Terns are tough. I realized this anew this week while I was working through a mixed flock of mostly non-breeding terns at a roost on South Africa’s West Coast. The wind was picking up, and my eyes were watering from the sunblock my wife had insisted I apply. The rocks were digging into my back as I lay down awkardly alongside my scope, alternately sketching and spying. When I had arrived a few hours ago, I had gone through the typical mixed tern roost sequence. Right off the bat, everything looked different, and I got too excited too quickly, my mind racing with remote possibilities. Things took a tern for the worst when I started imagining that I had found a major local rarity.
Then, as I started working through the terns in more detail, they all morphed into same species! It was only after a few hours of scrutiny that I started picking up reliable patterns and consistent differences. It is important to take your time when working on tricky bird IDs – no book or app or guide can beat personal field experience. It also became clear that our standard field guides are nowhere near thorough enough when dealing with these troublesome birds. One can’t really blame them: there is a great deal of information to fit into one paragraph and depict in 2 or 3 illustrations/photos. Aaaaanywaaays, as Ellen would say, I thought I would share some of my observations here – to help you not only identify, but also enjoy and understand these remarkable seabirds.
“The flight of the spritely Tinker Bell in Disney’s animated feature is like the flight of the terns…these feathered, almost ephemeral pixies swirl on the wind currents with delicacy and sureness.” – Chris Petrak, tailsofbirding.blogspot.co.za
The problem: Roseantcommic Tern and the Boreal Bias
In a groundbreaking identification paper published in British Birds in 1993, Hume stated that “…identification of Common, Arctic and Roseate Terns in the field still presents a challenge. Many people stick too easily to ‘commic tern’ in their notebooks. It is a pity that the names lend themselves so well to such shorthand, but even those who try harder often struggle. Quite rightly, too, on occasion, as the terns are difficult and sometimes impossible; but given a good enough view they should not be.” Ah yes, the good ol’ Commic Tern – an amalgamation of the words Common and Arctic, and a conveniently noncommital moniker if you’re unsure about which species the bird belongs to. However, this term arose in the Palearctic, where these terns breed, and are typically seen in breeding plumage. So if the Brits, Dutch and Scandinavians struggle to differentiate terns in breeding plumage, what chance does our little Southern African birding community have? Remember, we see these terns mostly in non-breeding plumage, when bright colours and tail streamers are absent, and the birds are fairly quiet, and often far out at sea.
Another major problem for us down here in Safrica, is that all the specialist literature devoted to the identification of problem terns, often in painstaking detail, is written for readers in the Northern Hemisphere – thus the Boreal Bias. So the illustrations you see in your Collins or Sibley are not necessarily what you would see in Africa. This can be particularly problematic when it comes to characters such as the colour of the primaries, which change very rapidly from pale silvery grey (fresh) to blackish (worn). This can void identification characters mentioned in European books, such as the dark wedge on the middle of a Common Tern’s wing, which is a wear-related effect.
Another at best irritating, and at worst utterfly confusing effect of the Boreal Bias, is that the seasonal terminology used in ID articles and overseas field guides is the opposite to what we would use. They talk about “first-winter” in our summer. Their birds “winter” here, but we see them around Christmas in the middle of summer. Their spring is our autumn. Their fall is our spring. This can cause major cons-tern-ation. And just to muddy the waters a little further, we also have one species that breeds here in our winter (and is thus on the same cycle as the non-breeding Palearctic migrants). Plus, we have one species that is a non-breeding winter visitor. Is your head spinning (terning?). Mine certainly is. Hopefully this article, written from a decidedly Southern Hemisphere perspective, will help tern the tables.
In addition to Commic Tern, I think we should be wary of Roseate Tern too. Telling these from Commic Terns in non-breeding plumage can be devilishly tricky. And the identification of Antarctic Tern, which does not wander to the Northern Hemisphere and into European ornithological literature, has been much neglected. Indeed, identification texts dealing with Antarctics are often vague or contradictory. I hope this write-up will help a little, but it is by no means the final word. Perhaps I’ve got something completely wrong, or perhaps I’ve overlooked a useful feature. If so, I’d love to hear from you! So Roseantcommic Tern? You guessed it, Roseate + Antarctic + Common + Arctic.
But first, let’s meet the contenders…
1Common Tern
Common Terns are indeed common, occurring along our entire coastline in summer, with a few immature birds present year-round. Maximum populations may reach 300,000-400,000 in summer, making this our most common coastal tern. The species breeds widely in North America and the Palearctic in the Northern Hemisphere summer (our winter). Ring recoveries have shown that most of our birds probably breed around the Baltic Sea, and especially Finland and Sweden. However, ringed birds have also shown connections between Southern Africa and Norway, Germany, the Nerherlands, Wales, Scotlat, France and Israel. Common Terns from Western Europe migrate down along the west coast of Africa, and those from further east along the East Coast. The species is exceptionally rare inland on migration. By the way, the Common Tern’s scientific name, Sterna hirundo, is also reflected in the historical name “Sea Swallow” for terns.
For a 2-minute glimpse into the Common Tern’s world, check out the video below by Avi Birds:
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ABOVE: A Common Tern in breeding plumage photographed in July in Sweden. Most Common Terns develop only a faint greyish flush below (some are darker though). So there isn’t much contrast with the white cheek. They usually have red bills with black tips (all-black in Asian longipennis). The tail streamers are shorter than or level with the wing-tip. Photo by Stefan Berndtsson (link here).
ABOVE: A Common Tern photographed in June. I would guess this might be an overwintering first-year. If it was an adult, you would firstly expect to see some breeding plumage (full black cap and a slight grey wash below, with longer tail streamers, and red-based bill); and secondly, you would expect to see it in the Northern Hemisphere, not at Jakobsbaai on the West Coast. Photo by me.
ABOVE: A bunch of Common Terns resting. Note their conspicuous black carpal (shoulder) bars and solid black (not speckled) crowns. Photo by Phil Penlington.
2Arctic Tern
Arctic Terns are famed for their incredible migration. Thanks to those pesky Pick & Pay wildlife cards, even toddlers know this. But let’s drop some Wikipedia stats anyways. With the advent of satellite tracking, we now finally have a clear picture of just how insane these little globetrotters truly are. Arctic Terns breeding along the frigid shorelines of Greenland or Iceland migrate around 71,000 km per year. The temptation to multiply this with the average lifespan is too great to resist: 30 years x yearly average = 2.4 million kilometres. Three times to the Moon and back, as the tern flies. Birds from The Netherlands fly even further: down the coast of Europe and Africa, then sho’t left just past Cape Town, and east to Australia or even New Zealand, then south to the Antarctic. One bird holds the record of the longest known migration for any animal: 91,000 km in a year. This species sees more daylight than any other creature, and has pretty much perpetual summer – making its scientific name of S. paradisaea quite fitting. Sick or exhausted Arctic Terns rarely join tern roosts along the coast, but for the most part they are pelagic, and migrate well offshore. They are most commonly encountered in spring and autumn on passage. But expect the unexpected: in September 1996, Dave Allan and Andrew Jenkins found an Arctic Tern flying above Katse Dam in Lesotho, not only 500 km from the sea, but also way up in the mountains!
