Ikigai Daily
Menu
WonderEvolution fact

Darwin's finches, more than a dozen bird species of the Galápagos Islands, all descend from a single ancestor. Their beaks range from thick nutcrackers for hard seeds to fine tweezers for insects, each suited to the food on its island.

Galápagos Islands

EvolutionBiologyScienceNature

The story behind the card

Darwin collected some of these birds in 1835 during the voyage of HMS Beagle but did not realise at the time how closely related they were; the ornithologist John Gould pointed it out after the voyage. Today they are a textbook case of adaptive radiation, in which one ancestral species splits into many, each suited to a different way of life. Despite the name, they are not true finches but belong to the tanager family. Since 1973 Peter and Rosemary Grant have studied them on the small island of Daphne Major. After a severe drought in 1977 left mostly large, hard seeds, birds with bigger beaks survived better, and the next generation's beaks were measurably larger: evolution seen within a few years.

Türkçe oku
Darwin ispinozları, Galápagos Adaları'nda yaşayan on ikiden fazla kuş türüdür ve hepsi tek bir atadan gelir. Gagaları, sert tohum kıran kalın gagalardan böcek toplayan cımbız gibi ince gagalara kadar çeşitlenmiştir; her türün gagası yaşadığı adadaki besine uygundur.
Galápagos Adaları

Darwin bu kuşların bir kısmını 1835'te HMS Beagle yolculuğu sırasında topladı, ama birbirlerine ne kadar yakın akraba olduklarını o zaman fark etmedi. Bunu yolculuktan sonra kuşbilimci John Gould ortaya koydu. Bugün bu ispinozlar, biyolojide adaptif radyasyon denen olgunun ders kitabı örneğidir: Tek bir atadan gelen tür zamanla çoğalır ve her yeni tür farklı bir yaşam biçimine uyum sağlar. Adları yanıltıcıdır; aslında gerçek ispinoz değil, tangaragiller familyasındandırlar. Peter ve Rosemary Grant 1973'ten beri bu kuşları küçük Daphne Major adasında inceliyor. 1977'deki şiddetli kuraklıktan sonra geriye çoğunlukla iri ve sert tohumlar kalınca büyük gagalı kuşlar daha çok hayatta kaldı; sonraki kuşağın gagaları ölçülebilir biçimde daha büyüktü. Evrim, birkaç yıl içinde gözle izlenebilmişti.

Sources and further reading

Background reading: Darwin's finches
Get the mobile appAbout our cards

Related cards

These cards share a subject or reading mode with the card above.

WonderNature

Welwitschia, a plant of the Namib Desert in Namibia and Angola, grows only two leaves in its whole life. They keep growing from their base for centuries, and some plants are thought to be more than a thousand years old.

The Austrian botanist Friedrich Welwitsch came across the plant in southern Angola in 1859; he wrote that he knelt and gazed at it, half afraid that touching it would prove it imaginary. It is a gymnosperm, like conifers, which means its seeds form in cones rather than inside fruit, and male and female cones grow on separate plants. Over the years the wind tears the two leaves into many ribbons, so an old plant looks like a heap of leaves. The Namib is one of the driest places on Earth. The leaves catch fog and dew, which drip onto shallow roots, although a 2019 study suggests that rain soaking into the ground is its main water source. The plant appears on Namibia's coat of arms.

WelwitschiaRead card
WonderNature

The kākāpō, a flightless, night-active parrot of New Zealand, courts with sound: in the rare years when it breeds, males dig shallow bowls in the ground and boom from them through the night, a deep call that can carry for more than a kilometre.

The kākāpō is the world's only flightless parrot and the heaviest, with males weighing up to about 4 kilograms. It once lived across New Zealand, but hunting and the dogs and rats brought by Polynesian settlers, then the cats, stoats and rats that came with Europeans, drove it close to extinction. Today every surviving bird has a name and lives on predator-free islands or in fenced sanctuaries, watched over by the Kākāpō Recovery programme. Females breed only in years when rimu and some other native trees produce a huge crop of fruit, known as masting, which comes every two to four years. In those seasons rangers check nests closely and sometimes raise chicks by hand.

KākāpōRead card
WonderNature

Rafflesia arnoldii lives almost entirely inside a tropical vine as a parasite, emerging briefly to produce a vast carrion-scented flower.

Rafflesia arnoldii grows in the rainforests of Sumatra and Borneo. It is named after Sir Stamford Raffles and the surgeon and naturalist Joseph Arnold, who recorded it in Sumatra in 1818; local people knew it long before. It is a holoparasite: it has no green tissue at all and takes all its water and food from its host, a Tetrastigma vine of the grape family, living as threads of cells inside the vine's stem. A bud swells for many months before opening into a flower up to about a metre across and weighing several kilograms, the largest single flower of any plant. Its smell of rotting meat draws the carrion flies that pollinate it, and the bloom lasts only about a week. Several Rafflesia species are threatened as forests are cleared.

Rafflesia arnoldiiRead card
WonderNature

The hooded pitohui, a songbird of New Guinea, can carry batrachotoxin, a nerve poison also found in some poison frogs, in its skin and feathers. Levels vary from bird to bird and are thought to come from its diet.

People in New Guinea have long known the bird is unpleasant to eat, and Western naturalists recorded this as early as 1895; 'pitohui' is said to be a Papuan term for 'rubbish bird'. Its poison drew scientific attention in 1990, when researchers preparing the birds' skins for museum collections felt numbness and burning in their hands. In 1992 a team including the ornithologist Jack Dumbacher reported homobatrachotoxin, a close relative of batrachotoxin, in the skin and feathers, making pitohuis among the first poisonous birds documented by science. The likely source was later traced to small Choresine beetles, found in pitohuis' stomachs and carrying the same family of toxins. The poison probably helps deter predators and parasites such as feather lice.

Hooded pitohuiRead card
WonderEvolution

In Hawaii, silverswords, shrubs, cushion plants, vines and trees all descend from a single tarweed, a sticky plant of the daisy family from North America's Pacific coast, that reached the islands millions of years ago.

The ancestor belonged to the tarweeds, sticky, resinous relatives of sunflowers that grow along the Pacific coast of North America. DNA studies suggest it reached Kauaʻi about five million years ago, perhaps as a seed caught in a bird's feathers. With few competitors, its descendants spread into dry scrub, wet forest, bogs and bare lava fields, and today about 34 species in three genera make up what botanists call the silversword alliance. The best known, the silverswords themselves, form globes of silvery, sword-shaped leaves on the high volcanic slopes of Maui and Hawaiʻi Island; some species flower only once, sending up a tall stalk of flower heads before dying. Many members are now endangered, chiefly by grazing animals and invasive plants brought by people.

Silversword allianceRead card
Next card in the archiveEastern monarch butterflies fly up to 4,800 kilometres from Canada and the United States to the mountains of central Mexico each autumn, yet no single butterfly makes the whole round trip: the yearly cycle takes about four generations.Read next →