Editing Bird migration (section)

{{Short description|Seasonal movement of birds}}
{{Redirect|Bird of passage||Bird of Passage (disambiguation)}}
{{Good article}}
{{EngvarB|date=July 2022}}
{{Use dmy dates|date=July 2022}}
[[File:BrantaLeucopsisMigration.jpg|thumb|300px|A flock of [[Barnacle goose|barnacle geese]] during autumn migration]]
[[File:Migrationroutes.svg |thumb|300px|Examples of long-distance bird migration routes]]

'''Bird migration''' is a seasonal movement of [[birds]] between breeding and wintering grounds that occurs twice a year. It is typically from north to south or from south to north. [[Animal migration|Migration]] is inherently risky, due to [[predation]] and mortality.

The [[Arctic tern]] holds the long-distance migration record for birds, travelling between [[Arctic]] breeding grounds and the [[Antarctic]] each year. Some species of [[Procellariiformes|tubenoses]], such as [[albatross]]es, circle the Earth, flying over the southern oceans, while others such as [[Manx shearwaters]] migrate {{convert|14,000|km|mi|sigfig=2|abbr=on}} between their northern breeding grounds and the southern ocean. Shorter migrations are common, while longer ones are not. The shorter migrations include [[altitudinal migration]]s on mountains, including the Andes and [[Himalayas]].

The timing of migration seems to be controlled primarily by changes in day length.  Migrating birds navigate using celestial cues from the Sun and stars, the Earth's magnetic field, and mental maps.