Hi Simon, personally Ive got to agree with Tony on this one, Black-headed Gulls mob and rob Coots! I havent seen any evidence myself of them living in harmony, but plenty of behaviour supporting the mobbing and robbing. Seen it at Sale WP, Debdale Park and Crosby Marina. Thats only speaking from my experience of course.
On two seperate occasions this year whilst fishing in Shropshire I have observed Black-headed Gulls "robbing" Coots which had dived to pick up anglers baits in seven foot of water. The Coots as one may imagine were not happy as they had to lose their meal occasionally. On some occasions the coot would come up to the surface and fly straight under the nearest overhanging willow to enjoy their meal or they would resurface several feet from where they had dived this ploy certainly confused the gulls to some extent.
It was evident to me that the gulls had learnt the behaviour and wait for the Coot to surface and then try to steal the meal.
The gulls would slightly outnumber the Coot and then it was pot luck if they stole the meal or not.
On the two visits to the fishery my observations were that there was no harmony involved just gulls robbing the Coots and indeed as usual trying to rob each other.
Coot numbers vary on the fishery between 6 to c20 the Black-headed Gull numbers are very variable but they did not outnumber the Coots to any great degree.
I am sorry I have not been able to answer any of the questions posed in the original post.
It would be very interesting to read any other similar experiences people may have observed regarding this type of behaviour as it was fascinating to witness.
At the shallow end of the lake at Sale Water Park we observed numerous pairings of coots and gulls. The coot dives and surfaces with some vegetable matter which it sets about eating while the gull picks around close by for left overs. The coots seem to tolerate the gulls and the gull makes no attempt to rob the coots meal or get so close as to cause a conflict. This pattern is repeated over and over by many separate pairs across the water so that a neatly spaced pattern of pairs forms with a minimum distance between them. When the inevitable dispute breaks out it is between coots and instigated by non-paired coots with the gulls un-involved. After the disturbance the coots return to their partners and continue to feed peacefully. Questions ... do the pairings last beyond a few minutes / hours /days? Is it possible only when food is abundant? Do the gulls give an advantage to a paired coot by preventing disputes arising so often with other coots? Does the gull simply get a free meal? Symbiosis or parasitism? Has anyone observed this and come up with any good explanations? Has it been described / researched elsewhere?
