Order Now To Get A Special 7O% OFF

http://vertigodiss.za.com/Wfn9Rmzp3vOKKHrWbA9ncm5pKQMtZSnEnOYvFKJrw4tpuRwhWg

http://vertigodiss.za.com/VIm8Z8tuzSg9ux4t90l4Kk63RQAUAjXCxD_4nXAp-LdNH_uK2Q

ration 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. 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 tubenoses, such as albatrosses, circle the Earth, flying over the southern oceans, while others such as Manx shearwaters migrate 14,000 km (8,700 mi) between their northern breeding grounds and the southern ocean. Shorter migrations are common, while longer ones are not. The shorter migrations include altitudinal migrations on mountains such as 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.

Historical views
Writings of ancient Greeks recognized the seasonal comings and goings of birds. Aristotle wrote that birds transmuted into other birds or species like fish and animals, which explained their disappearance and reappearance. Aristotle thought many birds disappeared during cold weather because they were torpid, undetected in unseen environments like tree hollows or burrowing down in mud found at the bottom of ponds, then reemerging months later. Still, Aristotle recorded that cranes traveled from the steppes of Scythia to marshes at the headwaters of the Nile, an observation repeated by Pliny the Elder in his Historia Naturalis.

Two books of the Bible may address avian migr