Pallas's leaf warbler now occurs regularly in Europe in autumn.
The first known European record was shot in 1829 in Dalmatia, now Croatia, but John Gould, who formally described it, did not realise the species had already been discovered in Asia, and named it as the "Dalmatian Regulus", Regulus modestus.
German ornithologist Heinrich Gätke, who moved to the then-British island of Heligoland in 1837 and stayed there for some fifty years, subsequently showed that several Asiatic species, including an occasional Pallas's leaf warbler, were regularly found there in autumn.

In the far west of Europe, the UK's first Pallas's leaf warbler was shot in 1896, although it was not until 1951 that the second was found.
Thereafter, this species became increasingly common, ceasing to be a national rarity at the end of 1990.
In 2003, for example, 313 were recorded in Britain.
Pallas's leaf warbler also occurs at least annually in Sweden, Finland and Denmark.

Most Pallas's leaf warblers found in Europe are first-year birds, and several reasons for the large increase in numbers in autumn have been proposed.
In the past, these warblers were widely considered to be vagrants or reverse migrants, but were more recently thought to be undertaking a regular migration, taking advantage of the mild oceanic climate on the western fringes of Europe for overwintering.
A flaw in that theory is that many birds should winter in Spain, particularly in the northwest, but Pallas's leaf warbler is rare in that country and tends to occur in the east.
Spanish ornithologist Eduardo de Juana has therefore proposed that once the warblers reach northwest Europe, they then reorientate to a south easterly direction.

Outside Europe, Pallas's leaf warbler has been recorded as a vagrant in north Africa (Tunisia and Morocco), western Asia (Israel, Turkey and Iran), central Asia (Uzbekistan and Tajikistan), southeast Asia (Bangladesh and Taiwan), and Alaska.
Pallas's leaf warbler now occurs regularly in Europe in autumn. The first known European record was shot in 1829 in Dalmatia, now Croatia, but John Gould, who formally described it, did not realise the species had already been discovered in Asia, and named it as the "Dalmatian Regulus", Regulus modestus. German ornithologist Heinrich Gätke, who moved to the then-British island of Heligoland in 1837 and stayed there for some fifty years, subsequently showed that several Asiatic species, including an occasional Pallas's leaf warbler, were regularly found there in autumn.
In the far west of Europe, the UK's first Pallas's leaf warbler was shot in 1896, although it was not until 1951 that the second was found. Thereafter, this species became increasingly common, ceasing to be a national rarity at the end of 1990. In 2003, for example, 313 were recorded in Britain. Pallas's leaf warbler also occurs at least annually in Sweden, Finland and Denmark.
Most Pallas's leaf warblers found in Europe are first-year birds, and several reasons for the large increase in numbers in autumn have been proposed. In the past, these warblers were widely considered to be vagrants or reverse migrants, but were more recently thought to be undertaking a regular migration, taking advantage of the mild oceanic climate on the western fringes of Europe for overwintering. A flaw in that theory is that many birds should winter in Spain, particularly in the northwest, but Pallas's leaf warbler is rare in that country and tends to occur in the east. Spanish ornithologist Eduardo de Juana has therefore proposed that once the warblers reach northwest Europe, they then reorientate to a south easterly direction.
Outside Europe, Pallas's leaf warbler has been recorded as a vagrant in north Africa (Tunisia and Morocco), western Asia (Israel, Turkey and Iran), central Asia (Uzbekistan and Tajikistan), southeast Asia (Bangladesh and Taiwan), and Alaska.
Pallas's leaf warbler