Adult ‘American Black Tern’ summering in Northumberland

Abstract An adult Black Tern Chlidonias niger, initially identified as a ‘European Black Tern’ C. n. niger, was present at a tern colony at Long Nanny, Northumberland, during the summers of 2020 and 2021. At the end of summer 2021, the bird was reidentified as an ‘American Black Tern’ C. n. surinamensis – the first record of a breeding-plumaged adult in Britain. The bird returned again in summer 2022. This paper discusses the bird’s occurrence, its identification and other records of American Black Terns in breeding plumage in Europe.

Introduction
A Black Tern Chlidonias niger was discovered on 30th May 2020 at the Arctic Sterna paradisaea and Little Tern Sternula albifrons colony at Long Nanny, Northumberland. The bird was regularly seen visiting the tern colony during summer 2020, the last definite sighting being on 25th June. The bird returned in 2021, when it was seen between 19th May and 22nd July, and again in 2022, when it was recorded between 13th May and 29th August. As the bird could often be observed at close range, it proved popular amongst local and visiting birders, and many good photographs were taken (e.g. plates 107 & 108). 

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107. ‘American Black Tern’ Chlidonias niger surinamensis, Long Nanny, Northumberland, June 2020. The bird regularly brought fish into the tern colony and used the fish to display to Arctic Terns Sterna paradisaea. 

Andrew Jarwick

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108. American Black Tern, Long Nanny, June 2021. The black underparts combined with the noticeable white leading edge along the wings create an appearance reminiscent of White-winged Black Tern C. leucopterus.

Frank Golding

During summer 2021, I was undertaking survey work to look at disturbance of birds by recreational activities at Lindisfarne NNR. A colony of Arctic and Little Terns on Black Law fell within the area I was surveying, being viewable from Holy Island and Ross. On 10th July, I was surprised to pick out a breeding-plumaged adult Black Tern roosting on intertidal rocks near this colony. I realised it was likely to be the Black Tern that had been seen at the Long Nanny tern colony. I made a note to check the features of ‘American Black Tern’ C. n. surinamensis after I had returned home from the survey work, motivated by a long-held ambition to find a rare tern in a Northumberland tern colony and a desire to learn what adult American Black Terns looked like in breeding plumage.

As I checked the first few online photos of adult American Black Terns, I was amazed at their similarity to the Northumberland bird. In particular, the striking black underparts of the Northumberland individual matched those of American Black Terns, clearly darker than those of ‘European Black Terns’ C. n. niger. It also quickly became apparent that American Black Terns have darker upperparts than European birds, and this feature was also shown by the Northumberland bird. 

I soon learnt of further features for separating American from European birds: American Black Tern shows whiter underwings and a paler leading edge along the wings compared with European Black Tern (Harrison et al. 2021; plate 109). Combined with the darker underparts, the overall look of American Black Tern can therefore be reminiscent of White-winged Black Tern C. leucopterus. 

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109. American Black Tern, Long Nanny, June 2022. The bird’s underwings frequently appeared silvery-white, whereas European Black Tern C. n. niger often shows darker underwings. However, their apparent shade varies with light conditions.

Jonathan Farooqi

I e-mailed photos of the Northumberland bird to various people with relevant experience of American Black Tern. The majority of responses were in favour of American, while the remaining people replied that they had no experience of separating adult American from European. 

Klaus Malling Olsen commented: ‘[The Northumberland bird] is as good as it gets for surinamensis. The head and underbody are concolorous (in niger, the head is usually the darkest part, slightly contrasting against the greyer-tinged body), the underwings really look white, the upperparts are slightly darker than in niger, and T6 [the outermost tail feather] is as grey as the rest of the tail (in niger, this is slightly paler).’

Following the bird’s reidentification as an American Black Tern in late July 2021, the news was put out on national bird-news services. However, few people saw the bird in 2021 following its reidentification; it was not seen again that year after 22nd July.

The bird returned once again in 2022 and, this time, many more birders had a chance to see it.

