Proposal (1032) to South American Classification Committee

Change current taxonomy of the genus Gygis: A) recognize subfamilies Gyginae and Anoinae within Laridae; B) split White Tern (Gygis alba) into three species; and C) revise English names for Gyginae

FOREWORD

Pratt's (2020) paper, which is the primary basis for this proposal, was to have been coauthored by Storrs L. Olson but the Covid-19 pandemic and resultant lockdown of the research divisions of the Smithsonian Institution prevented him from retrieving his notes on Gygis in time, and Pratt's paper was published only with some information cited as pers. comm. from Olson. Not long afterwards, Olson unfortunately fell ill and died (not from Covid). In June 2022, with the invitation and assistance of Helen James, Pratt located Olson's Gygis file in the Bird Division of the USNM, and took custody of it at the institution's request. Surprisingly (Olson had not mentioned it), the folder contained not only the expected data forms and correspondence, but also a nearly finished 6-page typed draft, prepared in April 1994, of a paper about species limits in Gygis. In an accompanying letter to the late Claudia Wilds, Olson stated his intention to submit the paper as soon as possible but for unknown reasons he never did so. The manuscript includes handwritten notations in red made by Wilds along with a letter from her with additional relevant comments. Copies of the MS plus Wilds's letter are attached herewith (following Lit. Cit., pp. 12-18). Combined, they provide two pre-molecular "voices from the grave" in support of the taxonomy proposed herein. Although we cite Olson's (MS) findings where they supplement other results, we urge the committee to read his entire original manuscript for the insights it contains, including a summary of Olson's detailed analysis of specimens in the American Museum of Natural History (from the Whitney South Sea Expedition) and the Smithsonian Institution (from the Pacific Ocean Biological Survey, POSB). The actual handwritten measurements that accompanied the Olson MS and can be supplied on request. Olson was quite prescient of genetic research that later confirmed his suggestions regarding the classification of Gygis and Anous.

This proposal consists of three parts, which can be voted on separately.

A) Recognize subfamilies Anoinae and Gyginae within the family Laridae.

Background: The SACC currently classifies Gygis and Anous among the terns (Laridae: Sterninae).

New information: Although fine branching details may differ, nearly all recent studies (Bridge et al. 2005, Pons et al. 2005, Baker et al. 2007, Cracraft 2013, Thibault and Cibois 2017, Černý and Natale 2022) and world checklists (HBW and Birdlife International 2022, Boyd 2024) recognize Gyginae and Anoinae as co-equal subfamilies with Larinae, and Sterninae within Laridae. (These authors also include Rhynchopinae which SACC regards as a separate family.) Olson (MS) anticipated this arrangement based on osteological and other morphological criteria. Thibault and Cibois (2017:246) produced a unified phylogeny based on four studies that produced identical basal branching patterns (a remarkable fact in and of itself):

Černý and Natale (2022) differed in showing Rhynchopinae in the most basal position and Gyginae and Anoinae as sister groups (but with a divergence well before that of the other subfamilies) and regard the five lineages as of equal subfamilial rank. Gill et al. (2024) place the noddies and Gygis in a basal position among typical terns but do not designate subfamilies. Boyd (2024) uniquely recognized Sternidae (terns including Sterninae and Gyginae) and Laridae (gulls including Larinae and Anoinae). Clearly, Howell and Zufelt's (2019) and Harrison et al.'s (2021) use of the term "white noddies" for Gygis is no longer acceptable.

Recommendation:

We recommend that the SACC bring its classification into line with the majority of those that recognize subfamilies by recognizing Anoinae and Gyginae as basal to other subfamilies within Laridae.

Note from Remsen: If this part of the proposal passes, then the Rynchopidae must also be ranked as a subfamily.

B) Split Gygis alba into three species.

