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Figure 6.4 Density (length of arrow) and main direction (azimuth of arrow) of nocturnal bird migration above moon-watch sites indicated by the origins of the arrows. The numbers beneath the maps show the total number of migrants (in millions) that passed in each season through the fronts delimited by the brackets. Large water bodies are indicated in blue, the largest being the eastern part of the Caspian Sea at the left and the Aral Sea at longitude 60°E. Mountain ranges are shaded grey; the Elburz range is at the lower left; the Hindu Kush, the Pamirs and the Tien Shan respectively are eastward from about 65°E. In autumn, birds mostly crossed the mountain ranges (then at their best), avoiding the dry deserts to the west; but in spring they mostly crossed the deserts (then at their most lush) and avoided the mountains (then snow-covered). Redrawn from Dolnik (1990).

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