Ecology of tundra birds: Patterns of distribution, breeding and migration along the Northeast Passage

Several different aspects of the geographical ecology of tundra birds were investigated during the Swedish-Russian Tundra Ecology -94 expedition along the Northeast Passage in 1994. Quantitative censuses of breeding bird comm unities and populations were made at the temporary field sites, supplemente d by surveys from helicopter over wider tundra areas. The occurrence of avi an predatory species-skuas, snowy owl and rough-legged buzzard-was analyzed with respect to interspecific relationships as well as to the abundance of their main prey, the lemmings. Geographical variation in color phases amon g skuas and of genetics in dunlins (based on mitochondrial DNA) were examin ed, as well as the social organization in different wader species and moult strategies among populations of dunlins;Bird migration was recorded by a t racking radar placed on the expedition ship, and by complementary visual ob servations. These studies demonstrated the patterns of flight directions, a ltitudes, speeds (also measured by optical instruments) and migratory route s of the tundra birds. Ringing results contributed to put these results int o a global migratory perspective. Two important aspects of the energetics o f arctic birds were investigated during the expedition: the basal metabolic rates of waders when departing on migration, and the fuel loads deposited by the migrating waders. The effect of longitudinal displacement on the mig ratory orientation of a long-distance passerine migrant, the wheatear, was tested by repeated orientation experiments at a number of test sites along the Northeast Passage.