For wildlife and Reserve staff alike, the middle week of June typically represents the busiest period of the busiest month of the busiest season here at Forvie. We’re now at the very height of the ‘simmer dim’, that midsummer period when it never gets properly dark even in the dead of night, and as a result each day seems to last a lifetime. It’s an exciting but exhausting phase of the year, with people and wildlife all working long hours, and a distinct urgency about proceedings.

One formidable task that occurs during this period of the month is the annual nest census for our Common and Arctic Terns. These don’t tend to start nesting until mid-to-late May, some three or four weeks later than our Sandwich Terns (and fully six weeks behind our Black-headed Gulls), and correspondingly their nest census has to take place later in the season. As with the other species, we aim to carry out the census at the point when the first chicks are due to hatch, at which time the number of nests containing eggs is at its highest. Ideally this would have been at the end of the previous week, but with the weather having been unhelpfully cool and wet, it was delayed until Monday. And not a moment too soon either, as we shall see later on.

Common and Arctic Terns are very closely related, and consequently similar in appearance; even experienced observers can struggle to tell them apart at times. As a result, you’ll sometimes hear birders using the term ‘Commic Tern’ to describe an ‘either/or’ individual, or a mixed flock of the two species. Given a decent view, though, the adult birds are readily separable. Common Tern is the larger of the two species, and is heavier-set than Arctic, with broader wings and a larger head and bill. The tail is shorter too, and the overall appearance slightly gull-like. The wings, seen from below, are dusky grey with a diffuse dark trailing edge, and the orange-red bill has a black tip. Follow me so far? There’ll just be a short test at the end of term…

Arctic Tern, by contrast, is slightly smaller and more lightweight, and consequently rather more elegant, with rakishly slender wings and long tail. The head and bill are smaller than in Common Tern, and along with the longer rear end this makes the wings appear to be set well forward. Seen from below, the wings are beautifully translucent, with a neat black trailing edge, and the bill is a deep crimson, usually lacking in a black tip. Simple, huh?

While I’m not very keen on the modern fashion for making up composite words (such as ‘Brexit’ – ugh), I’m ashamed to admit that ‘Commic’ is one that we do use freely on the Reserve. Indeed, that’s exactly what we do with the nest census: the eggs of the two species overlap a great deal in appearance, so it’s easier to deal with them collectively rather than trying to assign each nest we find to one species or the other. And while I’m also not very keen on slapdash convenience over thoroughness and scientific rigour, we also have to factor in the need to census several hundred nests in a short time. As always in our work, the welfare of the wildlife is the top priority, and in this case we must work quickly in order to keep the birds off their nests for the minimal time possible. So, the ‘Commic’ census it is then!

The tactics are similar to those we use for the Black-headed Gull nest census earlier in the season, in terms of covering the ground as thoroughly as possible, and using copious amounts of flour to mark progress.

The terns’ nests themselves can be quite tricky to find at times. It’s easy enough when they’re nesting on open ground, but many of them settle among dense vegetation, which makes life very awkward in terms of access and visibility. Added to that, the eggs themselves are small, and often beautifully camouflaged too. There’s no doubt that despite our being as thorough as possible, some of them will inevitably get missed. But hopefully not too many!

The slightly delayed timing of the census also made life a great deal more difficult than it might have been. A substantial number of nests already contained newly-hatched chicks, and worse still, some contained no chicks at all, with the hatchlings having already gone walkabout. Common and Arctic Tern chicks are active and mobile as soon as they have hatched and dried out, and they can wander a considerable distance from the nest in a short time. This makes them hard to spot, creating a double-edged problem: you may miss a nest entirely, and worse still, you run the risk of treading on the hidden chicks. Again, the dense vegetation gives them plenty of places to hide, and thus every footstep must be taken with the utmost care.

Some of the individual nests are remarkably beautiful; among my favourites were those occupying little hollows among the yellow buds of Biting Stonecrop, a low-growing hardy plant which thrives in the dry and salty dune slacks.

As well as a wide variation in the choice of nesting site, there is also a huge amount of variety in the appearance of the eggs themselves. On a couple of occasions I found nests containing eggs so different in appearance, you’d think they’d been laid by two different species. But this is apparently not that unusual, especially in Arctic Terns, whose eggs are especially varied in colour and markings.

As with all our monitoring work at the ternery, the most rewarding bit of the day is when you extricate yourself from the colony, and watch the parent birds immediately return to their eggs and chicks. The sense of relief at this point – relief at having got the job done, and moreover relief at having negotiated the colony without treading on any eggs or chicks – is a precious feeling. Commic relief indeed.

After a very long day’s hard yakka, the final score stood at 724 nests. This represents a welcome increase of 103 on last year’s total, following several consecutive annual declines – and once again, a relief to know that our regionally-important population of these struggling seabirds appears to be holding its own this year.

In fact, a long working day was made to feel even longer by the constant abuse – both verbal and physical – meted out by the birds. Having been forcefully struck on the head literally hundreds of times during the census, I must admit to feeling a little light-headed by the end of the job. Arctic and Common Terns are super-committed parents, and their actions in defence of their young are admirable. I just wish I was able to tell them that I meant no harm, so they could save their energy for the real predators!

And then there’s the ‘whitewash’… my poor old bushman’s hat will sadly never be the same again. But it did at least keep the recycled fish paste out of my eyes, as well as saving my scalp from serious laceration from the birds’ needle-sharp bills. Personal protective equipment is essential in this job!

With that job mercifully done, our nest-census work for the 2026 season is now complete – much to our collective relief. Until next year…