A World on the Wing by Scott Weidensaul review – incredible journeys taken by migratory species

A World on the Wing by Scott Weidensaul review – incredible journeys taken by migratory species

The Guardian

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The acclaimed natural history writer amply conveys his joy and amazement at the ability of birds to navigate the hemisphere

Among the mysteries of migration unfolded by the renowned natural history writer Scott Weidensaul in his new book is the song of the male red knot. This rises in reflection of its expanding genitalia – “shrunken and all but functionless” during the months it spends in Australia, then swelling as it flies north towards its Siberian breeding grounds, “ballooning to almost 1,000 times their minute winter size” and pumping testosterone through the bloodstream with such force that “what had been a mild, occasional itch to sing during the weeks of a springtime stopover on the mudflats of the Yellow Sea would become a constant hormonal compulsion in the Arctic”.

He tells an amazing tale of bar-tailed godwits, some of which make “the longest non-stop migration known” south – up to 7,500 miles from the Arctic to New Zealand in a continuous, feverous flight lasting eight or more days. They gather the strength for it by gorging themselves on marine worms on the tidal flats of the Alaskan peninsula, doubling their weight within two weeks and making themselves “so obese that they jiggle when they walk”. What happens next is nothing short of a superhero comic scene. Digestive organs “shrink and atrophy”. Pectoral muscles, heart and lungs all double in size until the godwit is ready for flight. Code-switching, the alternation between languages or speech patterns that is the most natural survival instinct of so many a human migrant, has nothing on the mechanics of metamorphosis that have evolved across our avian counterparts.

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