The names attributed to birds are often fairly straight forward, for example Pied Wagtail. It's black and white (i.e. pied) and if often can be seen with its tail bobbing up and down (i.e. wagging).
Others are named after their call (e.g. Chiffchaff or Curlew), behaviour (e.g. Turnstone or Treecreeper), preferred nesting locations (e.g. Sand Martin or House Sparrow) or the region in which they're found, such as Mediterranean Gull...but this species is no longer restricted to the Mediterranean regions, it can now be found as far north-west as Donegal.
Also, when you consider the scientific name of this species Larus melanocephalus - this translates to "black-headed gull", which is fair enough as it does have a black-head but then there is Chroicocephalus ridibundus or Black-headed Gull...which has a brown head.
|A Mediterranean Gull in winter....without a black head!|
The scientific name Chroicocephalus comes from the Greek meaning "colour-headed" and ridibundus from the Latin "ridere" to "laugh" so it should be called the Colour-headed Laughing Gull....but isn't there already a species called Laughing Gull? Yes!
Laughing Gulls are found in the Americas and the scientific name Leucophaeus atricilla is from the Greek "leukos" meaning "white" (as in the the term leucistic) and the Latin "ater" meaning "black" and "cilla" meaning "tail". However, Laughing Gulls do not have a black tail.
So hope it's all clear now after reading this...Mediterranean Gulls are actually black-headed gulls. Black-headed Gulls are actually colour-headed laughing gulls and Laughing Gulls are actually black-tailed gulls...even though they have a white tail.