ABOVE: An Arctic Tern in full breeding plumage is a handsome bastard. They are darker grey below than Common Terns, but not as dark as Antarctics (which can almost recall Whiskered Tern). Most breeding Common Terns would have a dark bill-tip (all-red in Arctic). Note also the very short legs, but long tail streamers extending beyond the wings. It is a small and petite bird, with a short neck, rounded head and short spike of a bill. Photo pirated off MaxPixel (link here).
ABOVE: These are more typical views that we can expect in South Africa, where Arctic Terns are highly pelagic and are very seldom seen ashore. I photographed this bird on the recent BirdLife South Africa Flock at Sea trip, somewhere SE of Cape Town. Even at this distance, you can make out some of the Arctic/Antarctic type features: very long white tail streamers and a pale upper- and underwing. This could also be an Antarctic on the way to South Africa’s shore, or out on a deep sea foraging mission. Photo by Faansie Peacock.
ABOVE: I am unsure whether these are Arctic Terns or Antarctics. Pretty bad pictures but I would have guessed Arctic based on the wing shape, dainty look, short-looking bill and narrow swept-back primaries. I would expect Antarctic to have darker, more worn primries by this time (March)…but the distinction between these two species at such a distance is a stretch. Let me know if you have thoughts.
ABOVE: Circling the entire planet was obviously not for this guy. This is an Arctic Tern specimen that I skinned at the Ditsong National Museum of Natural History. Check out those long tail streamers. The entire tail is white except for a black web on the outer vane of each outer feather (the tail is crossed here). Photo by Faansie Peacock.
ABOVE: I would say these primaries are still fairly fresh. The dark mottling on the carpal area and primary coverts may suggest this is a first-year bird. Common Terns would have darker primaries, and a dark grey bar on the secondaries, not the rather plain grey wing of this bird with a wide white trailing edge. Of course, also note the pure white rump (grey-washed in Common, but also white in Antarctic). Photo by Faansie Peacock.
ABOVE: Arctic Tern underwing. Note the short arm but long, narrow hand. The underwing is very pale overall – in fact, if you put it in front of a light, all of the inner primaries and secondaries are translucent (only the inner ones on Common, forming a triangular patch in middle of wing). Wonder what happened to that blue jersey of mine? Photo by Faansie Peacock.
3Roseate Tern
We do have one breeding species, namely the Roseate Tern. This globally widespread bird is now classified as regionally Endangered, as the South African population size is estimated at less than 250 mature individuals. Worldwide, Roseates breed in North America, Azores, western Europe, from the Arabian Peninsula south to East Africa, on several Indian Ocean islands (including Madagascar), and eastwards to India, the East Indies and into the western Pacific and Australia. So in summary, much of planet Earth. Locally though, they breed only on three little islands off South Africa’s southern coast: Dyer Island (3-20 pairs); and in Algoa Bay off Port Elizabeth, St Croix Island (0-44 pairs) and Bird Island (70-300, average about 165 pairs). The latter island is also of critical conservation importance for its large Cape Gannet colony. By the way, this species is named S. dougallii, after Scottish doctor and amateur naturalist Peter McDougall (1777-1814); he received this honour because he shot some of these terns and sent them to George Montagu (he of the harrier), who described them as a new species in 1813.
ABOVE: So halfway through writing this article, I discovered that my friend Phil had copied a whole load of Roseate photos onto my hard drive many years ago. He might cringe at the quaity of these pics today, but I still think they are pretty spectacular and definitely illustrate this species very well! Thanks Phil. First off, the most important thing with Roseates is that rudely long and clearly drooped bill. This is a breeding bird which has started developing the red bill base, and has a full black cap. They are supposed to have a pink flush to the underparts – I always struggle to see this, but perhaps if you squint…Note also the orange (instead of dark red) legs. Photo by Phil Penlington.
ABOVE: This Roseate Tern is barely showing any red on the bill, but still has a full black cap and orangey legs. This posture nicely shows the very long tail streamers plus the exceptionally long, decurved bill. The plumage is retina-burning white in Roseates; notably more so than in other terns. Better underexpose a few stops. Photo by Phil Penlington.
ABOVE: A great many Roseates sport these green leg flags! This was photographed in the breeding season, so I suspect it’s a youngish bird. It also has a faint dark carpal bar (nowhere near as prominent as in Common Tern). The primaries of Roseates have very strong white inner webs, that form a distinctive pattern. This bird has a full black bill; non-breeding adults do too (as in Common and Arctic, and some Antarctics). Photo by Phil Penlington.
ABOVE: I suspect that this giraffe-neck posture forms part of the elaborate courtship and pair-bonding display of Roseate Terns. Unless I’m misinterpreting it and this is a form of aggression between rivals? The lower two are probably adults, with a first-year arriving. Note how white the wings look in flight. Photo by Phil Penlington.
ABOVE: The outer tail streamers of Rosies are disproportionately long, and they often flap around when the bird is flying. Photo by Phil Penlington.
4Antarctic Tern
Okay, are you still keeping track? We have one localized breeding species (Roseate); one common non-breeding summer visitor (Common); and one rare passage migrant (Arctic). And now the pièce de résis-terns. We also have a non-breeding winter visitor, one of the very few winter immigrants to our region. The Antarctic Tern, Sterna vittata, and the focus of this article. So as their name implies, these terns are the polar opposites of Arctic Terns. They breed on the Antarctic Peninsula, as well as various sub-Antarctic and Southern Ocean islands, in the southern summer. This includes South Africa’s Prince Edward islands; therefore the conservation of that breeding population is our responsibility. After breeding, some of these birds migrate to the coasts of Argentina and South Africa, where they join mixed tern roosts on coastal rock outcrops, offshore islands, small bays or sheltered beaches. The world population is probably in the order of 45,000 pairs and around 10,000 visit South Africa from May to October. The biggest roosts are on islands (e.g. Bird Island, Dyer Island, Dassen Island) with mainland roosts typically hosting fewer than 900 birds (often just a few). The name vittata means a longitudinal stripe, in reference to the white cheek stripe that separates the black cap and grey throat.
ABOVE: This is the map I made for the 2015 Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland (see details here). It shows part of the breeding range of Antarctic Tern and the various subspecies on the different sub-Antarctic islands.