Background: American Ornithologists' Union (1998 and Supplements) lists the genus Gygis as comprising a single species G. alba with three subspecies groups, alba, candida, and microrhyncha (extralimital for SACC). The differences of the form leucopes (Holyoak and Thibault 1974) were considered "minor" by Thibault and Cibois (2017), and they disregarded it, as do we. Subsequent authors have variously recognized one (Harrison et al. 2021), two (Pratt et al. 1987, del Hoyo and Collar 2014, Boyd 2024) or three (Olson 2005, Steadman 2006, Howell and Zufelt 2019, Pratt 2020, HBW and Birdlife International 2022) biological species within Gygis. Yeung et al. (2009), supplemented by Thibault and Cibois (2017), used mitochondrial genes to conclude that only one undifferentiated taxon of Gygis occurs in the Pacific Ocean, but Thomas et al. (2004) and Černý and Natale (2022) split G. microrhyncha (neither study included alba). For a discussion of discordance among molecular findings and between molecular and phenotypic data see Pratt (2020).

New Information:

ARCHAEOLOGY. Subfossil bones reveal that candida and microrhyncha were sympatric in prehuman times over a ca. 9,000 km swath of the tropical Pacific from Tinian in the Marianas to Easter Island. Here is the relevant text from Steadman (2006:400):

This alone establishes that these two taxa are separate species under the BSC. Thibault and Cibois (2017) suggested that Steadman (2006) merely divided a continuum of size at some arbitrary point and called larger specimens candida and smaller ones microrhyncha, but that idea either overlooks or ignores qualitative differences of which Steadman (2006) was clearly aware (Pratt 2020).

MORPHOLOGY AND COLORATION. The genus Gygis exhibits two strikingly different bill shapes, one resembling that of other small terns (Sterninae) and the other quite distinctive. Those of alba and microrhyncha are of the former type, with the loral feathering extending forward toward the nostrils and the malar feathering also extending forward into the mandible. The bill of alba is somewhat thicker at the base and the gonydeal angle somewhat more anterior, but otherwise the two are similar in shape and both are black throughout. The bill of alba is significantly larger than that of aptly named microrhyncha. The bill of the more familiar candida is intermediate in size and dagger-like or long triangular, with a basal insertion that forms a nearly straight line in profile. The anterior half is black but from the nostrils and gonydeal angle back, it is deep cobalt blue. These different bill shapes produce somewhat different head profiles. A picture being worth 10K words, here is Pratt's (2020) illustration:

The three forms of Gygis also differ in tail shape, with candida showing a more deeply forked tail than microrhyncha and alba intermediate (although closer to candida); and in the amount of pigmentation in the shafts of the outer primaries, with distinctly black shafts in candida but alba and microrhyncha showing less pigmentation that ranges from white to golden brown and occasionally to black (Wilds, in litt., pers. obs.).

VOCALIZATIONS. Pratt (2020) made the first detailed study of vocalizations, archived in Macaulay Library (ML;www.macaulaylibrary.org) and Xeno-canto (XC; www.xeno-canto.org), in Gygis. The voice of candida is well documented, but recordings of microrhyncha and alba are scarce and therefore must be used with caution in making comparisons. Nevertheless, Pratt (2020:204) concluded that each taxon in the genus has "a unique vocal repertoire easily distinguishable from the other two". The vocalizations of alba are particularly distinctive in being "strikingly lower pitched" than those of candida or microrhyncha with few obvious homologies. One vocalization (XC431354) appears to have no equivalent in either Pacific form. Although further research on vocalizations of alba and microrhyncha is needed, current knowledge suggests that vocal differences may well serve as isolating mechanisms among three species.

STATUS OF ALBA: The question of whether alba is a third species or conspecific with microrhyncha was addressed by Olson (MS), who concluded that the striking difference in size warranted species status. Pratt's (2020) observations on vocalizations add further evidence that alba is distinct. To date, no published genetic studies have included alba, but unpublished preliminary data from N. Yeung (pers. comm.) suggest that alba is genetically "very different". Obviously, this is fertile ground for further research.

Recommendation: Split Gygis alba into three species: G. alba (South Atlantic islands of Ascension, St. Helena, Fernando de Noronha, and Trindade); G. candida (tropical Indian and Pacific oceans); and G. microrhyncha (extralimital in Marquesas Islands south of Hatutaa, with historical occurrence in Kiribati). With this split, add G. candida to the South American Checklist.

