Changes to the British List (16 July 2025)
The British Ornithologists’ Union Records Committee (BOURC) has added a species to Category E.
The following species has been added to Category E:
Great-tailed Grackle Quiscalus mexicanus (Gmelin, JF, 1788)
One, female, at least first-calendar-year, Nolton Haven, Pembrokeshire, 25-29 October 2023 (photographed).
Photo (right): Great-tailed Grackle © Simon King
This Great-tailed Grackle was initially noted in the field by a non-birder and subsequently identified from photographs posted online. Later this identification was supported genetically by sequencing one mitochondrial gene.
Great-tailed Grackle is polytypic with eight subspecies recognised (IOC World Bird List (v 15.1)). Within Great-tailed Grackle there are two genetic groups and genetic sequencing of the bird in Pembrokeshire indicated that it belonged to a group which comprises the subspecies obscurus, monsoni, prosopidicola, nominate mexicanus, loweryi, and peruvianus (Condor 110: 170-177).
Great-tailed Grackle breeds from California to Oregon and east to Iowa, south to the Gulf of Mexico, and through Mexico and Central America, extending along the Caribbean coast from Colombia to northwestern Venezuela and along the Pacific coast from Colombia to northern Peru (Birds of the World). It is resident throughout most of its range, albeit with some evidence of partial migration at its northern range edge in the USA where it is expanding northwards (J. Biogeogr 30: 1593-1607).
Since 2014 at least seven other Great-tailed Grackles have been reported in the Western Palearctic in Spain (five including three in the Canary Islands), the Netherlands, and France (where a further grackle was either this species or the similar Boat-tailed Grackle Q. major) but it is not included on the national list of any of these countries (eBird).
Although Great-tailed Grackle has previously been held in captivity in Britain, it is not believed to be regularly held here or in mainland Europe, where no records have been considered to relate to escaped or released birds. Most European records of Great-tailed Grackle have been near ports or other locations along maritime traffic routes from North America and the Committee unanimously felt that the location of the British record within St Brides Bay, which transatlantic vessels routinely frequent for anchorage, indicated that this individual was ship-assisted. The species is extremely rare on the US eastern seaboard – where most records seem also likely to be ship-assisted – coming from port cities like St Petersburg and Miami in Florida and Plymouth in Massachusetts and this species has also been ship-assisted to Hawaii on multiple occasions (eBird).
Category A of the British List includes 61 species of Nearctic passerine from 15 families and 41 genera, but the range of Great-tailed Grackle is not comparable with any of them, and it is not a long-distance migrant (Ibis 148: 707-726, Ecology Letters 25: 581-597; Scientific Reports 15: 15456). BOURC’s current policy towards ship-assisted vagrants is not to admit port-to-port or coast-to-coast transportees onto the British List and suspected ship-assisted birds should only by admitted to the List if the species is considered capable of making an unassisted transatlantic crossing under favourable circumstances (Ibis 147: 246-250, Ibis 156: 236-242). In nearly all cases, the data are insufficient to draw a robust conclusion on this point, but the biology of Great-tailed Grackle makes unassisted vagrancy highly unlikely as it is largely non-migratory and does not occur in eastern North America.
Accordingly, Great-tailed Grackle has been added to Category E of the British List. Category E comprises those species that have been recorded as introductions, human-assisted transportees or escapees from captivity, whose breeding populations (if any) are thought not to be self-sustaining (Ibis 164: 860-910). Species listed in Category E form no part of the British List, unless they are also included in Categories A, B or C.
This change will be published as part of the BOURC’s 58th report due to be published in Ibis in January 2026. Upon publication of this change, the British List stands at 640 species (Category A = 623; Category B = 7; Category C = 10).