting areas, but lower-lying rocks that they use to presumably rest/digest/dry their wings on.

I have noticed that there is almost always a single Great Black-backed Gull on the rock amongst the shags. I would say 95% of the time there is a gull in attendance. Always just a single gull, never more.

My question - Is there any confirmed relationship between the two species? If not, would anyone like to speculate why this occurs? Is it simply that they prefer the same spots?


  • That's a very interesting observation, Neil. I've never heard of any particular relationship between these two species but living as I do in the the south of England I'm not best placed to know.
    It could be as you suggest a convenient place to rest. The only other thing I can suggest is that it's to do with food.
    Some of the larger gulls and birds like skuas are well known for harassing smaller sea birds to drop and steal their catch. I think this mostly happens during the breeding season but could it be happening at other times? I've not seen Shags fishing but I assume they would swallow their catch straight away or do they bring it back? I'm sure you would know their behaviour better than me. Could the GBBG be trying to get the Shag to regurgitate its food and steal it?
    Pure speculation on my part I'm afraid. Hopefully, someone else will have some suggestions.



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  • Like Tony, I can only speculate. I've not heard of any relationship between shags and gulls. Perhaps it just follows the shags on their fishing trips, expecting them to find fish more easily that it can, but I would have thought that would attract more than one gull. Maybe the salient point is why is there only one gull, which may suggest something territorial. I have seen gulls just sitting on low rocks and while they don't look like they are actively hunting, they will take any crab that dares to show itself. Maybe this one has found a good spot amongst the shags and doesn't want any competition. If there aren't many other Great Black-backs around, nothing else will be big or brave enough to intrude and the shags won't offer much competition.


    Nige   Flickr

  • Like Tony the only reason I can think of is that the GBB Gull is wanting to rob the Cormorant of its catch. Great Black Back Gulls will tackle quite large birds,we once watched one try,and almost succeed, to drown a drake Mallard for what as far as we could see no reason at all. It is a very large and strong bird and quite aggresive at times.


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