After checking through past records on BirdGuides (www.birdguides.com), it became clear that the bird had also been present at other locations in Northumberland. On 30th June 2021, it was at East Chevington, while sightings of a ‘Black Tern’ at various sites along the Northumberland coast during the summers of 2020 and 2021 may also have related to the same individual. In summer 2022, the bird was also seen on the Farne Islands and Coquet Island. 

It was suggested that the bird could have been the juvenile American Black Tern seen briefly at St Mary’s Island, Northumberland, on 7th October 2019 (the first county record; Brit. Birds 113: 608–609). However, since Black Terns – both American and European – show a distinct first-summer plumage, it would have been expected that the Long Nanny bird would have exhibited such a plumage in summer 2020. That it didn’t – it was in full adult breeding plumage – shows that it was a different (older) individual. 

The adult American Black Tern was seen bringing fish into the Long Nanny tern colony in 2020 and 2021 (plate 107), and conversations with the National Trust tern wardens on site revealed that it was regularly seen displaying to Arctic Terns in 2022, even into June, when Arctic Terns already had eggs. This behaviour indicated that the bird was a male. Perhaps not surprisingly, it has so far been unsuccessful in attracting a mate.

In certain lights, the bird’s head appears slightly darker than the underparts, which further supports it being a male, as males are reported to have darker heads than females (Andrews et al. 2006).

Identification
In 1999, the time of the first British record of American Black Tern, Andrews et al. (1999) commented that it was difficult to find any detailed references on surinamensis other than Olsen & Larsson (1995). Since then, a number of publications (McGeehan 2000; Hallam & Lewington 2009; Harrison et al. 2021) and a series of British records have helped to make the identification of juvenile American Black Tern well known amongst birders. However, the separation of adults in breeding plumage has been less well documented, likely as a consequence of the lack of records of adult American Black Terns in Europe.

Compared to European Black Terns, American Black Terns show: darker underparts; darker upperparts; paler underwings; a more obvious pale leading edge to the wings; and black bleeding down from the back of the neck onto the mantle (see also fig. 1 and plates 110 & 111). 

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Fig. 1. Upper: ‘American Black Tern’ Chlidonias niger surinamensis, Long Nanny, Northumberland, June 2020, Tom Tams; inset: Gary Woodburn. Lower: ‘European Black Tern’ C. n. niger, Farmoor Reservoir, Oxfordshire, April 2016, Roger Wyatt; inset: Josh Jones.

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110. European Black Tern, Dernford Farm Reservoir, Cambridgeshire, May 2022; and 111. American Black Tern, Long Nanny, June 2022. As described in Olsen & Larsson (1995), the black of the head of American Black Tern extends down onto the mantle, but there is a better-defined transition between the black head and grey mantle in European Black Tern. As in juveniles, the rump and uppertail-coverts are darker on American Black Tern than on European Black Tern.

Daniel J. Field

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Jonathan Farooqi

Klaus Malling Olsen (pers. comm.) suggested that American and European Black Terns differ in the coloration of their outer tail feather: in American, T6 (the outermost tail feather) is a similar shade of grey to the rest of the tail, whereas in European, T6 is slightly paler. The Northumberland bird showed an outer tail feather that was equally as dark as the rest of the tail, which suggested American. To test the usefulness of this feature, I examinded 50 photos of each taxon and categorised the colour of T6 as either the same as or paler than the rest of the tail. I found only a small difference between European Black Terns (14% showed a paler outer tail feather) and American Black Terns (2% showed a paler outer tail feather). Furthermore, whether or not the outer tail feather was actually paler than the rest of the tail was debatable in some images of some individuals.

Using the same photos, I also looked at the coloration of the outer web of T6. Again, I found little difference between European (28% showed a paler outer web, 72% showed an outer web the same colour as the rest of the feather) and American (22% showed a paler outer web, 78% showed an outer web the same colour as the rest of the feather). Overall, I found the coloration of the outer tail feather of little use in separating individual American Black Terns from European Black Terns.

