First-winter Mediterranean Gull: separating it from Black-headed

An adult Mediterranean Gull is one of the easier birds in Britain: a clean white wingtip with no black in it at all, and nothing else in the region looks like that.

A first-winter is a different proposition entirely, because that feature has not grown yet. What stands in a Black-headed Gull flock in October is a bird with dark markings in the wing, a dark band across the tail, and no immediately obvious reason to look twice.

This is the same difficulty in a different family as the one wildfowl present in late summer, where a drake in eclipse plumage has temporarily mislaid every feature a guide illustrates him by, or the one a buteo out of range presents as a juvenile. The identification does not become impossible. It moves to a different set of features, and the question is which of them a first-winter bird actually carries.

Start with the outer wing

There is one feature that resolves this pair completely, and it is worth knowing before any of the others.

Black-headed Gull shows a white wedge along the leading edge of the outer wing — a bright, clean white flash on the outer primaries, visible from above and below, at every age from juvenile onwards. It is the species’ most consistent character.

Mediterranean Gull never shows it, at any age.

So the flight view settles it. A gull with a white outer-wing wedge is a Black-headed Gull whatever else it appears to have; a gull without one, in this size class, is worth working through properly.

The head

The face pattern is the feature most people notice first on a standing bird, and it is good.

A first-winter Mediterranean Gull has a broad, well-defined dark mask running through the eye and back across the ear coverts. It reads as a mask, not a spot, and it gives the bird a distinctly stern expression.

Black-headed Gull in winter shows a small, neat, isolated dark spot on the ear coverts, with a paler and much less structured face around it.

The bill

Bill shape is reliable once you have looked at a few, and it is available on a standing bird at moderate range.

Mediterranean Gull’s bill is noticeably heavier, blunt at the tip, and droops slightly towards the end — a stouter, more downcurved impression. Through the winter the base develops a red tone against the dark outer half.

Black-headed Gull’s bill is slimmer, straighter and finer-tipped, and in winter is dull red with a dark tip.

The rest of the wing

The outer wing settles the identification, but the whole wing is worth reading, because it is what makes a first-winter Mediterranean Gull look like the wrong species in the first place.

The overall impression is of a dark outer wing and a dark bar across the inner wing, separated by a paler mid-wing panel, on upperparts that are greyer and more uniform than a young Black-headed Gull’s. That combination is much closer to the pattern of a young Common Gull than to anything the flock around it is showing, and it is the reason so many birds get called the wrong thing after a brief flight view. What it never includes is white along the leading edge of the outer primaries.

The tail

In flight, a first-winter Mediterranean Gull shows a crisp dark subterminal band across an otherwise white tail. It is clean-edged and obvious, and it is a good confirming feature alongside the outer-wing view.

Ageing beyond the first winter

Mediterranean Gull takes three years to reach adult plumage, where Black-headed Gull takes two, which means the intermediate stages are on offer for longer and are worth being able to place.

Through the first spring, a bird begins acquiring dark on the head, often as an untidy partial hood, not the clean full hood of an adult, while retaining worn brown-toned juvenile feathering in the wing. By its second winter the wing has lost most of the dark markings but usually not all of them, and the bird can show a small amount of black towards the wingtip that an adult would not. That last stage is where confidence tends to overreach in the opposite direction: a bird that is nearly clean-winged reads as an adult with something wrong with it, when it is simply not adult yet.

The adult itself is the easy version. Pure white outer primaries with no black anywhere in them, heavy deep-red bill, red legs, and in breeding plumage a full black hood extending well down the nape. Nothing else in the region combines those.

Listen for it

There is a feature nobody puts in a plate, and on a gull flock it can be more efficient than scanning. Mediterranean Gull has a distinctive nasal, rising call, quite unlike the harsher squabbling notes of the Black-headed Gulls it is standing among, and it carries.

That makes the species one of the more realistic candidates for finding a bird by ear in a mixed flock, which is the same argument the Collins Bird Guide review makes for the app: for a good many species, sound is a shorter route to an identification than plumage.

The confusion nobody warns you about

Everyone expects to compare this bird with Black-headed Gull, because that is what it is standing with. The trap is that a first-winter Mediterranean Gull frequently suggests a first-winter Common Gull instead — greyer, cleaner-backed and more strongly marked in the wing than the ginger-brown Black-headed Gulls around it.

Structure sorts it out. Common Gull has a slimmer, unmarked yellowish or greenish bill and a gentler face with a dark smudged head, not a defined mask, and it is a longer-winged, more elegant bird.

Standing among them

On the ground and side by side, a Mediterranean Gull is stockier, longer-legged and taller than the Black-headed Gulls around it, with a flatter crown and a more angular head. These are relative judgements and they work well precisely because the comparison birds are always there.

That is the practical method for this species: not scanning for a Mediterranean Gull, but scanning a Black-headed Gull flock for a bird that is standing slightly too tall with the wrong face.

The other small gull in the flock

One more species shares these flocks and is worth having in mind, if only to be dismissed quickly. A first-winter Little Gull is smaller again, and its upperwing carries a bold dark zigzag running the length of it, a pattern neither of the other two shows at any age. It is a genuinely different bird, not a close call, and the reason to mention it is that “small gull with dark markings in the wing” describes three species in a winter flock, of which only two are difficult.

The same bird changes through the winter

A first-winter Mediterranean Gull in October and the same bird in February do not look alike, which matters if a flock is being checked repeatedly through a season.

The dark mask tends to become better defined as the winter goes on, and the bill develops a reddish base behind the dark tip, so a bird that was fairly nondescript in early autumn becomes more obviously masked and heavier-billed by late winter. Meanwhile the wing feathering wears and fades, so the dark markings that made it findable in flight become browner and less crisp. The features gaining strength and the features losing it are not the same features.

What a record should say

Since one character decides this identification, a record is worth writing in terms of whether that character was seen.

A bird watched only on the ground, however carefully, has been identified on structure, head pattern and bill shape, all of which are comparative and all of which a large odd Black-headed Gull can approach. A bird seen in flight, from either above or below, has either shown the white leading edge or has not. Saying which of those two records is being submitted costs a sentence and is the difference between a claim that can be assessed and one that has to be taken on trust.

Where and when to expect one

The species has expanded north and west across Europe over recent decades, and the practical effect in Britain is that a Mediterranean Gull has gone from a bird worth travelling for to a bird worth checking flocks for. Coastal roosts and estuaries in autumn and winter are the obvious places, and so are inland gull sites, reservoir roosts, playing fields and urban parks anywhere Black-headed Gulls gather in numbers.

Autumn is the productive season for first-winter birds specifically, which is also when the identification is hardest, since that is when the flock contains young Black-headed Gulls in their own confusing plumage. The wing pattern of all three species involved here is drawn side by side on the comparison plates, which is the form this kind of comparison is best made in: three outer wings next to each other settle in one look what several paragraphs can only describe.

A last note on the eastern edge of the same family of problems. The Kamchatka Gull is the Common Gull’s eastern form, and claims of it in Europe run into the mirror image of the difficulty here: features that are reliable when two birds stand together and unreliable when they do not.

1. 1 The white wedge — a clean white flash along the leading edge of the outer primaries. Black-headed Gull shows it at every age, from juvenile onwards. Mediterranean Gull never does. If it is there, the identification is settled.
2. 2 Dark trailing edge — Black-headed Gull carries dark along the back edge of the outer wing, below the white. The contrast between the two is what makes the wedge so visible in flight.
3. 3 Even dark tip — first-winter Mediterranean Gull has dark on the outer wing with no white leading edge cutting through it. Darker overall, and uninterrupted.