The red-eyed vireo, which weighs less than an ounce, has been recorded far more often than any of the 43 other types of Canada or United States- nesting landbirds that have turned up in Britain and Ireland since the mid 1960s.
A new league table shows that this 6in-long greenish-coloured songbird is overwhelming champion with 107 British Isles appearances in the past three decades - more than twice the number of its nearest rival.
The runner-up is the grey-cheeked thrush with 43 sightings, followed by the yellow- billed cuckoo with 35, the blackpoll warbler with 34, the rose-breasted grosbeak with 22 and Swainson's thrush with 20. The rest turned up fewer than 20 times, with most in single figures. According to the report in the latest edition of British Birds, 73 of the vireos appeared here between 1987 and 1996. The top year was 1995 when 21 were discovered, with 12 in 1988, 10 in 1990 and 1996, and 1 to 6 in each of the other years.
Meanwhile more have been flying into other parts of Europe - with record numbers in Iceland, Holland, Germany, Belgium, France and Malta - and one reached Morocco.
Norman Elkins, who produced the report, says that of 17 American songbirds seen around the British Isles during 7-12 October 1995, 11 were vireos - and the evidence suggested the first of them left the United States on 3 October.
These birds travelled thousands of miles off course from their normal autumn migration route from the USA and Canada to the West Indies and Central and South America.
Mr Elkins says this wrong turning could be due to a tendency to go north- eastwards - towards Europe - if they meet a weather pattern comprising south-westerly winds ahead of a cold front.
The large number recorded in 1995 "supports this possibility", he adds. Weather maps for the period show warm south-westerlies developed ahead of the westernmost cold front as it began to return northwards as a warm front. The decrease in the general flow of American songbirds to Europe could be caused by population decreases linked to loss of forest habitat in both their northern nesting and tropical wintering regions. Against this trend, red-eyed vireo populations are reported to have increased in north-east America.
Of the Vireonidae family, warbler-like but more closely related to shrikes.Nests in Canada and northern USA, winters in South America south to northern Argentina. Mainly eat insects.
Of the Catharus genus, the nightingale-thrushes. Summers from Newfoundland to Siberia. Winters in South America. Food includes insects, snails and fruit.
Of the non-parasitic cuckoo sub-family Phaenicophaeinae. Summer range from Canada to Mexico. Winters from Venezuela and Colombia south. Eats insects, caterpillars and fruit.
Part of the Parulidae family of wood warblers but not related to European warblers. Summer range from Alaskato New York, winters from Panama southward. Eats insects and fruit.
Rose-breasted grosbeak (Pheucticus ludovicianus)
Of the Cardinalinae sub-family, part of the wider bunting family. Summer range from central Canada to New England, winters from Mexico to Ecuador. Eats insects, fruit and seeds.
Of the Catharus genus, the nightingale-thrushes. Summer range from Alaska to Appalachia, winters from Mexico to Argentina. Eats insects, worms, snails, slugs and fruit.Reuse content