In recent weeks, the occurrence of a female Great-tailed Grackle on the Pembrokeshire coast at Nolton Haven has become one of the autumn's major talking points and sparked fresh debate about the status of ship-assisted vagrants on the British list.
Grackles form part of the Icteridae family, with members of the family found across the Neotropics and North America. Several members of the family, including Bobolink, Baltimore Oriole, Brown-headed Cowbird, Red-winged Blackbird and Yellow-headed Blackbird, are long-distance migrants that have reached the Western Palearctic (WP) on multiple occasions.
Members of the genus Quiscalus, grackles are typically social birds with iridescent black plumage. They are large and lanky, with long tails, pale irises and long and heavy bills. Females are brownish and less glossy than males. Three Quiscalus species are found in North America – and all three have been recorded in the WP.
Common Grackle is the most widespread species of grackle in North America and is ubiquitous in town cities of eastern states and the Midwest. It often nests in small colonies and forms large communal roosts outside of the breeding season. The species is partially migratory, with birds from the northern United States, Canada and the Great Plains moving south and east to winter in central and southern regions of the United States. It typically migrates in mixed-species flocks with Red-winged Blackbirds, Brown-headed Cowbirds and, amusingly, the introduced Common Starling. Further evidence of the species' migratory potential is provided by several records of birds reaching Bermuda, a British Overseas Territory in the North Atlantic Ocean more than 1,000 km from the east coast of North America. A number have also reached north-west Alaska.
Common Grackle has been recorded in Gibraltar (pictured), Denmark and the Netherlands (Jonathan Perera).
It is also the only species currently on Category A on the WP list, owing to a record of a male in active migration over Kamperhoek, the Netherlands, on 8 April 2013. The contrast between glossy purple-blue head and neck and glossy brown body meant it could be identified as belonging to the migratory subspecies versicolor, which breeds in Canada and the northern United States as winters as far south as Texas.
There is also a record from Gevninge, Denmark, between late March and 20 April 1970, though this record has not been accepted by the Danish rarities committee due to uncertainties about whether the bird was of wild origin. A male at Lathbury, Gibraltar, on 2 January 2010 was thought likely to have been ship assisted.
Boat-tailed Grackle is a large subtropical grackle found in saltmarsh habitat in the eastern United States. It has adapted well to human habitation, residing in urban areas and scavenging trash. Although largely sedentary throughout its range, some birds from northern portions of the breeding range move south to coastal Virginia and Florida for the winter.
Extralimital records are rare: one on the outskirts of Nashville, Tennessee, is the most notable, with a handful seen on boats off the New Jersey coast. Populations in the Bahamas, New Providence, Nassau and Paradise Island in the West Indies are thought likely to have become established via tour boat (Raffaele et al, 2020)
In March 2008, a female Boat-tailed Grackle was discovered at Kieldrecht, Belgium, although it was not added to the national list due to strong suspicions that the bird had not arrived there under its own steam. The village is situated close to the Port of Antwerp-Bruges, the second-largest port in Europe and the world's largest port for general cargo. This was followed by a first-winter female at Europa Point, Gibraltar, from 4-12 November 2014.
Great-tailed Grackle has also adapted well to areas of human habitation and is found across the south and west United States throughout Central America and the South American Pacific coast south to northern Peru. Since the mid-1900s, the species has undergone a rapid, large-scale range expansion which has followed the spread of irrigated agriculture and urban development into the Great Plains and western United States.
Pioneering birds at the leading edge of its range expansion can wander long distances, with the species having been recorded in 21 states and three Canadian provinces. One at Annapolis Royal, Nova Scotia, in 1983 was more than 2,000 km from the species' native range, with other incredible records seeing birds reach Akimiski Island, Nunavut, and Haida Gwaii, British Columbia.
The species regularly takes advantage of ships to travel around, with several birds having reached the island of O'ahu, Hawaii – undoubtedly as a result of constant shipping movements between the archipelago and the mainland United States. It is a recent colonist to several islands in the Caribbean (Hispaniola, Jamaica, Puerto Rico, San Andrés and Providencia) – all colonies establishing near major ports – with additional records on Aruba and Curaçao. In South America, birds thought likely to be ship assisted have reached Lima, Peru, and Chile (near Arica, Concepción and San Antonio) on several occasions, with single records from Paraty, Brazil, and Puerto Ayora, Galápagos.
Great-tailed Grackle regularly wanders via ship, with records across South America and the Caribbean (Sam Viles).
In the WP, birds thought to be ship assisted have reached Iberia on at least two occasions. One arrived in autumn 2014, photographed at Cadaqués, Catalonia, in late October, with an adult male discovered at Mazagón, Andalucia on 7 October 2022, remaining in the area until March 2023 at least. Two birds on Tenerife, Canary Islands, in early 2018 were deemed to be escapes, though a ship-assisted origin would seem equally likely. Additionally, an unassigned female Great-tailed/Boat-tailed Grackle was on a small ro-ro ferry at Bac de Barcarin in Camargue, France, between 25 September and 1 October 2013.
More recently, 25 October 2023 saw a female found in Britain at Nolton Haven. Residing predominantly in the village car park and on surrounding buildings, its sociable and confiding nature meant it attracted a steady procession of visitors during its five-day stay.
Nolton Haven is perfectly situated to attract a ship-assisted vagrant – Britain's largest energy port, Milford Haven, is just a short distance away. Oil tankers regularly anchor in St Brides Bay just off Nolton Haven while awaiting a berth and the preceding week before the bird's discovery saw no fewer than three arrive from the southern United States.
The Pembrokeshire Great-tailed Grackle is the first record for Britain (Sam Viles).
With the exception of Common Grackle, Quiscalus species are not typical long-distance migrants. Combined with the southerly distribution of Boat-tailed and Great-tailed Grackles, this makes both highly unlikely candidates for transatlantic vagrancy. Nevertheless, their gregarious, social nature and ubiquitous appearance in areas of human habitation means they are, however, strong candidates for ship assistance. In addition, the distribution of all three species correlates closely with well-established maritime traffic routes from the eastern seaboard and Mexico Gulf to Europe, and the majority of occurrences have been in the vicinity of major international ports. It is likely that further records of all three species will follow within the WP – most probably in close proximity to ports.
Raffaele, H, Wiley, J, Garrido, O, Keith, A, and Raffaele, J. 2020. Birds of the West Indies: Second Edition. Helm Identification Guides, London.