American black tern, Long Nanny

There's been an American black tern summering at the little tern and arctic tern colony at Long Nanny, Northumberland since May 2020. For the first year it was thought to be a 'European' black tern but when it returned to the colony in the summer of 2021, analysis of the photos resulted in the bird being re-identified as American black. At the time of it's arrival in 2020 it was just the eighth record for the UK and the first ever in breeding plumage. I have a particular interest in this subspecies having found the sixth for the UK at Eccleston Mere, Merseyside in 2012 and I also saw the seventh at Dungeness in 2018, but both these birds were juveniles. 

The Long Nanny adult has been on my radar for years but it's a long way to travel just for a plumage tick and despite an array of rarities in that area over the period, I've never got round to going. This week however, I was sort of 'in the area' and with plenty of time on my hands I had the opportunity to go. Even so, it took the appearance of a bridled tern on nearby Coquet Island to finally convince me. 

I'm so glad that I went to see this bird, it was the highlight of the day, eclipsing even the bridled tern. Remarkably this year for the first time it's paired up with a male arctic tern and is sitting on two eggs.

It's just possible that the American black tern didn't actually lay these eggs and that she's acting as a surrogate mother, sitting on eggs laid by a now deceased female arctic tern. This kind of thing does happen, I remember last year watching a ring-billed gull in Scotland incubating common gull eggs, much to the consternation of BOTH parents! However, in the case of these terns, the American black has been seen mating with the male arctic and a warden who has seen the nest close up apparently reported back that the eggs look a little smaller than typical arctic tern eggs. We'll have to wait and see, but the mind boggles when considering what the resultant offspring might look like, assuming that the eggs are viable and that the young can survive to adulthood. 

I can think of a few reasons why these young might not survive, whether hybrid or not. For example, arctic terns feed mainly on fish such as sand eels, which they catch by diving into the sea. The adults bring them back to the nest to feed the chicks. Marsh terns such as American black feed mainly on insects which they usually pick off the surface of the water or in flight. Occasionally marsh terns will catch fish and I have seen photos of this bird carrying sand eels, but can they or will they catch enough to satisfy a hungry hybrid / arctic tern chick? I don't know and I suspect that nobody does, but it all adds to the uncertainty surrounding the survival prospects of the chicks. 

In the photo above you can see that the arctic tern has brought the female a sand eel, presumably as a courtship gift because the eggs haven't hatched yet and this was a nest change over. The American black tern was about to flyoff to feed.

I saw the American black tern fly just twice, the second time was after the nest change over and the bird just flew away to feed never to be seen again. However the first time was during a 'dread' when the whole colony went up for no apparent reason and along with the arctic terns, the American black tern flew around for a few minutes often little more than 5m in front of me allowing excellent views, before settling again. This meant that I didn't need to follow it around with the camera because I knew exactly where it was going to land, so at least I had a reasonable chance of a photo or two. The fact that the nest was only about 7m away from where I was standing also helped.

In the photo above you can see a couple of the features which make this American rather than European black tern, i.e. there is no noticeable difference between the black on the head and the black on the body, and also there is a bright white leading edge on the wing. This latter feature I thought was particularly striking in the field. The European bird has a black head contrasting with a dark grey body and the white on the wing is less extensive.

A white underwing is also mentioned as a feature of American black, but although the photo above seems to show this, in other photos it looks more like grey. Perhaps it's just the light. 

Due to the black rather than dark grey body and the pale underwing, American black in many respects resembles white-winged black tern and you can really see this in the photos above and below.

A scarlet red gape is another feature of American black, but to be honest I've never seen the gape of a European black tern for comparison, plus I struggle with shades of red so it probably wouldn't help even if I had two side by side.

See what I mean about the grey underwing in this photo?

The male arctic tern on the nest.

A few minutes before it's mate arrived for the nest change over, another arctic tern approached the nest. At first I thought that this was it's mate, but it soon became clear that it wasn't as it subjected the American black tern to quite a violent attack. 

Nice view of the underwing! It was a mainly sunny day, but when most of my photos were taken it had clouded over for a while, and at first I cursed my luck but actually I think that the lack of glare helped, especially in shots like this.

Eventually though the intruder was repelled. Hopefully the eggs survived.

Ironically, though most of the attention right now is on the bridled tern, American black tern is much the rarer with records still in single figures. As I said previously, this was just the 8th for the UK whereas there have been 26 records of bridled tern.

Edit 04/07/2024: I've been told that the eggs are apparently infertile.