Andrews et al. (2006) suggested that American Black Tern has a bright vermilion-coloured gape, whereas European Black Tern has a pinkish-red gape. However, the ability of Andrews et al. to test this feature was thwarted by a lack of available photos. Since then, a greater number of photos has become accessible, particularly in Cornell Lab of Ornithology’s Macaulay Library (www.macaulaylibrary.org) and the BirdGuides photo gallery. I checked 31 photos of adult American Black Terns and 22 of adult European Black Terns where the gape was visible. I categorised 55% of American as showing a pinkish-red gape and 45% a bright,vermilion gape, and 23% of European as showing a pinkish-red gape and 77% a bright vermilion gape. I also checked whether a difference in gape coloration might be apparent only in the breeding season. To test this, I checked the gape coloration of American and European Black Terns photographed between April and June. In 18 photos of American and 17 of European, there was little change in the percentage of birds showing a pinkish-red or vermilion gape (in American, 56% were pinkish-red and 44% were vermillion; in European, 24% were pinkish-red and 76% were vermillion). My analysis therefore suggested that there is much overlap in the apparent gape coloration between American and European Black Terns. Assessing gape coloration can also be subjective, being influenced by light conditions and angle/distance of the bird, and any differences in coloration are likely to be slight. Furthermore, assessing gape coloration is possible only when Black Terns are at close range and have their bills open. Overall, I did not find gape coloration to be useful in separating American and European Black Terns.

Andrews et al. (2006) also stated that the American Black Tern has a later moult into non-breeding plumage than European birds. In American birds, the moult starts from mid June, with many still in breeding plumage in September, while in European Black Tern, moult starts in late May and many birds are in non-breeding plumage by the end of September. In both 2021 and 2022, the Northumberland bird commenced its moult into non-breeding plumage (as evidenced by white, non-breeding feathers appearing around its face) in the first week of July, in line with the expected moult timing of American Black Terns. In late August 2022, the bird was found at Budle Bay (12 km north of Long Nanny) and was still predominantly in breeding plumage when it was last seen there, on 29th August. Interestingly, its state of moult was unchanged from when it was last seen at Long Nanny one month previously in late July (see plate 112). This may represent a suspension of the bird’s moult, as American Black Tern is known to begin its moult on its breeding grounds and complete it on its wintering grounds (Heath et al. 2020)

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112. American Black Tern, Long Nanny, July 2022. This photo was taken on 13th July and the white around the bill indicates that the bird is beginning its body moult into non-breeding plumage. Many American Black Terns begin moult into non-breeding plumage three to four weeks later than European Black Terns. The Northumberland bird’s state of moult when seen at Budle Bay in late August 2022 was unchanged from when it was last seen at Long Nanny one month previously, in late July, indicating that the bird had suspended its moult once it left Long Nanny.

Richard Tyler

To test the extent to which moult timing could be used to distinguish American and European Black Terns, I checked for photos on the Macaulay Library website of birds beginning to show the first signs of moult into non-breeding plumage (i.e. a small number of white feathers around the bill). I found photos of 65 American and 51 European birds fitting the criterion. The mean date on which the 65 American birds were showing the first signs of moult into winter plumage was 31st July (s.e. ±2.31 days), while the mean date for the 51 European birds was 2nd July (s.e. ±2.52 days). The earliest date on which an American Black Tern showed signs of moult was 3rd July, in contrast to 1st June in European Black Tern. These dates are later than those reported by Andrews et al., but my dates are based on a fairly small sample, plus it is likely that some birds had started moult before the photo was taken. In summary, moult can be useful in separating American and European Black Terns – any Black Tern still in full breeding plumage or showing only the first signs of moult after late June should be checked for American Black Tern.

