The Status and Occurrence of Least Tern (Sternula antillarum) in British Columbia. By Rick Toochin and Don Cecile. Revised: August 10, 2024.

 

The Least Tern (Sternula antillarum) is listed as a species of concern, threatened, or endangered throughout its breeding range depending on the specific population that is described due to habitat loss through the birds breeding range (Thompson et al. 1997). The largest population of Least Tern is found along the Gulf of Mexico and into the Mississippi Drainage basin and has the status of “species of concern” (Thompson et al. 1997). Another breeding population of Least Tern breeds along the Atlantic Coast from Maine to Florida; and this population is listed either as endangered or threatened (Thompson et al. 1997). The last breeding population of Least Tern is found in southern California; and this endangered population only has about 600 birds (Thompson et al. 1997). The Least Tern is a species that is prone to wandering (Thompson et al. 1997). There are records from Ontario to Newfoundland in eastern Canada (Dunn and Alderfer 2011). In the mid-west the Least Tern is casual north of its breeding range with records from Alberta, Saskatchewan and Manitoba (Thompson et al. 1997).

 

On the west coast north of California, the Least Tern is an accidental vagrant species. In Oregon, there are 9 records accepted by the Oregon Bird Records Committee (OFO 2012). In Washington State, there are 5 records accepted by the Washington Bird Records Committee (Wahl et al. 2005, WBRC 2012). In British Columbia, the Least Tern is an accidental vagrant with only a couple of Provincial records (Toochin et al. 2014). There are no records for Alaska or the Yukon (Sinclair et al. 2003, Gibson et al. 2013).

The identification of the Least Tern is covered in all standard North American Field Guides. This is North America’s smallest species of tern measuring 23 cm in length with a wingspan of 51 cm (Olsen and Larson 1995). There is no other species that regularly occurs in British Columbia that looks similar to the Least Tern, making identification fairly straightforward. The similar looking Little Tern (Sternula albifrons) found in Eurasia is out the scope of this article. Readers are encouraged to check out Olsen and Larson (1995) for how to separate the Little Tern from the Least Tern.

 

The adult Least Tern in breeding plumage holds its plumage from March to September (Sibley 2003). In this plumage, the adult has a white forehead with a black cap that extends down the nape (Sibley 2003). There is a black line from the base of the bill that goes through the dark eye and connects to the black of the nape (Dunn and Alderfer 2011). The bill is thick at the base, but is tapered to a fine tip and is yellow-orange with a black tip (Olsen and Larson 1995). The throat down to the breast to the undertail coverts is white (Olsen and Larson 1995). The legs are short and yellow as are the feet (Sibley 2003). The back is gray and this extends down to the rump (Olsen and Larsson 1995). The folded wings are gray, with black primaries (Olsen and Larson 1995). In flight, the upper wing is pale gray with the leading edge of the primaries black giving the outer wing a distinct black-lined look or dark wedge to the outer wing (Olsen and Larson 1995). The underside of the wing is white except for the darker primary feathers (Sibley 2003). The Least Tern flies with very shallow and rapid wing beats (Sibley 2003). The tail is short and heavily forked (Olsen and Larson 1995).

 

The juvenile plumage of the Least Tern is held from July to September (Sibley 2003). Juvenile birds show brownish “U”- shaped barred markings on the back (Olsen and Larson 1995). The crown is dusky streaked (Olsen and Larson 1995). The bill is mostly black with a light edge at the inner base of both the upper and lower mandibles (Olsen and Larson 1995). There is a distinct dark line from the dark eye that extends towards the nape (Sibley 2003). The wings have a dark carpal bar and dark primaries that have light edges (Olsen and Larson 1995). The rest of the wing is light with brownish edges (Sibley 2003). In flight, the upper wing has light secondaries, a dark leading edge and primaries that give the wing a dark “M” pattern (Sibley 2003). The underside of the wing is white (Sibley 2003). The tail is white and forked (Olsen and Larson 1995). The legs are a light yellow-orange (Olsen and Larson 1995).

 

First year plumage is held from September to July (Sibley 2003). These birds have a black bill, white forehead and a dark line that extends from the dark eye to and across the nape (Sibley 2003). There is a thin dark carpal bar (Olsen and Larson 1995). The back and wings are gray, except the black primary feathers (Olsen and Larson 1995). The throat is white, and this white extends down the breast to the undertail coverts (Sibley 2003). The tail is forked and white (Sibley 2003). The legs are dark with a yellow tinge (Olsen and Larson 1995).

The calls of the Least Tern include a high-pitched “kip” and a harsh “chir-ee-eep”(Sibley 2003). The alarm call is a sharp sounding “zreek” (Sibley 2003).

