unnamed (35)

Across the eastern and especially the central portions of the continent, the efficiency of nocturnal migration is projected to increase in the spring and decrease in the autumn, potentially affecting time and energy expenditures for many migratory bird species. Warmer colors (red, orange) indicate stronger wind assistance. Cooler colors (purple, blue) show decreased wind assistance for bird flight. Graphic by Frank La Sorte, Cornell Lab of Ornithology.