Andrews et al. (2006) stated that American Black Terns show a scattering of white feathers around the face at the beginning of body moult, whereas white feathering is limited to the rear lores, throat and area below the eye during the early stages of body moult in European birds. The Northumberland bird showed a scattering of white feathers around the bill at the beginning of its moult, which aligned with the pattern Andrews et al. suggested was shown by American birds. To test the usefulness of the pattern of white feathers around the face at the beginning of moult, I checked photos in the Macaulay Library of 59 American and 46 European Black Terns that were beginning to show some newly moulted white feathers around the face. Most (95%) American birds showed an even scatter of newly moulted white feathers around the face (table 1). The pattern of white feathers on the face of European birds was more variable: 61% in my sample showed an even scatter of newly moulted white feathers around the face, while the remaining 39% showed white feathers limited to the throat, lores and below the eyes. My research indicated that a scattering of white feathers around the face of an adult Black Tern would support the identification as American but would not in itself rule out European, while newly moulted white feathers limited to the throat and under the eye would be more suggestive of European. It is possible that European birds show white feathering limited to the throat, lores and below the eyes only at the beginning of moult and this may not be applicable to any individuals that are more than about two weeks into their moult from breeding to non-breeding plumage. 

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Fig. 2. Top left: European Black Tern, Grau de Piémanson Provence-Alpes-Côte-d’Azur, France, July 2018. Thomas Galewski Top right: European Black Tern, Pays-de-la-Loire, France, July 2013. Frantz Delcroix Bottom left: American Black Tern, McCurtain, Oklahoma, USA, July 2012. Brian Davis Bottom right: American Black Tern, Chippewa, Michigan, United States, July 2021. Sue Kurtz. Most American Black Terns show an even scattering of white feathers around the face (bottom left), although many European birds also show this feature (top left). Conversely, while newly moulted white feathers limited to rear lores, throat and area below the eye would be more suggestive of European Black Tern (top right), a similar pattern can be shown by a small percentage of American birds (bottom right).

Harrison et al. (2021) commented that adult American Black Terns show an even scatter of white feathers across the head and underbody during their moult into non-breeding plumage, whereas European Black Terns moult the head first before moulting the underbody. I checked photos of 166 European birds and 196 American birds (all adults) that were moulting into non-breeding plumage. I categorised birds based on the extent of moult: (1) head only, (2) primarily head but some body, (3) head finished, body in moult and (4) similar extent of moult across body and head. While I found that American Black Tern showed an even scattering of white feathers across its head and underbody (category 4) more often than any other pattern (categories 1–3), it was clear that stating American Black Tern shows this pattern whereas European does not is over-simplistic (see fig. 3). Indeed, 62% of American Black Terns were categorised as category 1–3. In addition, 7% of European Black Terns showed an even scatter of white feathers across the head and underbody. I therefore concluded that the extent of white feathers of the head and underbody is only of limited usefulness in separating European and American birds. The pattern of moult is likely to be influenced by moult stage – although most or all American Black Terns may go through a phase of showing an even scatter of white feathers, many birds show white feathers limited to the head at the beginning of moult, or head moult may be finished whilst the underbody is still moulting towards the end of moult.

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Fig. 3. Comparison of the extent of moult into non-breeding plumage in American Black Tern and Euro-pean Black Tern. Photos of 166 moulting European birds and 196 moulting American birds were divided into four categories based on extent of moult (see text). The graph shows that American Black Terns in my sample more frequently showed a similar extent of moult across the head and body than other patterns, but this pattern was the least common in European Black Terns. Top row, l–r: Frantz Delcroix, Pavel Štěpánek, Christoph Moning, David Lindo. Bottom row, l–r: Brian Davis, Jay McGowan, Rick Bowers, Brian Sullivan.

The coloration of the crown is a useful feature in separating adult American and European Black Terns that are moulting to non-breeding plumage. In American Black Tern, the crown appears to be grey, whereas in European Black Tern the crown appears to be more solidly blackish (Rich Andrews pers. comm.). This difference in apparent darkness may be caused by a difference in the amount of white mottling in the crown – American Black Tern shows more than European Black Tern. This difference in crown coloration will become apparent as moult of the head nears completion in summer.

