NEWSWIRE
ALL THE BIGGEST BIRD NEWS & EVENTS
When is a Yellow-legged Gull not a Yellow-legged Gull? We might soon find out, writes Ian Parsons…
TAXONOMY
The identification of gulls can cause many a birder problems, particularly those birds that are referred to as being ‘large white-headed gulls’. The splitting of the Herring Gull complex into separate species over the past few decades has led to birds such as the Caspian Gull and the Yellow-legged Gull becoming ‘true’ species. But a new scientific paper might be the beginning of a new split in one of these species: the Yellow-legged Gull.
The breeding range of the Yellow-legged Gull is centred around the Mediterranean, and it is a common bird in places like southern Spain and southern France. But an expanding population also exists on the Atlantic northern coast of Spain, where the birds breed on the cliffs that fringe the Bay of Biscay.
The study, recently published in Ardeola – the scientific journal of the Spanish Birdlife partner, SEO – shows that the birds that breed on the Mediterranean coast of Spain are larger than those birds that breed on the Atlantic Biscay coast. The research team took measurements from more than 1,500 birds and, in every variable (weight, tarsus length, wing length, head length and bill height), the birds from the Med were consistently larger.
This result was unexpected; the Mediterranean is a nutrient-poor sea, while the Atlantic, in the Bay of Biscay, is a nutrient-rich one, and therefore any size difference would be expected to be the reverse of what the study has shown. One theory behind this size difference is that the Yellow-legged Gulls of
