In the lush rainforests of Australia, birds roost in the low branches and amble across the forest floor, enjoying the shade and tropical fruits. But the jungle isn’t theirs alone. A dingo is prowling in the shadows, and fruit won’t satisfy his appetite.
鬱鬱蔥蔥的澳洲雨林內 小鳥棲息在低矮的樹枝上 在林地穿梭漫步 享受著樹蔭及熱帶水果 但是這片叢林並不專屬於牠們 一隻澳洲野犬在陰影中潛行覓食 而水果不能滿足牠的胃口
The birds flee to safety all but the cassowary, who can’t clear the ground on her puny wings. Instead, she attacks, sending the dingo running for cover with one swipe of her razor-sharp toe claws.
眾鳥逃往安全地 除了食火雞 牠小小的翅膀幫不了牠逃命 相反的,牠攻擊! 用鋒利的爪子一揮 就讓小野犬跑去找掩護
The cassowary is one of approximately 60 living species of flightless birds. These earthbound avians live all over the world, from the Australian outback to the African savanna to Antarctic shores. They include some species of duck and all species of penguin, secretive swamp dwellers and speedy ostriches, giant emus, and tiny kiwis.
食火雞是大約六十種 不會飛的鳥類之一 這些束縛於地上的禽類 生活在世界各地 從澳洲內陸 到非洲草原,到南極海岸都有 包括某些種類的鴨子 以及所有種類的企鵝 躲躲藏藏的沼澤居民 和飛奔的鴕鳥、巨大的鴯鶓
Though the common ancestor of all modern birds could fly, many different bird species have independently lost their flight. Flight can have incredible benefits, especially for escaping predators, hunting, and traveling long distances. But it also has high costs: it consumes huge amounts of energy and limits body size and weight. A bird that doesn’t fly conserves energy, so it may be able to survive on a scarcer or less nutrient-rich food source than one that flies. The Takahe of New Zealand, for example, lives almost entirely on the soft base of alpine grasses. For birds that nest or feed on the ground, this predisposition to flightlessness can be even stronger.
及微小的奇異鳥都是 雖然所有現代鳥類的共同祖先都會飛 很多不同的鳥類都分別 失去飛行能力 飛行可以帶來很多不可思議的好處 特別是逃避掠食者、獵食 且能長距離旅行 但是飛行也有極高的代價: 它需要消耗極大的能量 體型及體重也都受限 不會飛的鳥可以節省能量 所以牠比會飛的鳥更能在食物稀少 或食物營養較差的狀態下生存 以紐西蘭的南秧雞為例 幾乎全部生活在 高山草原的柔軟基底 對在地面築巢或覓食的鳥類而言 這種不會飛的傾向 更加強烈
When a bird species doesn’t face specific pressures to fly, it can stop flying in as quickly as a few generations. Then, over thousands or millions of years, the birds’ bodies change to match this new behavior. Their bones, once hollow to minimize weight, become dense. Their sturdy feathers turn to fluff. Their wings shrink, and in some cases disappear entirely. And the keel-like protrusion on their sternums, where the flight muscles attach, shrinks or disappears, except in penguins, who repurpose their flight muscles and keels for swimming.
如果某種鳥類不用面對 一定要飛的特定壓力 牠就會停止飛行 只要幾代就會失去這種能力 然後,在數千或數百萬年後 鳥類的身體就會改變 以配合這種新行為 牠們原本要減輕重量而中空的骨頭 會變密 牠們強健的羽毛會變鬆軟 牠們的翅膀萎縮 某些例子甚至完全消失 而胸骨上的龍骨狀突起 即飛行肌肉連接之處 也會萎縮或消失 除了企鵝 牠們的飛行肌肉及龍骨有另外的用途
Most often, flightlessness evolves after a bird species flies to an island where there are no predators. As long as these predator-free circumstances last, the birds thrive, but they are vulnerable to changes in their environment. For instance, human settlers bring dogs, cats, and stowaway rodents to islands. These animals often prey on flightless birds and can drive them to extinction. In New Zealand, stoats introduced by European settlers have threatened many native species of flightless bird. Some have gone extinct while others are endangered. So in spite of the energy-saving advantages of flightlessness, many flightless bird species have only a short run before going the way of the dodo.
就是為了游泳 最常見的是,鳥類失去飛行能力 是因為飛到某個島 而島上沒有掠食者才演化出來的 只要這種沒有掠食者的情況持續下去 鳥類就繁衍興旺 但牠們很容易受到環境變化的影響 舉例來說,人類移民帶著狗 貓及偷偷跟來的鼠類到島嶼上 這些動物經常捕食不會飛的鳥 也可能使牠們滅絕 在紐西蘭,由歐洲移民帶來的白鼬 已經威脅到許多不會飛的原生鳥種 有些已經絕種,有些則瀕臨絕種 所以儘管不會飛有節省能量的好處 許多不會飛的鳥都撐不了太久 就像渡渡鳥一樣絕種了 但是有少數幾種不會飛的鳥
But a few flightless birds have survived on mainlands alongside predators aplenty. Unlike most small flightless species that come and go quickly, these giants have been flightless for tens of millions of years. Their ancestors appeared around the same time as the first small mammals, and they were probably able to survive because they were evolving— and growing—at the same time as their mammalian predators. Most of these birds, like emus and ostriches, ballooned in size, weighing hundreds of pounds more than wings can lift. Their legs grew thick, their feet sturdy, and newly developed thigh muscles turned them into formidable runners.
在掠食者眾的大陸上存活下來 不像大多數小型不會飛的鳥種 來得快去得也快 這些大型鳥已經數千萬年不會飛了 牠們的先代出現的時間 大約與第一批小型哺乳類相同 牠們之所以能存活下來 是因為牠們演化 同時也長大! 就像掠食牠們的哺乳類一樣 大多數這些鳥,如鴯鶓及鴕鳥 體型像吹氣球一樣長大 比牠們的翅膀能承受的 還重好幾百磅 牠們的腿變粗,腳變結實 而新發展出來的大腿肌肉 讓牠們成為飛毛腿
Though they no longer use them to fly, many of these birds repurpose their wings for other means. They can be spotted tucking their heads beneath them for warmth, flashing them at prospective mates, sheltering eggs with them, or even using them to steer as they charge across the plains. They may be flightless, but they’re still winging it.
雖然牠們不再用翅膀飛行 這些鳥讓翅膀 產生新的用途 牠們常被看到把頭塞進翅膀下取暖 揮舞著翅膀求偶 用翅膀保護蛋 甚至在草原上飛奔時用它們控制身體 牠們可能不會飛 但還是會展翅