Accurately gauging the darkness of the underparts and upperparts is key in the identification of adult American Black Terns. However, light conditions can greatly influence the apparent coloration of the plumage, to the extent that the difference in coloration between photographs of the same individual can appear as great as the difference between subspecies (see plate 113). When foraging, for example, Black Terns are constantly changing their posture and angle relative to sunlight, with different feather tracts shaded and exposed to sunlight in any given moment, which creates a changeable impression of coloration. Assessing coloration of Black Terns is likely to be most straightforward in flat light with high and light cloud cover. In dull and overcast conditions, European Black Terns can look darker, while in strong sunlight American Black Terns can appear paler. In Britain, adult breeding-plumaged Black Terns are often observed in spring in poor weather conditions (dull and overcast with precipitation) when they are forced down to inland waterbodies during their cross-country migration.

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113. American Black Tern, Long Nanny, June 2021. The underparts appear paler here, which is likely to be due to a combination of light conditions, camera settings and post-processing of the image.

Frank Golding

The coloration of the surface beneath the bird is also a factor – the underwings of an adult Black Tern will appear paler when the bird is above sand than when it is above water. When checking photographs, an assessment of coloration should be made using a series of photographs rather than just one or two. This is because, in a single photograph, American Black Tern can look pale and European Black Tern can look dark, depending on light conditions and camera settings.

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Fig. 4. Top (left to right): American Black Tern, Long Nanny, Northumberland, May 2022, Chris Cummings; July 2022, Eric Barnes; May 2022, Chris Cummings. Middle (left to right): American Black Tern, Idaho, USA, May 2022, Tom Baumgart; Michigan, USA, May 2022, Ben Lucking; Wisconsin, USA, June 2010, Geoffrey Hill. Bottom (left to right): European Black Tern, St Aidan’s RSPB, West Yorkshire, May 2019, Nathaniel Dargue – although this bird shows a white leading edge to the wing, it is relatively thin and does not reach as far as the bird’s alula; Cranmere, Shropshire, May 2019, Richard Moores; Farmoor Reservoir, Oxfordshire, April 2015, Roger Wyatt.

Vocal differences appear to exist between American Black Tern and European Black Tern (Magnus Robb in litt.). The main advertising call of American birds (e.g. https://xeno-canto.org/160707) appears to be much faster than that of European birds (e.g. https://xeno-canto.org/102222). This apparent difference in vocalisations may be limited to adults. However, differences in vocalisations between surinamensis and niger need to be properly tested using an appropriate sample. I could find no recordings of the Northumberland bird.

The behaviour of the Northumberland American Black Tern – returning in multiple years to spend the summer in a coastal Arctic and Little Tern colony – is unusual in Britain. American Black Tern breeds in shallow freshwater marshes in open and forested country (Heath et al. 2020) and European Black Tern breeds ‘mainly in well-watered lowlands but locally at mountain lakes up to 2,000 m’ (Cramp 1985). Only during the non-breeding season does Black Tern tend to use marine and coastal habitats. I searched the BirdGuides sightings database for long-staying Black Terns in Britain in June and July; this indicated that long-staying summering birds are unusual, though there are some examples. An adult was present at St Aidan’s RSPB, Yorkshire, between 27th May and 8th August 2017, and what was presumably the same bird returned the following summer between 6th June and 18th August 2018 and again in 2019. A first-summer was present at Rutland Water, Leicestershire & Rutland, between 14th June and 26th August 2021. Photos confirm that both of these individuals were European Black Terns. Both were at inland wetland sites where Black Terns are typically found on migration; I was unable to find any long-staying birds during the summer at coastal tern colonies. It is interesting to speculate whether the Northumberland bird’s behaviour is useful in an identification context: is this behaviour – summering at a coastal tern colony – more prone to occur in American Black Tern? Or is the Northumberland bird’s behaviour unrelated to its subspecies and instead related to the fact it is a vagrant in an unfamiliar context? Possible support for the former was provided by Nisbet et al. (2013), who reported that, in several years since 1995, one or two pairs of American Black Terns have nested on three islands in the Gulf of Maine, USA, and one in the Bay of Fundy, Canada. Eggs were laid in at least five cases and a chick hatched in at least one case, but no chicks were raised to fledging. While undertaking fieldwork at a Common Tern S. hirundo colony at Bird Island, Massachusetts, USA, Ian Nisbet (pers. comm.) recorded up to three American Black Terns around the island on most days in late May and June. These were mostly first-summers but included a few subadults and one or two adults in full breeding plumage in most years. In addition, a pair of American Black Terns nested in a coastal Common Tern colony in New Brunswick, Canada, in 2004 (Craik et al. 2006). 