In British Columbia, the Least Tern is an accidental vagrant with only 4 Provincial records (Campbell et al. 2001, Toochin et al. 2014). All Provincial records of the Least Tern come from the months of June and July (Toochin et al. 2014). The first record was an adult bird found by Mike and Sharon Toochin on June 6, 1997, at the end of Road 22, in the south Okanagan Valley (Shepard 1998, Campbell et al. 2001). The bird remained in the area until the next day allowing many observers to see it (R. Toochin Pers. Obs.). The second record was an adult bird that was found and photographed by Robert McMorran on June 24, 2010, at Sandspit Airport, in the Queen Charlotte Islands (Charlesworth 2010, Toochin et al. 2014). The third record was an adult found and photographed by Brian Self, Kevin Louth, Roger Foxall and Philip Wright near 96th Street in Boundary Bay, Delta on July 12, 2024 (D. Cecile Pers. Comm.). Shortly after this record the fourth provincial record involving 2 adult birds was found and photographed by Scott Thomson and was relocated by other observers east of Lumby at Rawlings Lake (D. Cecile Pers. Comm.). The timing of all the Provincial records to date is mirrored in Oregon and Washington State where the occurrence of the Least Tern has been predominantly from May – July (OFO 2012, WBRC 2012). The origin of both birds is impossible to know, but there are so few birds found in southern California, it would seem more likely they originated from the Mississippi region (J. Fenneman Pers. Comm.). Either way these birds were a great distance from where they are normally found. Given the wandering tendencies of this species throughout Eastern North America, it seems logical another Least Tern will turn up in British Columbia in the future. It is a species that can turn up anywhere in the Province.

1.(1) adult June 6-7, 1998: Mike Toochin, mobs (BC Photo 1635) north end of Osoyoos Lake (Shepard 1998, Campbell et al. 2001)

2.(1) adult June 24, 2010: Robert McMorran (photo) Sandspit, Haida Gwaii (Charlesworth 2010, Toochin et al. 2014)

3.(1) adult July 12, 2024: Brian Self, Kevin Louth, Roger Foxall and Philip Wright (photo) near 96th St at Boundary Bay, Delta (D. Cecile Pers. Comm.)

4.(2) adults July 24, 2024: Scott Thomson, mobs (photo) east of Lumby at Rawlings Lake (D. Cecile Pers. Comm.)

We want to thank Jamie Fenneman for further information on Least Tern vagrancy. I wish to thank Jo Ann MacKenzie for giving me permission to use her Least Tern images from the south Okanagan record. We also want to thank Robert McMorran for giving us permission to use his images of a Least Tern he found and photographed from Sandspit Haida Gwaii. All photos are used with permission of the photographer and are fully protected by copyright law.

 

Campbell, R. W., N. K. Dawe, I. McTaggart-Cowan, J. M. Cooper, G. W. Kaiser, A. C. Stewart, and M. C. E. McNall. 2001. The Birds of British Columbia – Volume 4 (Passerines [Wood-Warblers through Old World Sparrows]). Vancouver: UBC Press.

 

Charlesworth, C.  2010. summer season– British Columbia. North American Birds 64: 636-637.

 

Dunn, J. L. and J. Alderfer. 2011. National Geographic Field Guide to the Birds of North America. National Geographic Society, Washington D.C. 574pp.

Gibson, D.D, L. H. DeCicco, R. E. Gill Jr., S. C. Heinl, A. J. Lang, T. G. Tobish Jr., and J. J. Withrow. 2013. Checklist of Alaska Birds. 19th Edition: 2013. [Online Resource] Retrieved from http://www.universityofalaskamuseumbirds.org/products/checklist.pdf [Accessed: December 16, 2014].

 

OFO. 2012. Oregon Field Ornithologists - Records Committee. [Online resource] http://www. oregonbirds.org/index.html. [Accessed: June 10, 2015].

 

Olsen, K. M. and H. Larsson. 1995. Terns of Europe and North America. Princeton University Press, Princeton, NJ. 207pp.

 

Shepard, M. G.  1998. The summer season – British Columbia – Yukon region. North America Birds 52: 493-494.

 

Sibley, D. A. 2003. The Sibley field guide to birds of Western North America. Alfred A. Knopf, New York. 273pp.

 

Sinclair, P. H., W. A. Nixon, C. D. Eckert, N. L. Hughes (eds.) 2003.Birds of the Yukon Territory. U.B.C. Press, Vancouver, British Columbia. 596pp.

 

Thompson, Bruce C., Jerome A. Jackson, Joannna Burger, Laura A. Hill, Eileen M. Kirsch and Jonathan L. Atwood. 1997. Least Tern (Sternula antillarum), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology [Online Resource] Retrieved from: the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/290 [Accessed: May 2, 2015].

 

Toochin, R., J. Fenneman and P. Levesque. 2014. British Columbia rare bird records: January 1, 2014: 3rd Edition. [Online resource] Retrieved from http://www.geog.ubc.ca/biodiversity/efauna/documents/BCRareBirdListJanuary2014XZBC.pdf [Accessed: June 10, 2015].

 

Wahl, T. R. , B. Tweit and S. Mlodinow. 2005. Birds of Washington: Status and Distribution. Oregon State University Press, Corvallis, Oregon. 

 

WBRC. 2012. Washington Bird Records Committee – Summary of Decisions. Washington Ornithological Society, Seattle, WA. [Online resource]  http://www.wos.org/wbrcsummaries.html. [Accessed: June 10, 2015].