Bird migration

Lore & Background

In Samoan tradition, Tagaloa sent his daughter Sina to Earth as a bird, Tuli, to find dry land, with tuli referring to land-finding waders, often the Pacific golden plover. Only at the end of the eighteenth century was migration accepted as the explanation for winter bird disappearance.

Reader's Guide

Bird migration is a key biological phenomenon involving regular seasonal movement, often north and south, between breeding and non-breeding areas. The primary motivation appears to be food availability, with longer northern summer days allowing extended feeding of young. These advantages offset high stress, physical exertion, and risks such as predation—exemplified by Eleonora's falcon, which times its breeding to feed on southbound passerine migrants. Partial migration occurs within species, with some populations migratory and others sedentary. Migration patterns include leap-frog and chain migration, and most birds migrate in flocks, which reduces energy costs; geese in V formation conserve 12–20% energy. The timing is controlled primarily by day length, and navigation uses celestial cues, Earth's magnetic field, and mental maps. The Arctic tern holds the long-distance record, traveling between Arctic and Antarctic each year. Understanding migration has grown from ancient observations to modern tracking, but the phenomenon remains a subject of ongoing study.

Did You Know?

• The Arctic tern holds the long-distance migration record, traveling between Arctic breeding grounds and the Antarctic each year.
• Eleonora's falcon breeds on Mediterranean islands and coordinates its late breeding season with the autumn passage of southbound passerine migrants, which it feeds to its young.