ABOVE: An Antarctic Tern just starting its post-br. moult out of br. plumage as evident by the one or two white feathers on its forehead. It is essentially the Southern Hemisphere version of Arctic Tern, although a little bigger and a lot less migratory. Note the entirely red bill, reg legs and grey wash below, contrasting with the white cheek stripe. Early June, Jakobsbaai. Photo by Faansie Peacock.
ABOVE: An intensely coloured Antarctic Tern (probably a male of the race vittata). This is still pretty much full br. plumage, with the prominent white line on the cheek contrasting with the black crown and grey throat. Unless you see the deeply forked tail, you could momentarily mistake this for a Whiskered Tern. Early June, Jakobsbaai. Photo by Faansie Peacock.
ABOVE: I would say this Antarctic Tern, photographed in early June on the West Coast, is about halfway between breeding and non-breeding plumage. You can see from how black the outer primaries are that these are very worn and will soon be replaced. Photo by Faansie Peacock.
ABOVE: When I initially saw this Antarctic Tern with its exceptionally long tail streamers, I though Roseate. But of course the bill is not nearly long and droopy enough, and would never be all-red in Roseate. That species would also be much whiter, with paler primaries and orangey feet. The feet of this bird have turned dull maroon, but its beak is still solid and bright red even though it is in non-br. plumage. Photo by Faansie Peacock.
ABOVE: On the other hand, many Antarctics at the same time had entirely black bills, or just showed a tiny tinge of red at the base. This bird also has darker legs and fresh primaries. It might be a failed breeder that started moulting early on, or something like a second winter. Note the large, rounded, domed head – very different from Common – and the dumpy shape. Photo by Faansie Peacock.
ABOVE: Antarctic Terns can have really impressive tail streamers that extend well beyond the folded wing at rest. Photo by Faansie Peacock.
Other possibilities
Perhaps it would be prudent to just mention some other possibilities, and a handful of vagrants. You never know right?
| Species | Status | Range | ID features |
|---|---|---|---|
| Whiskered Tern Chlidonias hybrida |
A common breeding species and partial migrant. | Inland wetlands in much of SA. | Quite like a br. Antarctic with white cheek stripe, but darker and almost black on belly (contrasting strongly with white vent); bill and legs maroon. Tail shallowly notched (not deeply forked). Marsh terns (Chlidonias) incl. Whiskered, White-winged and Black, have lazy, banking flight and tend to pick prey from the water surface (do not hover and dive like sea terns). |
| White-cheeked Tern Sterna repressa |
Very rare vagrant. 3 records in N Coast of KZN. | From Kenya to Arabia and India. | Similar to br. Antarctic, but most likely in summer, and entire rump and tail grey. Not easily told from other terns in non-br. plumage. |
| Forster’s Tern Sterna forsteri |
Unlikely potential vagrant. | Breeds N America; winters C America. | Like Common Tern but wing very plain (almost all-white above). Rump white. Tail extends beyond wings. Non-br. has an (almost) isolated black face mask, like a Gull-billed Tern, plus longish orange legs. |
| South American Tern Sterna hirundinacea |
Very unlikely potential vagrant. | Breeds along coasts of S America. S birds migrate to warmer latitudes. | ID not clear, but highly unlikely to reach us. Heavier, bulkier bird with a stronger bill and longer legs. Often white crescent below eye in non-br. |
| Kerguelen Tern Sterna virgata |
Highly unlikely potential vagrant, except if ship-assisted. | One of the rarest terns. Only 3,500-6,500 in the world. On Crozet, Prince Edward and Kerguelen islands. | Sedentary and thus highly unlikely to reach SA. Like Antarctic but smaller (like Arctic), with shorter tail streamers and grey-washed rump and tail. |
Tern taxonomy
The taxonomy of the Antarctic Tern is a bit of a controversial subject. As many as seven races have been recognized in this taxon, but the validity of some of these should be reinvestigated. We reportedly have four visiting us in South Africa, of which the nominate vittata is most common. Apparently, some of our birds are also somewhere between vittata and sanctipauli, and these may be from Prince Edward/Marion, or from the Crozets. Would one be able to identify birds to subspecific level in the field? Perhaps if you’ve spent a lifetime researching, ringing and measuring them, and if your name is Tony Tree or Mark Boorman. I am not sure that I would feel confident enough to make a call. There are some general patterns, as you can see in the table below. Most of our birds are presumably of the nominate vittata race. But a particularly large, pale-looking bird with a bill longer than 40 mm, and tail streamers longer than 180 mm is presumably tristanensis. Conversely, a very small, short-billed, short-tailed bird might be georgiae. I wouldn’t worry too much about all this. It mostly applies to birds in the hand, that can be measured.
In Common Tern, we have two races visiting us: the nominate S. h. hirundo, and the rarer S. h. longipennis. Or more specifically, in addition to the nominate, we probably get intergrades between hirundo and longipennis. In theory, longipennis in breeding plumage can be recognized by its all-black bill and blackish legs, plus overall darker plumage. But many non-breeding Commons also have black bills and darker legs, so it becomes rather tricky while the birds are on our shores. Arctic Tern is monotypic.
Roseate Tern is an interesting one. Up to five subspecies are recognized worldwide, but the variation between these is as great as the variation within the nominate dougallii subspecies. Our birds are currently placed in this race based on their bill colour, pinkish underparts and measurements. But that it is not necessarily correct: our birds’ breeding plumage and breeding season corresponds with those breeding on southern Madagascar. There is a specimen of a breeding adult in the Durban Natural Science Museum that is classified as S. d. bangsi, which breeds from the Arabian Sea to the SW Pacific. Birds of this taxon from the Seychelles have all-red bills (normally black, or red with a black tip in our birds). Roberts VII states the Durban specimen has an all-black bill, but I suspect that is a typo for all-red bill. Again, I wouldn’t worry too much about subspecies – just an interesting aside. I think that’s more than enough taxonomy talk for now. Let’s tern back to the subject at hand.
| Subspecies | Breeding islands | Status in SA | Plumage | Bill colour |
|---|---|---|---|---|
| S. v. vittata | Crozet, Kerguelen, Heard, Prince Edward and Marion | Most common spp in E Cape and on W Coast | Darkest ssp | Blood red |
| S. v. sanctipauli | Amsterdam and St Paul | Uncommon visitor to E Cape and W Cape | Paler | Coral red |
| S. v. georgiae | S Georgia; possibly S Orkneys, S Sandvich, Bouvet | Mostly SW W Cape (whatever that means) | Smallest; slightly paler than nominate | Bright red |
| S. v. tristanensis | Tristan da Cunha Archipelago, Gough | Dyer Island, Bird Island | Large; pale; long-tailed | Coral red |
ABOVE: This Antarctic Tern looks kinda pale and small, with a short bill, short neck, short legs and a short tail (although the latter might just be worn off). Would that make it one of the other subspecies, such as georgiae? Who knows. In fact, this bird almost has a Kerguelen Tern vibe about (just kidding). Late May, Jakobsbaai. Photo by Faansie Peacock.
