Getting ready for Big Garden Birdwatch: Getting to grips with gulls (and why Common Gulls are rarely common!)

Now here's a group of birds that can really get heads scratching when it comes to Big Garden Birdwatch: the gulls.

Many of you I know have them on your roofs, some of you have them in your garden, and any schools doing the Big Schools Birdwatch have probably got squadrons of them on their playing fields.

So I thought a quick introduction to them would be timely!

I'm going to start with the headlines:

• there are two species of gulls that are really common in towns and cities: the Herring Gull and the Black-headed Gull
• there is also the chance of seeing one of the black-backed gulls
• and the Common Gull is the most confusingly named gull, because for most of us it isn't common; in fact you would be very lucky to see one at all on the Birdwatch.

So we now need some pictures. As with last week's blog about Dunnocks and House Sparrows, I've been out today and taken photos which show them as we all normally see them, rather than frame-filling, see-every-feather shots.

So let's start with Herring Gull. It is a big gull, about the size of a Mallard.

And here's an adult. White head, mid-grey back, dull pinkish legs, bright yellow beak with red spot:

But the thing that makes gulls rather difficult is that the big gulls in particular take several years to reach this plumage. So you can also see sub-adult birds, with brown speckling still in the wings and a big black mark on the bill:

And you can see birds born in 2017 which are still brown and freckly all over:

Herring Gulls are the main species that hang around beaches and rooftops in many coastal towns, but they also are found in winter on playing fields and reservoirs across the country.

The other common species in towns, the Black-headed, is much smaller, only about the size of a Wood Pigeon (but not as tubby):

The first thing you'll notice is that it doesn't have a black head. That will develop in the next three months.

A very few might be starting the process now, like this one:

But most just have two black smudges: one behind the eye, one above it. Also, compared to the Herring Gull, you're looking at a much daintier bird, with red legs and red bill.

The good news with Black-headed Gulls is that they don't have lots of confusing juvenile plumages, so the only other plumage you will see at this time of year is last year's youngster, which also has the black smudge behind the eye, but has washed out flesh-coloured legs, and some brown speckles but only in the wing.

There is the chance you'll see one of the black-backs. In adult plumage, they are very obvious because the back is very dark. Today all I could find was this one Great Black-backed Gull on my local park - look how big it is compared to the Black-headed Gull:

And then there is the Common Gull. Ah, yes, the uncommon Common Gull. It is common on many estuaries; it is common out on sheep fields on downland; you might see it on the Big Garden Birdwatch, especially the further north you are. But for most of us in a garden context, common it ain't!

Just so you know what it looks like, I had to head onto the downs to find some today, picking around in big, open, rough grassy fields, which they love doing.

Common Gull is like a small Herring Gull with a delicate bill: see if you can spot one among these Black-headed Gulls.

So I hope that sets you up nicely for gull spotting on Big Garden Birdwatch.

• Remember: almost every big one you see will be Herring Gull, unless it has a black back.
• And every small one you see with a smudge behind its eye will be a Black-headed Gull.
• And you'll be lucky to see a Common Gull.

Gull experts may gasp at how I've simplified what is a very complicated identification challenge, but to keep them happy the last photo I've used shows yet another species of gull. It's called the Mediterranean Gull, and it is like a Black-headed Gull but with white wing tips. See if you can spot it; now if you see one of those in Big Garden Birdwatch, then you are very, very, very lucky indeed!