Super Saturday ID CHALLENGE 18 July 2020: by Pamela Keil
Tern, tern, tern — for every tern there is a season…
It’s the terns turn for an ID super challenge. These tern photos were taken from all around the country by several of the admins — mine are the blurry ones. A warning — some of these may or may not be the same species… Take each one on its own merits.
L-Platers: There are a few that you might be able to get to species, or try to narrow them down to a few choices.
P-Platers: Try to ID them all, or narrow them down to two possibilities with your reasoning.
Advanced: If you know one easily, just smile… But for any you have to look up, give your best ID for species, breeding/non-breeding, and age — and explain how you got there.
If you’re struggling or don’t know where to start, BirdLife has created a handy tern guide: http://birdlife.org.au/documents/MyTern-v7.pdf
Information for each photo:
- Phillip Island, VIC in February 2014
- Cairns, QLD in July 2009.
- Taken by Karen Weil at Western Treatment Plant VIC
- Wollongong, NSW in April 2019
5. Taken by Sonja Ross at Lord Howe Island in April
6. Alice Springs Sewage Ponds, NT in December 2013
7. Taken by Karen Dick on an Eaglehawk Pelagic, TAS in September
8. Alice Springs Sewage Ponds, NT in December 2013
9. Phillip Island, VIC in February 2014
10. Cairns, QLD in July 2009
11. Taken by Karen Dick on an Eaglehawk Pelagic, TASin May
12. Alice Springs Sewage Ponds, NT in December 2013
13. Taken by Karen Dick – at sea off the NW coast (of Australia)
14. Alice Springs Sewage Ponds, NT in December 2013
Added note: all the terns taken at the Alice Springs Sewage Ponds in December 2013 were hanging out together. The photos were all taken in the same area over the course of a few hours.
Solution:
Some generic tips for helping to ID terns.
One of the key things to remember about the terns is that most species have several different plumages, and of course a bird may be between moults and have some combination of different plumages. So, like with many other species, the best thing to do is to ignore the plumage to start.
Before you look at plumage characteristics, look at the overall shape of the bird, including wing and tail shape, and especially bill thickness and length. Bill colour and leg colour can also help, but note that many of the terns have a breeding flush that changes the bill colour. Red, yellow, or orange bills can help you narrow down the species, but do not depend on this as your only ID character.
Once you’ve narrowed it down to a few species, the key plumage characteristics include the extent and shape of the black cap. Juvenile birds often have brown feathers speckled through the grey, and often have a more extensive dark cap than the non-breeding adults of the same species. Breeding plumage birds tend to be a little bit easier to tell apart, and often have the blackest & most solid cap of all the plumage variations.Also — terns are hard! So don’t worry if you’re having trouble with your IDs!
ID — TERN #1
This is a Caspian Tern.
Key ID feature: Very large tern, with a large, thick red bill. If you see a thick red bill like this, then check the other ID features to see if they match.
Other ID features: From this angle it’s difficult to tell, but the cap is relatively solid looking and goes down to the bill, suggesting that this bird is in breeding plumage or close to it. The black base to the primary feathers is also diagnostic of Caspian Tern.
ID — TERN #2
This is a non-breeding Australian (Gull-billed) Tern.
The Gull-billed Terns have recently been split, with two species possible in Australia: the Common Gull-billed Tern (formerly ssp affinis) which is found occasionally on the Northwestern coast and the more commonly found Australian Tern (formerly ssp. macrotarsa), which can be found in most costal areas, and even inland at water sources.
Key ID feature: Relatively big, though not as big as Caspian, with a very large, thick black bill. Additional ID features: By the dark eye mask and mottled black cap that extends to the bill, we can tell that tern is in non-breeding plumage and this also confirms that this is an Australian Tern rather than the Common Gull-billed Tern.
ID — TERN #3
This is a White-winged (Black) Tern in partial breeding plumage.
Key ID feature: When you see distinctive plumage like this, you can use plumage as an ID feature. The only terns with this extensive black are the White-winged Black or the vagrant Black Tern. In this photo, you can see the white tail and rump, and the white wing, which make this a White-winged Black rather than a Black Tern.
But also note the small bill and reddish legs, as these are important for ID when the birds are in non-breeding plumage.
ID — TERN #4
This is an Adult (greater) Crested Tern in breeding plumage.
Often called just a Crested Tern, but people often tell add the “greater” to distinguish it from the Lesser Crested Tern.
Key ID feature: The long, pale yellow bill is the key characteristic for IDing this tern. The bill is yellow for its full length, and does not have a dark tip as in some other species. These are also a relatively large tern.They do have a crest as adults, but can lower it so it’s not visible. Don’t depend on the crest as a key ID feature, but keep an eye on it. Lesser Crested Terns look similar, but their bill is more orange than yellow. Distribution can help narrow it down between the two, as the Lesser Crested Tern is not found along the southern coasts. In breeding plumage, the black cap of the Lesser Crested Tern extends to the base of the bill, while the Crested Tern has a white frontal band (as seen in this bird). The solid black cap indicates that this bird is in breeding plumage.
ID — TERN #5
These are three adult Sooty Terns.
Key ID feature: The deeply forked tail and bicolour wing from below narrow this down to two terns: Bridled or Sooty. Both also have a black line running from the cap through the eye to the base of the bill.
To distinguish between the two species: Bridled’s white frontal patch extends in a point behind the eye, while Sooty have a white patch that stops before the back of the eye. The Bridled tern also has white bases to the primaries, whereas the Sooty has primaries that are dark to the base (although the coverts are white).
From this angle, it is difficult to tell if these birds are in breeding or non-breeding plumage. In breeding plumage, their backs are dark black, with paler fringes showing in non-breeding plumage.