Timing and moult
Don’t get a skrik when you see the terning circles below. They are intended to help us visualize the annual cycle of (adult) terns, and help us make sense of things like the timing of moult and when breeding and non-breeding plumage is attained. This can be very useful when identifying terns. For example, in Europe a southbound autumn Commic Tern with wing moult (gaps in primaries, ragged trailing edge), would be a Common as Arctics only commence their moult at their wintering grounds. That being said, moult is a very complicated subject, with lots of ifs, buts and exceptions. And to keep us on our toes, moult is especially complex in terns, which can have up to four active moult centres in the wing at any one time!
Some species, such as Common Tern, replace their inner primaries twice. The first wave starts on the breeding grounds or just after departure. The second wave may partly overlap, and starts from Nov-Feb and completes by Mar-Apr. Terns’ primaries are whitish or pale silver when fresh, but quite rapidly and dramatically become dark grey or blackish when worn (often the opposite in other birds). This means that there is often a very strong contrast between new pale feathers and old dark feathers. This causes the dark wedge on the outer wing of Common Tern for example. In theory, the timing of moult would differ between Southern Hemisphere breeders such as Antarctic Tern, and Northern Hemisphere breeders such as Common; but in practice, this is perhaps a bit dodgy to rely on given our present knowledge.
Also keep in mind juveniles. These hatch with highly patterened plumage and gingery tones (see photos below). This distinctive plumage is gradually replaced within a few months. Some faded juvenile feathers (e.g. tertials, wing coverts) may be retained, which would indicate a bird in its first-year, or early second calendar year. Many young birds undergo a second series of moult after their first wing moult, and those that moulted early may even undergo a third wing moult. The bottom line is that we still need to investigate the usefulness of moult for identification. But it is nevertheless very interesting to make a note of the moult stage if you are studying terns. This might help you sort out first-years from adults. In a mixed flock, obvious differences in moult may indicate that a different species is in play. The question is which one?
LEGEND FOR CLOCKS:
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ABOVE: Antarctic breeds on the Antarctic Peninsula and sub-Antarctic islands in the southern summer – you wouldn’t expect it to hang around there in the dead and dark of winter would you? No, instead it heads north to our sunny shores. Arrival, departure and peak times differ for the West Coast and Eastern Cape, but in general the first arrivals are in late April and early May, when many still sport glorious breeding plumage. They are gone by October, although a very few immatures may linger until November or even as late as March. These would probably remain overlooked in the flood of Common Terns in summer.
ABOVE: Common Terns start their complete post-breeding moult quite early on (compare Arctic Tern). By the time they get here, they are in non-br. plumage and might already be on their second wave of primary moult. But they are also quite late in attaining their (fairly demure) br. plumage. Some have the full black cap from March onwards; others only from May. Many thus leave us while still in non-br. plumage. Young birds attain full adult plumage in their third year, but often show partial br. plumage at the end of their second year. Each moult cycle takes around 6-7 months. The tail may be moulted twice in one season.
ABOVE: Roseate Terns are present in South Africa year-round. They arrive at their breeding colonies in June and depart in October; after breeding they disperse along the coast, as far north as the Saldanha area on the West Coast, and eastwards along the shoreline of the Eastern Cape. They assume breeding plumage, with a full black cap, from late April; the forehead turns white again by November. Breeding birds also have pale pink underparts, which are moulted to white by January. Primary moult may partly overlap the chick-feeding stage, and start as easly as late August. The second moult wave, during which the inner primaries are replaced again, starts around Jan/Feb. The bill is black for most of the year, but during active breeding it turns orange or reddish with a black tip, then fades to pink and back to black after the chicks fledge. Juveniles may visit the breeding colony from one year old, but most only start breeding in their third or even fourth year.
ABOVE: Arctic Terns’ clock is almost the precise opposite of Antarctic’s. The two species occur side-by-side in the southern summer: Antarctic doesn’t penetrate further N than about Lambert’s Bay, but Arctic “winters” in the Southern Oceans alongside breeding Antarctic. Arctic breeds a bit later than Common and starts its primary moult only after arrival on the non-breeding grounds from Sep onwards. This takes about 5 months and finishes in Feb-Mar. The tail is moulted only once. Juvenile start their body moult during migration and retain only their juvenile scapulars and tertials from late October. Juveniles’ body moult is done by Feb, but wing moult only starts in mid-summer and finishes up in May-Aug. Arctics are mainly passage migrants that cruise past South Africa. Westerly winds blow some closer inshore, and sick or tired ones may join coastal roosts. Numbers peak on southward passage, Oct-Dec. Very small numbers may linger throughout the year (presumably first-year birds).
Identification by size, shape and struture
Although stats don’t really tern me on, I spent a few minutes fiddling with the biometric data from Roberts VII to come with the accompanying graphs here. They shouldn’t be taken as gospel (often a lot depends on the measuring technique used, the age of the bird, and the time of year, e.g. whether the tail feather are fully grown or not). But they do give you some idea of the relative proportions of Antarctic, Arctic, Common and Roseate Terns. For Antarctic, I also plotted races.
Bill dimensions
Despite a lot of overlap between the species, culmen (bill) length can a very useful feature. Arctic Terns are decidedly short-billed, with a spikey bill that gives them a cuter appearance. On the other side of the spectrum, Roseate Terns are obviously long-billed, with long, thin, sharply pointed beaks that droop obviously. Common and Antarctic are somewhere in the middle. Bill length is very similar between them, but Antarctic seems to have a slightly thicker, stubbier, stronger-looking bill on average.
Leg length
Leg length almost mirrors bill length. Arctic has very short legs, almost appearing leg-less, and Common has the longest legs – usually notably longer than Antarctics in direct comparison. Beware though, as birds with their belly feathers fluffed up appear shorter-legged, while alert birds with their plumage sleeked down appear longer-legged. Roseate also has relatively long legs, close to Common.
