Spring arrival of passerine migrants in Iceland

Abstract

First sightings in Iceland throughout the 20th century of four summer migrant passerines were studied for possible changes in arrival dates over time, and to relate arrivals to weather conditions in Iceland and in their probable wintering and staging areas. Arrival dates advanced considerably until the 1930s, as Icelandic seasonal temperatures increased. Temperatures and arrival dates changed much less in later years, when Icelandic temperatures showed no sustained trends. Since 1950, Redwings Turdus iliacus coburni have first been seen in the last week of March, Meadow Pipits Anthus pratensis and White Wagtails Motacilla a alba about 20 April and Wheatears Oenanthe o leucorhoa about 25 April. All four species were usually seen earlier when springs in Iceland were warm and wet, and after warm winters in southern Spain. Limited records of departures in autumn suggest that the mean lengths of stay in 1951–2000 were: Redwing 233 days, Meadow Pipit 164, White Wagtail 162 and Wheatear 144 days. Sightings of Redwings and Meadow Pipits, some of which winter in Britain & Ireland, were earlier after warm winters, and during warm springs, in central England. White Wagtails and Wheatears, wintering in Africa, showed no response to English temperatures. First sightings were most likely when winds over Iceland had easterly or southerly components. In 1951–1970 arrivals of Redwings and Meadow Pipits were earlier after winters in which the North Atlantic Oscillation index had been positive and high, but before and after that period no linkage was apparent. Most of these findings resemble those reported from north Norway, though the populations of at least three of the species are probably different. They are unlike the findings from Britain and western Europe, where dates of arrival have advanced most rapidly in recent years while winter and spring warming has continued.