I searched the databases of photos on the BirdGuides and Macaulay Library websites for possible adult American Black Terns that have been misidentified as adult European Black Terns. The search did not find any good Americancandidates; however, it showed how individuals of European birds can occasionally look as dark as American birds in some images while appearing normal in others (plates 114 & 115).

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114 & 115. European Black Tern, Dernford Farm Reservoir, Cambridgeshire, May 2022. These photo-graphs show the same individual on the same day; they demonstrate how European Black Terns can appear darker than expected in one photo but as expected in another photo. Light, camera settings and photo post-processing all influence the apparent darkness of Black Terns.

Rachel Lennard

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Matthew Binns

Vagrancy of American terns to Europe 

The first record of American Black Tern for the Western Palearctic was a juvenile in Iceland in September 1950. Five more records followed in Iceland between 1956 and 1979, but it was not until 1999 that any were found elsewhere, when juveniles were in Dublin, Co. Dublin, in September and at Weston-super-Mare Water Treatment Works, Somerset, on 3rd–11th October. By the end of 2021, there had been a further seven birds in Britain (all in autumn) and 12 elsewhere in the Western Palearctic. All except five records related to juveniles; records of adults are limited to four records in Iceland and a bird feeding in Funchal harbour, Madeira, on 19th August 2007 (see http://madeira.seawatching.net/species/Chl_nig_sur/index.html). In addition, a first-summer was at Lady’s Island Lake and Carnsore Point, Co. Wexford, in July 2006 (Mullarney 2006). The Northumberland bird is the first record of a breeding-plumaged bird in Britain.

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Magnus Ullman (pers. comm.) said of the Madeiran bird: ‘We found the bird from a boat going out for a seawatch as it was foraging in Funchal harbour. The bird immediately struck us as “a Black Tern looking like a White-winged Black Tern”, so we asked the skipper to make an extra turn in the harbour for us to take some photos. The bird showed pitch-black underparts, just as black as the head, and we also got the impression of black coloration down the nape/mantle, unlike the grey tone of niger. Moreover, the leading edge of the wing was obviously and contrastingly white. At the time, we also concluded that the full breeding plumage in mid August suited surinamensis better than niger, which starts moulting the head in June. As far as I know, the bird was not seen again.’

Northumberland has a propensity for attracting rare terns owing to the county’s coastal Arctic, Common, Sandwich Thalasseus sandvicensis and Little Tern colonies. To date, an impressive list of vagrant terns has been recorded, most famously the Western Palearctic’s only Aleutian Tern Onychoprion aleuticus, on the Farne Islands on 28th and 29th May 1979, and the female Lesser Crested Tern T. bengalensis, ‘Elsie’, that returned to the Farne Islands each summer between 1984 and 1997. Other vagrant terns recorded in the vicinity of Northumberland’s tern colonies include Gull-billed Tern Gelochelidon nilotica, Caspian Tern Hydroprogne caspia, Bridled Tern O. anaethetus, Sooty Tern O. fuscatus, Whiskered Tern C. hybrida and White-winged Black Tern. However, there are still a number of species as yet unrecorded in the county: American Royal Tern T. maximus, African Royal Tern T. albididorsalis, Cabot’s Tern T. acuflavidus, Elegant Tern T. elegans, Least Tern and Forster’s Tern S. forsteri.