Tail streamers
The length of the streamer on the outermost feather on each side of the tail can be useful, but note that these thin, delicate streamers are easily broken and wear off with time. They are present in breeding plumage, and are either shorter or partially grown in non-breeding plumage, depending on whether the tail is moulted once or twice per year. It is best to evaluate the length of the tail against the folded wing-tip. Roseate has the longest streamers, accentuated by its relatively short wings. This gives Roseate a very streamlined, sleek, long-tailed look in flight. Arctic has long streamers that clearly extend past its long wings at rest. Common, despite having proportionately shorter wings than Arctic, has short streamers that fall short or level with its wing-tip. Antarctic can also have exceptionally long streamers (depending on the race), but even in non-breeding plumage the streamers often (but not always) extend well beyond the folded wing. On the graph it looks like Common has a longer tail, but remember that it also has relatively longer wings, so the tail does not project as far as Antarctic.
Wing length
Arctics have surprisingly long wings considering their small size. In fact, because of this they look longer-winged than Commons, although the average is very close. Specifically, Arctics have shorter arms but longer primaries, and narrower wings, giving them a more delicate appearance. Common has the longest wings, on average, of the bunch. Roseate has surprisingly short wings. Indeed, in flight it looks markedly short-winged and long-tailed. Antarctic has quite short wings, presumably because its migration is so much shorter.
Jizz: the picture as a whole
Arctic looks small and petite, with a fat body but attenuated rear thanks to the long wings and long tail streamers extending beyond the wing. It also looks squat, due to the very short legs and small, rounded head resting on a short neck (right in the shoulders), and the spikey bill. Roseate is the other extreme: very long rear, with exceptionally long, elegant tail streamers and a long, sharp, clearly drooped bill. Its crown looks long and flat and the forehead slopes gradually into the bill. Overall, it looks exceptionally sleek, elegant and elongated; this is somehow complimented by the extreme whiteness of its plumage. Common has average proportions, with tail streamers short of or level with wing-tip, relatively long legs and a longish neck. Its crown is relatively flat, with the forehead (in front of the eye) often the highest point, and the rear crown sloping down from there. Common looks less heavyset than Antarctic and it carries its weight more in its chest. Antarctic Tern looks bigger-headed, with a more rounded crown (or at least with rounded angles). Typically the highest point on its head is behind the eye. Its forehead is steeper than in Common, angling down more sharply to its bill-base. Antarctic is often said to be distinctly dumpy; its weight is more in its fat belly and its legs are somewhat shorter than Common’s. Antarctic is a touch bigger than Common. For Vaalies (inland birders), it might be useful to compare to the marsh terns. Antarctic has the dumpy, powerful build and relatively strong bill and big head of a Whiskered Tern; whereas Common reminds one more of a White-winged Tern, with its thinner bill, small head and more black-and-white plumage.
In flight
Arctic Terns look light, free, bouncy and delicate in flight, at the mercy of the wind, with fluttery, butterfly-like strokes and a slower downbeat but a quick upwards snap. It has long primaries that taper into a sharp, slightly back-curved tip. Arctic’s wings appear to be set more forwards than in Common, which, together with its long tail, make it look as if there is more behind the wings than in front. It has a short ‘arm’, but long ‘hand’, and is thus less cross-shaped. Common is the opposite: its wings are centrally placed, and its tail is shorter but its neck longer. Its wings are slightly broader, and its ‘hand’ more triangular with a blunter tip. Its arms are longer but its hands shorter; thus more cruciform in shape. Commons fly more steadily, with a fast powerful downstroke. Roseate looks short-winged in flight, but very long-tailed – the long streamers often flapping around in the wind while it flies. In his 1993 paper (much quoted here), Hume compared it to a tiny tropicbird! It tends to fly straighter, faster and more purposefully, with equal emphasis on the up- and downstroke and a stiff-winged look. To be honest, I haven’t looked at Antarctic in such detail [insert your experience here]. To me their wings look quite broad, with about equal length arm and hand, and the slight backwards curved primary-tips of Arctic. Being an overall rather heavy bird, its flight is not particularly light.
Behaviour
The various species seem to be quite aggressive towards each other in mixed roosts, and they tend to stick to their own sort. This often results in all the Commons sitting together and all the Antarctics in a different area. But there is also some mixing, and older or breeding birds tend to be antagonistic even towards their own kind. Antarctic forages mostly by plunge-diving after anchovies and other small fish, but also surface-dips at times. Common Terns plunge-dive by flying along, stopping, swooping up, perhaps hovering briefly, and then diving down. Arctics are more hesitant: hovering, repositioning, hovering again, dipping partway, stopping again, then plunging. Roseate is the most committed, just angling down and flying directly into the water.
ABOVE: Bill (culmen) length is shown at the top. Leg (tarsus) length is shown at the bottom.
ABOVE: Length of the longest tail feather, i.e. the streamer on the outermost rectrix.
ABOVE: Wing length, measured from the carpal bend to the tip of the longest primary.
ABOVE: Tern silhouettes. These are ‘classic’ examples – depending on posture, weather, temperature and moult, they may look quite different. For example, when they are sleeping or when it is cold terns tend to puff up their feathers more, making the legs disappear, and they hunch down, retracting the neck into the shoulders. Obivously tail streamer length would depend on the moult stage and amount of wear. Images traced from photos.
Arctic Tern is petite with a spikey bill and long wings and tail.
Antarctic is dumpy and quite heavyset; its tail may or may not extend beyond its wings.
Common is rather long-necked, with a smallish, elongated head and a forehead that slopes gradually into its bill.
Roseate has a very long tail but short wings; its bill is exceptionally long and usually clearly drooped.
ABOVE: I photographed these terns in early June on the West Coast. One could easily take the bird on the left for a Common Tern, judging by its flat crown, small-looking head and even a hint of a dark carpal patch. The one on the right look a lot bigger, with a larger, more rounded head and a dumpy shape – typical Antarctic. But…
ABOVE: Both are actually Antarctics in non-breeding plumage. When the left bird is a bit more relaxed now, its head once again looks bigger and assumes the typical round-crowned Antarctic shape. The white-speckled mid-crown would also be a good clue in this scenario. These sorts of variations need to be considered when evaluating shape.
Identification by plumage and bare parts colours
Plumage colour
These four species are essentially just variations on the same theme. In breeding plumage they have full black caps, reaching all the way down to the bill, and slightly darker underparts. In non-breeding plumage they develop white foreheads and whiter underparts. But there is an interesting footnote here. It is not clear that Antarctic Tern and Arctic Tern even assume non-breeding plumage at all! In their Antarctic range many moult directly from breeding into non-breeding and then straight back into breeding plumage in one continuous moult sequence. For the sake of consistency, I have labeled birds as non-breeding in this post. But in a big flock of Antarctics you’ll see a whole range of intermediates. In the case of Arctic, ‘full non-breeding plumage’ is seldom if ever seen in Southern Africa. Rather, the dull birds we see are more probably first-years.
