 Prior to its extinction , at least some birds were present year @-@ round on the island , relying on warm volcanic springs to survive through the coldest months , but this race was also found in winter in the Faroe Islands and Ireland , and on passage through the Western Isles , suggesting that the Icelandic form was a partial migrant . The nominate subspecies , R. a. aquaticus is resident in the milder south and west of its range , but migrates south from areas that are subject to harsh winters . It winters within its breeding range , and also further south in North Africa , the Middle East and the Caspian Sea area . The peak migration period is September to October , with most birds returning to the breeding grounds from March to mid @-@ April . A specimen of the nominate population labelled as " Baluchistan " and collected by Richard Meinertzhagen is considered of doubtful provenance . R. a. korejewi is another partial migrant , with some of the population wintering from Iraq and eastern Saudi Arabia eastwards through Pakistan and northern India to western China . 
