Cape Gull, Grafham Water

I broke one of my golden rules today, never go south of the Mersey unless it's into north Cheshire or Wales. 

However some birds do occasionally tempt me to travel south and news of a Cape Gull at Grafham Water in Cambridgeshire was one such bird. It wasn't a promising start though, when John messaged me to give me the breaking news, my initial response was "What the heck is a Cape Gull?". A quick look at the scientific name gave me a clue, Larus dominicanus vetula, it was clearly a race of kelp gull.

I've seen quite a few kelp gulls previously in Australia and New Zealand, but not this race. Cape Gull is the South African race which breeds mainly in the southern hemisphere but which is increasingly common further north and has recently started breeding north of the equator, now as close as Morocco. That last piece of information is an important point that I'll come back to later.

The bird was first identified and news put out yesterday, but photographs have come to light which show that it has been present since at least 2nd August. 

I contacted Ray as soon as I got the news and we made plans to go, but the earliest we could manage was today. This made me a little nervous, because I feared that once the local tips re-opened this morning after the weekend, the bird might change it's routine and disappear during the day and only come back to roost in the evening. That's probably what it would do if it was at Pennington Flash and I really didn't want to be there until dusk to get a silhouetted view in fading light of a bird in the middle of the reservoir. However, if that was how it had to be then so be it, we just had to take our chances or risk missing out on what will undoubtedly be a strong contender for bird of the year.

Fortunately though, and I don't know if this is the reason why it's stayed at the reservoir, it's been feeding on a dead fish on the shore and that's where it was when we arrived.

It was a long slog from the car park to almost the opposite side of the reservoir in spiraling temperatures, but fortunately when we got to the water tower on the dam wall about three quarters of the way round, we found that it had flown closer and landed on the railings as close as 50m away from us. Over the next three hours or so we watched it on the railings or followed it when it flew back to it's fish and had excellent views of the bird, often alongside lesser black-backs and yellow-legged gulls. The heat haze was a problem but not as big as it might have been because the bird was generally so close, but it got unbearably hot as the day progressed.

It's a very impressive bird, as dark or darker than great black-back and intermediate in size between greater and lesser black-backs. I don't know the person who identified this bird or what criteria they used to clinch it, but well done to them. 

At this point I have to put in a disclaimer. I'm no gull expert, the following notes are just my thoughts based on watching the gull for a few hours, studying the photos when I got home and researching the identification from books and online resources. There probably are errors here which I will put right as and when I find them. There might also be wrong assumptions. I refer you back to my initial thoughts when I was told about this bird which were, "What the heck is a Cape gull?". Anyway....

It's a 2nd summer bird, just starting to moult into 3rd winter. We know this just by looking at the primaries in the flight shots of the bird below. The old generation feathers are brown, the new generation feathers are black with white tips as in the adult. With this species (and most 3 - 4 year gulls) that combination can only mean that the bird is moulting from 2nd summer to 3rd winter. If this was, for example, a 3rd summer bird moulting into adult plumage, then the old generation secondaries might be worn but they would not be brown, they would be black with broad white tips. 

It's a very distinctive bird, almost Caspian gull like in some respects I thought. It's noticeably long-legged with a deep chest. It has a very large and advanced bill, almost adult like in colouration. Great black-back at this age typically has a darker less colourful bill, though some can be brighter. Most of my photos don't show the grey/green legs very well, probably because phone scoped photos such as these often look a little washed out, but in the field it was very obvious. This photo seems to have captured the colour well though, and you can also see the greenish colour of the majority of the bill.

A small, dark, beady eye is also a feature of Cape gull.

The bird is currently moulting into 3rd winter plumage and this has only recently started. You can tell this because the old feathers are brown and the new feathers are black. Gulls moult their primaries first, in order P1 to P10. The secondaries start to moult at the onset of moult in the mid primaries, so P4 or P5. On this bird, only P1 and P2 are black and therefore new generation feathers and even these are not yet fully grown, you can see how short they are. Even so, you can see that they have a broad white edge, typical of Cape Gull. Two primaries are missing, P3 and P4 and all of the other primaries are brown and not yet moulted. It actually seems to have dropped P4 since yesterday because I've seen photos from Sunday which show seven brown primaries. 

Given that the bird has only just dropped P4, I'm a little surprised that there has been any moult of the secondaries, yet they've clearly been started for a while because you can see that a few of the inner secondaries closest to the body, which includes the tertials, are also short and black with a broad white edge. This is not particularly obvious on my poor quality photos, but others I've seen online clearly show this. However most of the secondaries, at least 16 of them, are still brown with just a narrow white edge. It will be a few weeks yet before this bird attains it's full 3rd winter plumage. 

There's a potential problem here though, because Kelp / Cape gulls are historically southern hemisphere birds, and if this bird had flown here straight from South Africa then we might expect it to already be in 3rd winter plumage and indeed in the next few weeks it should moult into 3rd summer plumage. 

So does the moult cast doubt on the bird? Absolutely not, because as I said earlier, they have now started breeding north of the equator and this population, which is surely the most likely source of origin of this bird, has apparently adjusted its moult to the northern hemisphere. In any case, it's known that juveniles and long stayers that cross the equator often change their moult to align with the north. 

I'm no expert, but as far as I can see, this looks good for Cape Gull.

Even in the poor quality photo above you can clearly see the two areas of active moult are the inner primaries and the inner secondaries including the tertials, and all of the new feathers are at the moment short with broad, bright white edges, which gives the back edge of the wing a jagged look which is particularly obvious in the photo below.

On this photo you can clearly see the brown 2nd generation secondaries with a very narrow white edge and the new 3rd generation tertials and secondaries at the top.

What a bill! Also note the dark beady eye and lanky look of the bird.

A good look at it's eye.

"Stilt" gull! I've never see a great black-back look like this.

There were plenty of yellow-legged gulls at the reservoir, including this magnificent adult standing alongside the Cape Gull. The occurrence of Cape gull in the UK was predicted by BirdGuides in 2019, and in that article they mentioned that yellow-legged gull was a likely carrier species. I don't know if the latter is present in unusually high numbers at Grafham Water at the moment, but it did occur to me that the recent heatwave in southern Europe and North Africa might have resulted in a movement of these gulls into the UK.

Yellow-legged gull.

Lesser black-back with the Cape Gull.

I've been birding over 50 years and selectively twitching for 40 of those years, and this was my first ever visit to Grafham Water. It was a decent few hours birding even without the star attraction, with lots of yellow wagtails, common terns, a single sanderling and a spotted redshank, plus the yellow-legged gulls of course.

Anyway, I'd survived my excursion "down south" and it was now time for home, which took an hour longer than expected in traffic jams and sweltering heat, and did nothing to make me want to change my golden rule.