One of the best ways to start getting a grip on terns, is by studying Common Tern in all its variations. The first thing you’re likely to notice is a very prominent carpal bar: a dark, horizontal band on the carpal region of the folded wing – i.e. the ‘shoulder’. This is present in immature and adult non-br. birds, but is even darker and more obvious in the former. A tern with a very bold blackish carpal bar is probably a Common. This bar may be shown by the other species too, but it is usually much less striking, being paler grey, less extensive and often obscured by the scapulars. In breeding plumage Common develops a faint, pale grey flush to the underparts – hardly even noticeable. But a few are a bit darker grey. On average, this is quite different to the deep grey of Arctic and especially Antarctic Tern. Just after arrival or just before departure (look at the clocks again), many terns would show a degree of breeding plumage. Roseate Tern develops a pink flush (that’s where its name comes from, but you have to use your imagination). In terms of overall colour, Roseate Tern is also notable for being very pale above and below – if you find yourself reaching for your sunglasses, it’s probably a Roseate. The others are light grey above.
Face pattern
This can be tricky because it is influenced by the stage of moult. In breeding plumage, Common and Roseate have slightly bigger white gaps between their black caps and gape lines compared to Antarctic and Arctic. The latter has a smaller black cap that does not extend so far back onto the nape as in Common. In non-breeding plumage, Common has a plain white forehead, rather sharply set off against the black rear half of the crown. The join between the black and white is more or less above the eye or even in front of the eye, and the border is often rounded or slopes slightly forward towards the bill, giving this species a distinct, contrasting white forehead patch. In Antarctic the white forehead is usually more extensive, angling back from the eye towards the nape. In addition, the white mid-crown is liberally speckled, and the black looks less solid, with a grey infusion and often blurry upper and lower borders.
Arctic is similar to Antarctic in non-breeding plumage, although its black cap tends to include its eye (about level with lower border of eye in the other three species). It also shows the backwards angle and the speckling though. Roseate is generally similar to Common Tern, but may have a smaller white forhead with some speckles. It also tends to have the black lower border extending straight back from the eye, while Common often has a dark blob extending down behind the eye like headphones. However, this varies a lot and depends on the angle of the head. Also, always keep in mind that moulting birds will have different and intermediate patterns. In all cases, also pay attention to bill shape and crown shape (see above).
…if you find yourself reaching for your sunglasses, it’s probably a Roseate.
ABOVE: Common Tern has a smaller, more defined white forehead patch, often with a rounded edge above the eye.
ABOVE: Antarctic Tern’s white forehead angles far back, almost to the nape, and is usually speckled.
Bill colour
Be careful to put too much emphasis on bill colour – many birders fall in this trap! Remember that bill colours in all species change, to a greater or lesser extent, from black in non-breeding to red or partly red in breeding. But this change does not occur overnight, and birds may show intermediate coloured bills for several weeks. Bill shape is often more informative than bill colour. But a few general remarks should prove useful. Common almost always has a black bill while in Southern Africa. Most (but not all) develop a red bill-base when breeding, and this may be seen just after and prior to migration. Note that the eastern race, longipennis, has a black bill even in breeding state. Arctic has a fully red bill when breeding and a black bill in non-breeding state. Roseate is quite interesting. Its bill is black most of the year, but develops a pinkish red or orangey base during the late egg incubation phase; this fades back to black after its chicks fledge. Antarctic is hard to classify. In autumn mixed flocks, about two thirds of the birds still have red bills. Many have black bills. And some have black bills with red bases. I wouldn’t rely too much on this – but a flock of red-billed birds, seen in winter, is most likely Antarctic.
Leg colour
Just like bill colour, leg colour is not particularly useful for identification in my opinion, but there are some clues. Roseate typically has orange instead of reddish legs (brownish when not breeding). Common Terns have bright red legs when breeding, but this fades to reddish brown when they are in Africa- the legs can look black in the bird’s own shade though. Ditto for Arctic. Lastly, Antarctic usually has red legs year-round (brighter when breeding though), but juveniles have dark legs that gradually become reddish.
ABOVE: This is a rather extreme example, but illustrates some of the points made above. Common Tern (top) has a solid black cap starting above the eye in a rounded curve and often black ear patches. It has a conspicuous dark carpal bar. Antarctic Tern (bottom) has a less neat black cap, which angles back from the eye and shows much speckling and diffuse edges. It lacks a carpal bar or has only a faint one (probably in younger birds). June, West Coast. Photos by Faansie Peacock.
Identification in flight
One of the most reliable ways to distinguish Antarctic and Common Terns in Southern Africa, is by the colour of the rump: white in Antarctic, Arctic and Roseate, and soft grey in Common. At certain angles or in strong light the rump can be a little tricky to see, but in general it is an easily observed and fairly obvious feature. The pale rump of Antarctic forms a blocky white patch that contrasts strongly with its back/scapulars, and meets the lower back in a straight line. Conversely, in Common Tern, the grey back bleeds onto the rump, forming a pale grey wedge that extends towards the tail. Note that the sides of the rump can be white though. Scroll back up to the big wallpaper image of all the terns in flight at the top of this page. Can you spot the Commons hiding among the Antarctics? I can count at least 8. Just for fun, can you find the hiding Swift Tern? One caveat is that Common Terns in full breeding plumage do show white rumps, but this plumage is only attained late in our summer, and many migrate back north before then.
What else can we see on the in-flight photos below? Let’s start with the upperwings. The Antarctic Tern pictured below is clearly in active wing moult, with the 5 outermost primaries (P10-P6) worn and still needing to be replaced; these darker feathers contrast with the plainer inner primaries (P5-P1; active moult centre between P5 and P6). The secondaries, i.e. the rear edge of the inner wing, look fresh; they are very pale grey and have wide white tips that form a broad white trailing edge to the wing. This bird seems to have just started moulting its central pair of tail feathers; the other rectrices seem worn, and the long streamers on the outer feathers are worn or broken off. The Common Tern has completed or nearly completed its moult, and looks uniformly fresh. Note its more conspicuous dark carpal bar on the leading edge of the arm. Also, its secondaries are darker than the Antarctic’s, forming a diffuse dark bar along the rear edge of the wing, with only narrow white tips. The fresh tail feathers are also notably darker than the Antarctic’s and have dark outer webs. Did you notice that the Common Tern is ringed on its right leg?
ABOVE: Antarctic Tern upperwing. White, square rump. Uniform pale grey primaries with broad white trailing edge. White tail. Photo by Faansie Peacock.
ABOVE: Common Tern upperwing. Diffuse grey wedge onto rump. Darker bar on secondaries with only a narrow white trailing edge. Darker tail. Photo by Faansie Peacock.
