Changes in wintering areas evidence from ringing

Among the irruptive species studied, return to wintering sites in later years was even rarer than return to breeding sites (Table 18.2). Despite some very large numbers ringed (often in small gardens), return rates of seed-eaters were mostly nil or less than 1% (but with Purple Finch Cardopdacus purpureus at 5 % in one area). Evidently, extremely few individuals of such species returned to the same localities in subsequent years. They showed little or no winter site-fidelity, compared with regular migrants (Chapter 17).

Among Eurasian species, although some ringed individuals were found in the same area in successive autumns or winters, indicating fidelity to the same migration or wintering sites (for Brambling Fringilla montifringilla, Eurasian Siskin Carduelis spinus, Common Redpoll Carduelis flammea and Eurasian Bullfinch Pyrrhula pyrrhula, see Cramp & Perrins 1994), other individuals were found in widely separated sites in different years. Most captures of the same individuals in successive winters lay at localities on the same migration axis, as mentioned above (including some more than 3000 km apart), but others included substantial east-west displacements. Extreme examples included a Bohemian Waxwing Bombicilla garrulus found in Poland one winter and in Siberia in a later winter (6000 km apart), a Pine Siskin Carduelis pinus found in Quebec in one winter and in California in a later winter (3950 km apart), and a Common Redpoll Carduelis flammea found in Belgium in one winter and in China in a later one (8350 km apart) (Table 18.3). Another Common Redpoll was recorded in North America in one winter and Eurasia in a later winter, having been ringed in Michigan and recovered near Okhotsk in Siberia, some 10 200 km to the northwest (Troy 1983). All these birds are likely to have returned to the breeding range in the interim (though not necessarily to the same locality), and taken a markedly different migration direction in the second year. Further records of this type are given in Box 18.2.

North American ringing records also reveal the transcontinental nature of boreal finch movements. Although most species breed across the entire continent in boreal forest, populations breeding in Alaska and other parts of the northwest tend to migrate east-southeast to winter in the eastern States. Birds from eastern Canada migrate south-southwest to also winter in the eastern States, the same region as the western birds (Brewer et al. 2000). Many of the records of individual Common Redpolls Carduelis flammea and Pine Siskins Carduelis pinus found on opposite sides of the continent in different winters (Troy 1983, Kaufman 1984) may therefore represent northwestern breeders that remain in the northwest in one year and migrate far along their east-southeast route in another year. However, some individuals have been recovered well south of the boreal forest on different sides of the continent in different winters, indicating that they had taken different directions from the breeding range in different years. For example, a Cedar Waxwing Bombycilla cedrorum ringed in California one April was recovered in Alabama 3000 km to the east two years later (for other interesting ringing records from North American species see Box 18.2).

Table 18.3 Examples of irruptive species in widely separated localities in different winters (December-March)

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