Waterbird Wednesday week 1 - Black-headed Gull
The Black-headed Gull (Chroicocephalus ribibundus) is the commonest gull in the UK, with around 140'000 breeding pairs a year and a wintering population of around 2.2 million. They nest on waterbodies, coastal or inland, and their nests are of a large pile of grasses and sticks. They tend to nest in groups. They are migratory, and in winter many come across to the UK from the continent. Many colour-ringed birds from mainland Europe have been recorded in this country.
Identification
Black-headed Gulls have 2 age groups, and 5 main plumages. They show less variation than larger gulls, and are therefore easier to age. They can be separated from any other common British gull species by their small size and slimmer, elegant shape. Another feature is the white leading edge to the wing, which isn't seen on any other common British gull, and is present in all plumages.
Juvenile
Juvenile Black-headed Gulls are very brown overall, with black tips to the tail feathers and a dark trailing edge to the wing, which is only seen clearly on the upperwing. The wing has a white leading edge, and distinct brown-black wing coverts. The bill is pinkish with a dark tip, and the legs are pink. The head has distinctive brown markings. From below, the primaries appear dark grey.
1st-winter
1st-winter birds retain their juvenile tail and wing feathers, however now they are worn and have lost most of the brown colour. They have moulted the body feathers and the tertials, making the bird look much "cleaner" when resting. The bill is slightly redder in colour than the juvenile, but still isn't as red as adult birds. It still shows a dark tip. All the body feathers have been moulted and are now the same as adult birds. They have a dark spot on the ear-coverts.
1st-summer
1st-summer plumage is very similar to 1st-winter plumage, as the tail and wing feathers are still retained from juvenile plumage. However, the head feathers have been moulted into the dark brown feathers seen on birds in breeding plumage. 1st-summer birds show a variable amount of white in their brown hood. The bill is now of similar colour to an adult bird's. They have a white eye-ring.
Adult winter
Moving into adult winter plumage, Black-headed Gulls finally moult their juvenile wing and tail feathers. Their adult wing feathers have very few markings - a white leading edge to the wing and a thin black wingtip. The underside of the primaries look dark grey. Other than this, other marking include a dark spot on the ear-coverts behind the eye. The legs are red and the bill is red with a black spot on the tip.
The second image shows a 1st-winter bird (left) and an adult winter bird (right). The 1st-winter's beak is much pinker than the bright red of the adult's, and you can see the unmoulted wing feathers on the 1st-winter, whereas the adult's back is much plainer and neater.
Adult summer
Adult summer birds retain their wing and tail feathers from winter, but moult their head back into breeding plumage. The bill and legs are darker than in adult winter plumage and there isn't a dark spot on the bill. They have a white eye-ring.
Similar Species
Mediterranean Gull
1st-winter
1st-winter Mediterranean Gulls have much more dark feathering on the head than Black-headed Gulls, making more of a "mask" than a spot. The bill is completely dark, as well as being shorter and heavier. In flight, they show a lot more black on the wing than a Black-headed Gull would, and lack the white leading edge. The legs are dark.
1st-summer/adult summer
Mediterranean Gulls in summer plumage have a black hood, as oppose to the brown hood of a Black-headed Gull. The bill is shorter and thicker, and is a much brighter red, with a yellow tip and a dark area just before. An adult summer has completely white flight feathers, while the 1st-summer has a variable amount of black on the primary tips. Both lack the white leading edge seen on Black-headed Gulls.
2nd-winter/adult winter
Winter plumage Mediterranean Gulls have much more dark feathering on the head than Black-headed Gulls, as with 1st-winters. The bill also thicker and heavier. Adult winter birds have completely white wings, while 2nd-winters have varied dark tipping to the primaries.
Little Gull
Adult winter
A Little Gull in adult winter plumage would have completely light wings from above, but from below look darker - a white trailing edge is visible from both angled. They lack the white leading edge seen in Black-headed Gulls. The dark spot on the ear-coverts is much more prominent, and there is also a dark "cap". The bill is black and the legs are much lighter pink, and are much shorter. The bird is much smaller overall.
Adult summer
In adult summer plumage, Little Gulls have a fulls black hood with no eye-ring. The wings are completely pale with a white trailing from above, and from below look dark with a white trailing edge - completely unlike the wing pattern of a Black-headed Gull. The bill is black, the legs shorter and the bird is smaller overall.
Bonaparte's Gull
1st-winter
1st-winter Bonaparte's Gulls have a much cleaner spot on the ear-coverts, and the bill is completely black. The legs are shorter and pinker, and the wing coverts are much blacker. Though the white leading edge is present, it is broken by the black primary coverts. The primaries are pale beneath. The black trailing edge is much more prominent from below than in Black-headed Gulls. Overall smaller and slimmer than Black-headed Gull.
Adult winter
As in 1st-winter, the ear-covert spot is cleaner, the legs are shorter and pink, and the bill is completely black. The primaries are pale from below, making the black tips much more prominent below - giving the appearance of a partial trailing edge. Overall smaller and slimmer than Black-headed Gull.
Adult summer
The most obvious feature in field guides for adult summer birds would be the black, not brown, hood. However this would be very difficult to pick up on in most situations - therefore the pale underwing is probably the most useful feature. As always, the bill is black, and the bird is slimmer and smaller overall. The legs are shorter, and are orange.