ID — TERN #6
This is an adult Whiskered Tern in breeding plumage.
Key ID feature: The dark grey belly and red bill and legs are diagnostic for breeding Whiskered Terns. They are a medium sized tern, and common at inland water sources.
I’ve even found Whiskered Terns chasing termites in the Tanami after a heavy rainfall caused overland flooding.
ID — TERN #7
This is an Antarctic Tern in non-breeding plumage… which I’ll let Karen explain.
From Karen Dick:
The structure is Antarctic because of the relatively deep-based, slightly droopy bill, the boofy head with steep forehead, and the rotund body. The relatively uniform grey back and upperwings, contrasting with a clean white rump, the presence of moderate translucency in the remiges and the diffuse but obvious dusky trailing edge to the outer 6 or so primaries are the Antarctic features in the plumage.
Arctic Tern would typically appear slightly less rotund and less full bodied with a narrower and straighter bill. The dark trailing edge to the underwing would be narrower, more blackish and appear more neatly defined especially on the inner primaries. This narrow black trailing edge of Arctic Tern would also be expected to extend further than in Antarctic Tern. Also, the relatively broad and uniform dark strip on the inner web of p10 and p9 (next to the feather shaft) is too broad for Arctic Tern. An Arctic Tern would also be expected to show obvious translucency across all remiges when viewed from below whereas the Eaglehawk Neck bird shows moderate translucency across the remiges with this feature being most pronounced on the inner primaries”
ID — TERN #8
This is a young White-winged (Black) Tern, probably moulting from juvenile to immature non-breeding plumage.
Key ID feature: These birds look like they’re wearing black earmuffs like a fighter pilot. The muffs get narrower in adult birds.
Be careful to distinguish between the White-winged and non-breeding/young Whiskered Terns. The white rump can help in this diagnosis. Also, the ear muffs are more pronounced, curving around the eye. Whiskered Terns have a band that extends backwards toward the nape rather than up over the eyes, except in juveniles. As adults, the cap of Whiskered Terns is much fuller and no longer resembles earmuffs.
The two species often hang out together, especially inland. When you see them together, the White-winged are noticeably smaller than the Whiskered, though both would be considered medium-sized terns.
ID — TERN #9
This is a juvenile Crested Tern.
Key ID feature: The pale yellow bill is characteristic of this species, but be careful as the bill is shorter in juveniles. In other yellow-billed species, the bright yellow bill is slightly more orangey, and often has a dark tip. When out of breeding plumage, the bills become darker. A clean pale yellow bill is the best ID feature to pick Crested Tern.
The mottled plumage and dark head tell us that this is a juvenile bird.
Another tern that can cause some confusion is tern #9. Mainly because the bill seems shorter than you would expect. This photo by Karen Dick shows adult and juvenile Crested Terns together, and you can see that the juveniles have a shorter bill than the adults. Photo from Tasmania in December.
ID — TERN #10
This is an adult Australian (Gull-billed) Tern in breeding plumage.
Key ID feature: Relatively big, though not as big as Caspian, with a very large, thick black bill.
(See Tern #2 for more ID features.)
ID — TERN #11
This is a juvenile White-fronted Tern.
The dark black bill, heavily scalloped back, and dark cap with only a small frontal band suggest that this is a juvenile of one of three potential species: Black-naped, Roseate, or White-fronted Tern.
And we can narrow it down further by location — this bird was seen out to sea on a pelagic from Eaglehawk Neck (Tasmania). Making the most likely candidate White-fronted Tern.
There are additional small points that can help confirm this ID, such as the extent of dark plumage on the wing coverts and the heft of the bill.
ID — TERN #12
This is a non-breeding adult Whiskered Tern.
Note that in non-breeding plumage, Whiskered Tern no longer have the easy diagnostic features of red legs and bill or the grey belly. Look for the streaked cap that extends down the nape without making “earmuffs”.
Location at an inland site is also helpful in ID for this species, as many of the terns are only found right along the coast or further out at sea.
ID — TERN #13
This is a Sooty Tern. (See also Tern #5)
Key ID feature: The deeply forked tail and bicolour wing from below narrow this down to two terns: Bridled or Sooty. Both also have a black line running from the cap through the eye to the base of the bill.
To distinguish between the two species: Bridled’s white frontal patch extends in a point behind the eye, while Sooty have a white patch that stops before the back of the eye. The Bridled tern also has white bases to the primaries, whereas the Sooty has primaries that are dark to the base (although the coverts are white).
From this angle, it is difficult to tell if these birds are in breeding or non-breeding plumage. In breeding plumage, their backs are dark black, with paler fringes showing in non-breeding plumage.
ID — TERN #14
I had this as a juvenile Whiskered Tern.
Note that this bird has what looks a little like the earmuffs of the White-winged Black Terns, but the dark patch is larger and extends back down the nape. You can also see a bit of grey/brown on the rump rather than the white of the White-winged Black. However, as Sonja pointed out, there is some white on the sides of the rump. So I am happy to discuss this one further… The mottled feathers tell you that it’s a juvenile.
A few of the comments left by you lovely ladies had me questioning my ID for Tern #14 — so I’m adding another photo of the same bird. This is Tern #14 from a different angle.
Please discuss in the replies to this photo if you have any opinions on whether this is a juvenile White-winged (Black) or juvenile Whiskered Tern. 🙂
You can see that the rump is silvery, but the wings are dark rim and the back is not distinctly scalloped. There also seems to be a little white just behind the cap before the back. So despite the lack of white on the rump, this may be a juvenile White-winged Black Tern.
I’m happy for any discussion on this bird. Or it may have to go into our “mystery tern” folder… 🙂
Women Birders Australia 