C) Revise English names within Gyginae:

Background: As a single iconic species, G. alba has long been, and continues to be, called "fairy tern" by the lay public (Wilds, in litt.). That name has now been restricted by various "official" lists, including AOS, to Sternula nereis of southern Australia and New Zealand, but its use persists elsewhere for G. alba especially where the birds are conspicuous to large English-speaking populations. Even among those who use "White Tern", that name is often, perhaps usually, followed by some phrase such as "also known as fairy tern." In Honolulu, where the bird is an official city icon, the hybrid name "White Fairy Tern" has gained popularity as an informal way to get around the problem (see Pratt 2020 for references, especially Floyd 2019). Note that if we recognize 3 species of Gygis, the unmodified name White Tern should be reserved for the original unsplit species.

New information: All other Larid subfamilies, Anoinae (noddies), Larinae (gulls), Rhynchopinae (skimmers), and Sterninae (terns), have single-word group-names with their own separate listings in indexes. Use of "white terns" as a group-name, even if hyphenated, in our opinion fails to distinguish the Gyginae adequately from the Sterninae and will surely obfuscate. Pratt (2020) proposed the novel single word group-name "fairyterns", for the Gyginae to emphasize that they are NOT terns in the traditional sense, and leaving Fairy Tern (sometimes Austral Fairy Tern) for Sternula nereis. Note that "fairytern" has a subtly different pronunciation from "fairy tern". We are aware that this committee would ordinarily prefer the construct "fairy-tern" as did Pratt et al. (1987), but experience has taught us that indexers can be stubborn and idiosyncratic in such matters and may index the three species of Gygis among the true terns, hyphen notwithstanding. Thus "fairy-tern" is invested with the same problems as "white-tern". " Fairytern" allows no indexing option. This exception for Gygis is only necessary if the subfamily Gyginae is recognized (Part A). As Pratt (2020:206) observed, using "fairytern" will "allow non-professionals to maintain a beloved and widely used name without being scolded by pedants." Pratt (2020) proposed the English names Common Fairytern (G. candida), Little Fairytern (G. microrhyncha), and Atlantic Fairytern (G. alba) for the three species. We acknowledge that "Common" as an adjective in English bird names has met with some recent disfavor, but we believe it is particularly appropriate in this case because it is the fairytern most people will see, being vastly more widespread and common than the other two species, and the name has a long history of use in the Pacific (at least since Pratt et al. 1987). AOU (1998) uses "Pacific" for candida but that is geographically too restrictive. Howell and Zufelt (2019) suggested the epithet Indo-Pacific for G. candida, but, while accurate, it is something of a mouthful and unfamiliar to most potential users.

Recommendation: Assuming Part A is approved, adopt the English single word group-name "fairyterns" for the Gyginae, and the English names Atlantic Fairytern (G. alba), Common Fairytern (G. candida), and Little Fairytern (G. microrhyncha) for the subfamily's three species.

Literature Cited:

American Ornithologists' Union. 1998. Check-list of North American birds. 7th. Edition American Ornithologists' Union, Washington, DC.

Baker, A. J., S. L. Pereira, and T. A. Paton. 2007. Phylogenetic relationships and divergence times of Charadriiformes genera: multigene evidence for the Cretaceous origin of at least 14 clades of shorebirds. Biology Letters 3: 205-210.

Boyd, J. H., III. 2024. Taxonomy in flux: Version 3.49, June 19, 2024 (February 21, 2024). Accessed 4 August 2024.

Bridge, E. S., A. W. Jones, and A. J. Baker. 2005. A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage coloration. Molecular Phylogenetics and Evolution 35:459-469.

Černý, D., and R. Natale. 2022. Comprehensive taxon sampling and vetted fossils help clarify the time tree for shorebirds (Aves, Charadriiformes). Molecular Phylogenetics and Evolution 177: 107620.