Of the 19 species of tern on the British List, only Sandwich Tern, Lesser Crested Tern, Little Tern, Whiskered Tern and White-winged Black Tern have breeding ranges that do not fall inside the Americas. The breeding ranges of several species fall entirely within the Americas: Royal Tern, Cabot’s Tern, Least Tern and Forster’s Tern. The breeding ranges of the other species listed in table 4, such as Arctic Tern, occur both in the Americas and in other parts of the world. Rare species in Britain, such as Gull-billed Tern, Caspian Tern, Sooty Tern and Bridled Tern, may reach Britain from a variety of compass points including the Americas and ringing recoveries have confirmed that individuals of species such as Cabot’s Tern and Caspian Tern have originated from North America. As the American subspecies/populations of these species differ only slightly, if at all from Western Palearctic populations, it is usually impossible to prove American origin unless the bird carries an American ring. However, as in the case of the Northumberland surinamensis, the dates and locations of occurrences in Britain may offer a clue regarding likely origin. For example, Gull-billed Tern occurs most frequently in Britain along the south coast and in East Anglia between May and August. October and November records of Gull-billed Tern are less frequent (comprising about 5% of the total) but several have occurred in regions where Gull-billed Tern is rare at other times of year, raising the possibility that these individuals could be of American origin. For example, Gull-billed Terns in Northumberland in October 2018, Argyll in September–October 2008 and Dumfries & Galloway in October 1990 may all relate to birds of American origin. That said, Gull-billed Tern is a scarce breeder in eastern North America, where fewer than 800 pairs are present (Ian Nisbet pers. comm.). As with American Black Tern, Forster’s Tern tends to be found at locations where, and at times of year (late autumn and winter) when, other tern species are scarce, and the species is likely to be overlooked in spring and summer given its similarity to Common Tern (Nisbet et al. 2013).

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European Black Tern has yet to be recorded as a vagrant to the USA, which may be because the subspecies is not on the radar of many birders there (Peter Pyle and Julian Hough pers. comms.). However, there is a record of a European Black Tern ringed in Germany in 1984 that was recovered in Brazil in 1986 (Sagot-Martin et al. 2020). 

Whiskered Tern has occurred in the Americas on three occasions, and White-winged Black Tern is more frequent (Lees & Gilroy 2021). I searched the Macaulay Library for photos of Black Terns in the USA and Canada in October, which returned 208 photos, nearly all of which were of juveniles. While the photos included some individuals that appeared pale, all photos appeared to be of American Black Tern.

It is fascinating to speculate on the point at which the Northumberland American Black Tern joined the Arctic Terns that it generally associates with in Northumberland. The majority of records of American Black Tern in Europe have been of juveniles that have arrived in the autumn, which are assumed to have recently crossed the Atlantic from the Nearctic, and the Northumberland American Black Tern perhaps arrived this same way. However, vagrant American Black Terns in Europe generally arrive here one to two months after the majority of Arctic Terns have departed Britain, and so the Northumberland bird was unlikely to have joined Arctic Terns initially on arrival. The bird may have joined Arctic Terns during their return migration in spring, or it may have migrated north separately and joined the Arctic Terns once in Britain. Alternatively, although Arctic Tern has a more southerly non-breeding distribution (primarily around Antarctica) than European Black Tern (coastal tropical Africa), some Arctic Terns remain off equatorial Africa in the winter (Hatch et al. 2020) and the Northumberland American Black Tern may have joined Arctic Terns in its first winter. 

Acknowledgments
Thanks to the following for reading early drafts of the article: Rich Andrews, Rupert Higgins, Chris Knox, John Martin, Keith Naylor, Ian Nisbet and Andy Stoddart. The following individuals helped with the Northumberland bird’s identification and details of previous records of American Black Tern in Europe: Peter Adriaens, Martin Collinson, Pierre-André Crochet, Kate Goodenough, Julian Hough, Yann Kolbeinsson, Daniel López-Velasco, Klaus Malling Olsen, Doug Pratt, Peter Pyle, Pedro Ramalho, Lars Svensson, Patricia Szczys, Magnus Ullman, Arnoud B. van den Berg and Nils van Duivendijk. 

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Ross Ahmed, Northumberland; e-mail [email protected]

Ross Ahmed picked up his first pair of binoculars just short of 30 years ago, when he was 11 years old. He has worked as an ornithologist for most of his adult life. He enjoys the challenge of finding birds in the field, particularly at his adopted patch of Holy Island and Lindisfarne NNR, Northumberland. However, he is equally at home behind a computer, where he savours working with numerical data to gain greater insights into topics such as bird distribution and identification.