In non-breeding plumage, the head is less streaked and whiter than Herring Gulls. Juvenile Yellow-legged Gulls are very similar to juvenile Lesser Black-backed Gulls, but tend to be whiter-headed and start to gain a grey 'saddle' on their backs quickly as they moult to their first winter plumage. Immature birds gain adult-like characteristics as they mature over the course of five years with the legs turning yellow and dark grey feathers replacing the brown and black immature feathers.
Slightly larger and darker than a Herring Gull, the Yellow-legged Gull has a southerly distribution within Britain & Ireland.
The species was formerly recognized as species by the British Ornithologists' Union in 2005, even though birders had been recording its occurrence for some years. Increasing numbers of records, including a small number of breeding pairs along the south coast, reflect the expansion of breeding populations on the Continent and in North Africa. Our birds are at the very northern edge of their breeding range.
In autumn and winter birds can be seen more widely, often joining other gulls at feeding and loafing sites.
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