Cracraft, J., 2013. Avian higher-level relationships and classification: Nonpasseriforms. In: Dickinson, E.C., Remsen, J.V. (Eds.), The Howard and Moore Complete Checklist of the Birds of the World, Volume 1: Non-passerines (4th edition). Aves Press, Eastbourne, UK, pp. xxi– xliii.

Del Hoyo, J., and N. J. Collar. 2014. HBW and BirdLife International checklist of the birds of the world. Vol. 1: Non-passerines. Lynx Edicions, Barcelona.

Gill F., D. Donsker & P. Rasmussen (Eds). 2024. IOC World Bird List (v14.1). doi: 10.14344/IOC.ML.14.1.

Floyd, T. 2019. How to know the birds: no. 20, Alien fairies in the big city. https://blog.aba.org/2019/11/how-to-know-the-birds-no-20-alien fairies-in-the-big-city.html. American Birding Association, Delaware City.

Harrison, P., M. Perrow, and H. Larsson. 2021. Seabirds: The new identification guide. Lynx Edicions, Barcelona.

HBW and BirdLife International. 2022. Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 7. Available at: http://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW - BirdLife_Checklist_v7_Dec22.zip

Holyoak, D. T., and J. C. Thibault. 1976. La variation geographique de Gygis alba. Alauda 44:457-473.

Howell, S. N. G., and K. Zufelt. 2019. Oceanic Birds of the World. Princeton University Press, Princeton and Oxford.

Pons, J.-M., A. Hassanin, and P.-A. Crochet. 2005. Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondrial markers. Molecular Phylogenetics and Evolution 37:686-699.

Pratt, H. D. 2020. Species limits and English names in the genus Gygis (Laridae). Bulletin of the British Ornithologists' Club 140:195-208.

Pratt, H. D., P. L. Bruner, and D. G. Berrett. 1987. A Field Guide to the Birds of Hawaii and the Tropical Pacific. Princeton University Press, Princeton, NJ.

Steadman, D. W. 2006. Extinction and Biogeography of Tropical Pacific birds. University of Chicago Press, Chicago.

Thibault, J.-C., and A. Cibois. 2017. Birds of Eastern Polynesia: a Biogeographic Atlas. Lynx Edicions, Barcelona.

Yeung, N. W., D. B. Carlon, and S. Conant. 2009. Testing subspecies hypotheses with molecular markers and morphometrics in the Pacific White Tern complex. Biological Journal of the Linnean Society 98:586-595.

Storrs Olson’s original MS with comments from Claudia Wilds:

Letter from Claudia Wilds to Storrs Olson:

H. Douglas Pratt and Eric A. VanderWerf (and Storrs L. Olson, posthumous contributor)

September 2024

_________________________________________________________________________________________________________

Comments from Stiles: “B. Gygis: Yes to recognizing the three species mentioned – and I found both Olson’s and Steadman’s comments exceptionally interesting.”

Comments from David Donsker (who has Bonaccorso vote): “C. NO. Although I am very sympathetic with Doug’s efforts to invent a new English name for these ethereal species which incorporates the delightful “Fairy Tern” in its construction, the compound word “fairytern”, in my opinion, smacks as an artificial and unnecessary neologism.

“The Australians have justifiably strong claims to use “Fairy Tern” for Sternula nereis so it is best to remove that name from use for Gygis species.

“White Tern” is now firmly established for Gygis, and perhaps though not as evocative nor as romantic as a name that includes “fairy”, is perfectly descriptive of these essentially pure white species. 

“I am not as concerned about the “indexing issues” as Doug writes.

“So, I vote NO to adopting “fairytern” for this group. Instead, I would prefer “white tern” or, if we must, “white-tern”. I would follow Doug’s recommended adjectives per his discussion (but I would certainly accept “Pacific” or “Indo-Pacific” White Tern for G. candida, if either of these two names were preferred over “Common” by the majority): 

Gygis alba Atlantic White Tern (White-Tern)

Gygis candida Common White Tern (White-Tern)

Gygis microrhyncha Little White Tern (White-Tern).”