There are also clues on the underwing. Antarctic has very white underwings, with neat, narrow black fringes on the tips of its primaries. When the wing is fanned they look like neat black chevrons. When the wing is closed they line up to form a neat, narrow black line along the rear edge, quite like an Arctic Tern. Another feature shared with Arctic is that all of the primaries are translucent, forming a see-through bar along the rear wing when seen against strong light (not visible here). In Common Tern, only the inner primaries are translucent. Also, the undersides of Common’s primaries have broad but diffuse dark grey tips, forming a broad dark wedge or broad dark band along the rear edge, that becomes darker through wear.
ABOVE: Antarctic Tern underwing. Very white, with only narrow black fringes on outer primaries. This bird still has dark-edged streamers on its outer tail. Photo by Faansie Peacock.
ABOVE: Common Tern underwing. Broad, diffuse grey tips to primaries, forming broad trailing edge; darker secondary bar; narrow white trailing edge…and ring! Photo by Faansie Peacock.
ABOVE: This Antarctic Tern (white rump) has a fairly prominent dark carpal bar – it’s probably a first-year; the outer tail streamers are just beginning to grow. Photo by Faansie Peacock.
ABOVE: The tips of the primaries have neat, narrow black fringes in Antarctic Tern, creating a quite attractive pattern. Also note the very broad white trailing edge. Photo by Faansie Peacock.
ABOVE: You can see why Roseates are sometimes compared to ‘tiny tropicbirds’. This one is in fresh plumage, but the uppersides of the outer primaries become a bit darker with wear (though still have the broad white inner webs). Photo by Phil Penlington.
ABOVE: Roseate Terns have very white underwings, without an obvious dark trailing edge to the primaries. They look short-winged by long-tailed in flight (though wings foreshortened at this angle). Photo by Phil Penlington.
Juveniles and ageing
If you encounter an odd, heavily patterned creature with a short tail, lots of black bars and crescents, and often some orangey-brown tones, you’re looking at a juvenile, probably not more than 2-3 months old. This can be a very good clue, depending on the timing. Look at the breeding/moult wheels again. The two Northern Hemisphere breeders, Common and Arctic, breed in our (austral) winter. Common Terns gain their adult-like immature or “first-winter” plumage by Oct-Nov, shortly after they arrive here. A juvenile Common seen in our spring will look faded and washed out, and will have already replaced much of its juvenile plumage. Juvenile Arctic Terns moult a little later. They start moulting on migration, but only finish up in Antarctica. Even so, from about October, they will show only juvenile tertials and scapulars at most.
But if you see a very fresh juvenile, that has clearly left the nest only recently, it can only be a Roseate Tern or Antarctic Tern. The former breeds in our winter and spring, so fresh juveniles may be seen anytime between about August and December. There is thus a period of overlap with Common and Arctic, but those are likely to look much more worn, having traveled halfway across the world by the time they reach our shores. For recently fledged Rosies, it’s only a few wingbeats to the mainland from their natal colonies on Dyer Island and in Algoa Bay, so they will still look fresh and highly patterned. That being said, note that the gingery tones of young terns disappear very quickly, leaving only the black markings on a silvery background. Antarctic Terns breed in our summer on sub-Antarctic islands. By the time the birds start arriving on our shores in autumn, many are still in gorgeous juvenile plumage, as the pictures below demonstrate. Over the course of the next month or three their upperparts will gradually become greyer as more and more feathers are replaced. So a fresh juvenile in spring is most likely a Roseate. A fresh juvenile in autumn is undoubtedly an Antarctic.
ABOVE: Juvenile Antarctic Tern. Note the uniformly fresh primaries, with neat pale fringes. This is the only time in the bird’s life that the primaries will be all of the same age. Also note the distinct ginger colour patch on the lores. The bill is slightly shorter than in the adult, and will still grow for a few months. The tertials are heavily barred, and the wing coverts profuse marked. Young Roseates can look similar, but juvenile Arctic and Common Terns are much plainer. The latter has almost unpatterned grey wing coverts, and only only one large arrowhead on the tip of each tertial. They breed at different times of year though. Photo by Faansie Peacock.
ABOVE: The same juvenile Antarctic Tern (June, Jakobsbaai). With the head turned the ginger face has disappeared. The forehead is pale with speckles. In Roseates the forehead is often, but not always, darker. The bill is black, without any red, but the legs are dull reddish already. The tail is still short, without the prominent streamers of br. adults. Photo by Faansie Peacock.
ABOVE: In this slightly older juvenile Antarctic Tern (but same date as the ones above), the bill is already a smidge longer (compare to images above), and the plumage is a little more worn and faded, with very little orange-brown apparent. Also, this bird has just started replacing a few scapulars with grey adult-like immature feathers. Photo by Faansie Peacock.
ABOVE: This young Antarctic Tern would be termed a first-winter or immature. It has replaced most of its original juvenile wing coverts and scapulars with grey plumage. It is probably a bird that hatched quite early on in the breeding cycle. Perhaps populations on the different islands breed at slightly different times? Photo by Faansie Peacock.
Mid-tern exam
Okay, hopefully you won’t tern a blind eye next time you encounter these tricky birds. But let’s put those new-found skills to the test…
1Can you correctly age the four Antarctic Terns visible in this photo taken on 28 May on the West Coast?
Answer: Front and centre is an adult still in pretty much full breeding plumage, but starting its post-breeding body moult into non-breeding as evident by the mottled forehead. Directly behind is an adult in full non-breeding plumage. To the right is a juvenile moulting to immature plumage. And on the far left is a non-breeding type bird; its dark carpal bar may suggest that it is a first-winter immature. Photo by Faansie Peacock.
2What are these terns, and why?
Answer: They are all Roseates of course. They have orange legs, very long bills which droop quite clearly, ridiculously long tail streamers, and you can even make out the pink flush (by the way, that’s where their name comes from). Photo by Phil Penlington.
3Photos are not always sharp, and views are often fleeting. What bird is this? The tern, not the Crowned Cormorant!
Answer: It’s a Common. It has a dark bar along the secondaries, a prominent dark carpal region along the front edge of the wing, a solid-looking black cap, and short tail streamers. Blurry photo by Faansie Peacock.
4Without knowing when or where (in Southern Africa) this photograph was taken, what are the majority of these terns?
Answer: The key here is the presence of a fresh juvenile, only recently fledged. This limits the options to Roseate or Antarctic. The adult birds are nowhere white enough for Roseates, and have shorter and all-red bills in many cases. They are thus undoubtedly Antarctics. Faansie Peacock.
5What would this scruffy-looking little character be? Photographed at Strandfontein in Cape Town, 30 Dec, 2011.
