Bird orientation at high latitudes: flight routes between Siberia and North America across the Arctic Ocean

Abstract

Bird migration and orientation at high latitudes are of special interest because of the di¤culties associated with di¡erent compass systems in polar areas and because of the considerable di¡erences between £ight routes conforming to loxodromes (rhumblines) or orthodromes (great circle routes). Regular and widespread east-north-east migration of birds from the northern tundra of Siberia towards North America across the Arctic Ocean (without landmark in£uences) were recorded by ship-based tracking radar studies in July and August. Field observations indicated that waders, including species such as Phalaropus fulicarius and Calidris melanotos, dominated, but also terns and skuas may have been involved. Analysis of £ight directions in relation to the wind showed that these movements are not caused by wind drift. Assuming possible orientation principles based on celestial or geomagnetic cues, di¡erent £ight trajectories across the Arctic Ocean were calculated: geographical loxodromes, sun compass routes, magnetic loxodromes and magnetoclinic routes. The probabilities of these four alternatives are evaluated on the basis of both the availability of required orientation cues and the predicted £ight paths. This evaluation supports orientation along sun compass routes. Because of the longitudinal time displacement sun compass routes show gradually changing compass courses in close agreement with orthodromes. It is suggested that an important migration link between Siberia and North American stopover sites 1000^2500 km apart across the Arctic Ocean has evolved based on sun compass orientation along orthodrome-like routes.

Radar Observations of Arctic Bird Migration at the Northwest Passage, Canada

“…Our results demonstrate that the migration patterns in High Arctic Canada are much more complex than those along the Northeast Passage (Alerstam and Gudmundsson, 1999a). At the Northeast Passage, there is a major and clear-cut migratory divide at the most northerly peninsula (Taymyr) of the Eurasian continent (about longitude 100 -110˚ E), with eastward migration strongly dominating to the east of this divide and westward migration to the west of it (Alerstam and Gudmundsson, 1999a).…”

“…Our methods were virtually the same as those used in an earlier study along the Northeast Passage (Alerstam and Gudmundsson, 1999a), allowing a direct comparison of the results between the two studies.…”

“…At the Northeast Passage, there is a major and clear-cut migratory divide at the most northerly peninsula (Taymyr) of the Eurasian continent (about longitude 100 -110˚ E), with eastward migration strongly dominating to the east of this divide and westward migration to the west of it (Alerstam and Gudmundsson, 1999a). In contrast, eastward movements are important throughout the whole of Arctic North America, but there are also sites and occasions with significant migration towards the west, north, and south (Table 2, Fig.…”

“…The outward and return journeys took place along different routes, and the return journey included a visit to the current position of the North Magnetic Pole (Molau et al, 1999;Grönlund, 2000). Our way of conducting these studies was essentially the same as on a previous expedition along the Northeast Passage in 1994 (Alerstam and Gudmundsson, 1999a;Alerstam and Jönsson, 1999), and one important objective for the present study at the Northwest Passage was to compare bird migration between these two major tundra regions in the Old World and New World, respectively. This paper presents our radar results and field observations for each study site and summarizes the distributions of directions, altitudes, and speeds of bird migration over the whole region.…”

“…This paper presents our radar results and field observations for each study site and summarizes the distributions of directions, altitudes, and speeds of bird migration over the whole region. We evaluate observed flight directions and routes in relation to the migration systems of shorebirds, jaegers, and terns in the New World (e.g., Morrison, 1984) and compare altitudes and speeds with the corresponding information for tundra migrants at the Northeast Passage (Alerstam and Gudmundsson, 1999a) and for shorebirds at Nova Scotia (Richardson, 1979). In separate papers, we have evaluated the possible orientation mechanisms by analyzing observed flight directions in relation to trajectories predicted from different celestial and geomagnetic orientation cues (Alerstam et al, 2001); examined the effect of wind drift on the birds' flight directions (Green et al, unpubl.…”