loxodrome

A common feature at almost all sites is that the recorded tracks to a large extent were directed to the north of the loxodrome courses towards Nova Scotia (except at sites Y and Z, where differences between observed track directions and calculated courses along loxodromes as well as orthodromes were minor) (Table 5).

Observed track directions of eastward and southward migration in relation to the orthodrome and loxodrome courses towards Nova Scotia from different sites.

Radar studies could also help us to investigate whether the birds' migration routes conform to great circles (orthodromes), which are significantly shorter than rhumb lines (loxodromes) at polar latitudes, and to evaluate the observed flight routes in relation to the orientation difficulties encountered in this area because of extreme geomagnetic field conditions close to the North Magnetic Pole.

The track directions of eastward and southward migration at the different sites are summarized in relation to the calculated courses towards Nova Scotia along orthodromes (the departure course is given) and loxodromes in Table 5, which also gives the distances from the different sites to Nova Scotia.

This has the consequence that magnetic loxodromes (tracks with constant magnetic compass courses) curve unfavourably (prolonging flight distances) in the Taymyr sector, while they curve in a distance-saving way (compared to geographic loxodromes, i.e., tracks with constant geographic courses) on either side of this region.

Since the birds migrating E/W along the Northeast Passage do not follow courses that point along geographic loxodromes directly towards their ultimate winter destinations, one may ask what are their intermediary destinations and passage areas in the arctic region?

On the Mercator projection, the arrows indicate extrapolated flight routes if the birds maintain constant geographic courses and thus fly along loxodromes (which are shown as straight lines on a Mercator projection).