Answer: Mmm…good question (why thank you, Faansie). I poached this off the simplybirding blog – check out the original post here. The photographer was ‘Francois’ but I am not sure who this is (not one of the Francois I checked) – if it’s your pic, please let me know and I can give credit where credit is due for this rather special sighting. This bird caused quite a bit of discussion. It is an Arctic Tern. Note the very short bill, extremely short legs, rounded crown, smallish dark cap including the eye, and rather extensive white forehead. The dark carpal bar may indicate an immature bird. It is in exceptionally worn plumage – the wing coverts have almost bleached to white, the black cap has turned brown, and the primaries are all but falling apart. This, and the fact that it was seen inland (though not too far from the sea), suggest that it may be a sick or injured bird. Photo by Francois.
6How many Common Terns can you see in the foreground?
Answer: Two. The one on the right sitting on the rock with the white crap on it, is a Common judging by its dark carpal bar and the colour and pattern of its black crown. But the bird spreading its wings is also a Common – see that faintly grey rump, which doesn’t contrast with the rest of the upperparts. The rest are Antarctics, including a nice juvie. Photo by Faansie Peacock.
7What’s going on here? May, South Africa.
Answer: Probably the best clue here is the narrow but sharply defined black edging under the primaries. This is typical of Antarctic or Arctic. Common would have a broader, diffuse grey edge along the rear of the wing. There are no tail streamers to speak of – a result of moult or wear, I would guess. The bill looks too long for Arctic and too short for Roseate. The underparts are clearly mottled grey. This is an Antarctic Tern in moult. Mottled grey and white underparts is actually quite typical of this species. Look carefully at all the Antarctic photos above again. Photo by Faansie Peacock.
8What species is this, and why?
Answer: Let’s see. Greyish underparts. Red patches here and there on bill, including the tip and an extensive white forehead that extends far back onto the mottled crown. That’s right – Antarctic Tern in non-breeding plumage.
Final words
What glorious birds terns are! The very image of grace and delicacy, yet able to travel 100,000 kilometres every year over the planet’s vast oceans. I am still terrified (tern-ified?) of them – but I certainly know a lot more about their identification then I did before I started writing this article. And they hold a special place in my heart, as I’m sure they do in yours. This post was originally intended as quick ‘photospot’ to publish some pictures of Antarctic Terns, but ended up being a full revision of tern identification in SA. Believe it or not, but it took only 97 drafts and around 48 hours of writing and photo editing, a lot of it post-midnight. Although a great deal has been written about the identification of terns, particularly in the Holarctic, there are still many questions that remain unanswered. If you have any comments, or if I’ve overlooked a good feature or over-emphasized a bad feature, I would love to hear from you! After all, one good tern deserves another.
PS: Sorry for all the bad puns.
ABOVE: My office for the day, with the bare essential office supplies: a scope, camera, binoculars, notebook and a flask of coffee. This is at the Jakobsbaai tern roost – a great site for Antarctic Terns from May to September. It is advisable to go at high tide, when there are fewer rocks for the birds to perch on. They are then closer to the beach, and sometimes on the beach. Just be careful not to push it too far and disturb these birds – now classified as Endangered because of the small breeding population on SA’s Prince Edward islands. There are always Swift, Sandwich and Common Terns around too, and occasionally Roseates.
ABOVE: Looking over the tern roost at Jakobsbaai (Mauritzbaai), with some of the typical West Coast architecture of this picturesque village visible in the background. If you’re ever looking for a peaceful “huisie by die see” – look no further.
Finding Antarctics
There are a number of established traditional winter roosts for Antarctic Terns (and other species) dotted around our coastline. I live in Langebaan, so the most convenient one for me is the roost at Jakobsbaai (Jacobs Bay) between Vredenburg and Paternoster. Park here: -32.977264, 17.886627. There are often roosting terns just north of Tsaarsbank in West Coast National Park too: -33.146004, 17.996357. Another West Coast stakeout is on the rocks south of Paternoster, towards Columbine NR and Tietiesbaai; try anywhere south of here: -32.817235, 17.865797. Otherwise, Kommetjie on the Cape Peninsula can be good, or Cape Recife in the Eastern Cape. You could also try Danger Point south of Gansbaai, which often has Roseate Terns too. Terns roosts are generally best at high tide. Common Terns live up to their name, but Arctic Terns are very few and far between. You probably have a better chance of encounter this passage migrant on pelagic trips in spring and autumn.
Please keep in mind that the tern roosts are very sensitive to disturbance. The birds are usually relaxed given a slow approach. But please don’t go any closer if the birds start becoming alarmed at your presence. These birds are recuperating, resting and digesting their food after a hard migration or long hours of fishing out at sea – give them a break!
ABOVE: Preening is serious business! The terns devote a large proportion of their time to keeping their plumage in good shape while they’re perched. Each feather is meticulously and thoroughly worked over with the bill, often resulting in some loose downy fluff sticking to the salt-encrusted bill (usually along the ridge below the nostril, where the excess salt that is excreted from the supraorbital salt glad, drains out of the nostril). Anyways, preening birds provide good opportunities to get a look at the wing and tail feathers and the rump, as the bird contorts its body into all sorts of weird positions to get hold of those hard-to-reach feathers. From top left: Preening lesser wing coverts; rubbing crown against wing-edge; with a mouthful of secondaries; manipulating an outer tail streamer; working on an outer primary (x2). Photos by Faansie Peacock.
If you found this post useful, you’ll love my books on LBJs and Waders. Both still available.
BELOW: Kerguelen Tern illustration by Faansie Peacock. From the 2015 Eskom Red Data Book of Birds of South Africa, Lesotho and Swazland.
An interesting post on a moulting juvenile Antarctic from Madagascar – could this be the northernmost record? And in the Indian Ocean nogal.
http://birdingfrontiers.com/2014/01/17/antarctic-tern/
what struck me the first time I saw Antarctic Terns (also in Jacobsbaai) was that the jizz of birds in flight looked more like marsh terns than sea terns.
Very true Karel – they do have something of a marsh tern about them (especially a Whiskered). Thanks for the comment!
Faansie
This short blog terned into something spectacular… thanks for the insights.
Kommetjie – For several years now, terns, particularly Antarctics do not seem to roost hrere anymore.
Possibly too much human and dog distrubance?
Other numbers of terns also reduced.
Many years ago it used to ‘the’ tern roost on the peninsula.
Hi Mel
Thanks for the message and the pun. That is sad news about Kommetjie. I wonder if the birds have found a new, more secluded spot somewhere on the Peninsula?
Hi Faansie
This is so interesting! Terns are really amazing.
Is this information captured in any of your books?
Have just bought my copy of Waders 😊
Kind regards
Michelle
Hi Michelle. No books specifically on terns, but you can download my app “Firefinch” for iOS and Android. The first chapter on seabirds is free and includes all the terns. F