Animal Record Holders

Biggest Egg Ever

The common ostrich is the tallest and heaviest bird alive today. It can grow up to 2.8 metres in height and weigh up to 150 kg, which is 50,000 times heavier than the smallest bird, the bee hummingbird. Unsurprisingly, the eggs that the ostrich lays are the largest produced by any bird. Weighing about 1.4 kg on average – the equivalent of two dozen chicken eggs, or around 3,000 hummingbird eggs – it takes about 50 minutes to soft boil one and over an hour and a half to hard boil. The biggest egg ever, however, was laid by the now-extinct elephant bird, which was even larger than the ostrich and lived on the island of Madagascar.

The Legendary Roc

For many years, the elephant bird was steeped in mystery. Arab folktales are full of references to this gigantic creature, appearing most famously in the saga of Sinbad the Sailor. As told in the Arabian Nights, Sinbad and his crew came across an egg the size of a house, which was accidentally cracked by one of the men. In revenge, the massive bird that laid it, the roc, appeared in the sky, darkening the sun with its wings. It then sank Sinbad’s ship by pelting it with boulders. Tales of Sinbad and the roc were spread by Crusaders returning to Europe from the Holy Lands in the Middle Ages. 

Around 100 years later, the famous 13th-century Venetian explorer Marco Polo travelled through Asia and reached the court of Kublai Khan, the grandson of Genghis Khan. During his travels, Polo heard stories of an immense eagle-like bird called the roc that was capable of killing elephants by picking them up in its gigantic talons and dropping them from a great height. It apparently lived on an island south of Mogadishu, a city on the east coast of Africa (in what we now called Somali) where Chinese merchants went to get ivory. Though Marco Polo did not visit this island himself, he called it Madageiscar in his memoirs – or, as we know it today, Madagascar.

To Marco Polo, the roc was no legend – it was a real animal. He never claimed to have seen this monstrous creature for himself, but he did describe what he asserted to be one of its enormous feathers, which had been sent to Kublai Khan – though this was probably just a withered palm frond. He was also shown two colossal eggs to convince him of the bird’s existence.

If we now fast-forward a few hundred years to the 17th century, the French explorer and later governor of Madagascar, Étienne de Flacourt brought back somewhat more believable reports of a giant bird from that region. He claimed – quite rightly – that it was not a massive eagle, but a flightless ostrich-like bird with a long neck and legs. Flacourt was one of the very few Western people to have recorded reliable knowledge of this bird and he wrote about them frequently.

Enormous Eggs

By the 18th century, Madagascar had been sufficiently explored to establish that no such bird lived there. But a hundred or so years later, physical evidence of the creature was discovered – in the form of enormous eggs. Whereas the shells of most birds’ eggs are paper-thin and easily reduced to powder after the chick inside has hatched, the massive eggs of the elephant bird are not so readily destroyed. So, after each generation of chicks hatched, the broken but firm eggshells were left scattered across the land to accumulate in great numbers. Could one of these eggs have been of the same kind that Marco Polo wondered at over 700 years ago at the court of Kublai Khan? Could they, and the huge birds that laid them, have started the legend of the roc?

Not long after, the bones of the animal that must have laid these eggs were also found. The bones were not fossilised; they obviously came from a creature that had existed until quite recently. Scientists realised that the bones and eggs were remnants of a massive species of flightless bird – ostrich-like just as Étienne de Flacourt had claimed – that must have roamed Madagascar in the not-too-distant past, but which was now very clearly extinct. It was named Aepyornis or, more commonly, the elephant bird – not only because of its great size but also after Polo’s grossly exaggerated assertions that it could lift elephants into the air. (It should be noted here that elephants do not live, and never have lived, on Madagascar.)

We can deduce from the elephant bird’s skeleton that this was probably the largest bird that has ever lived. One variety stood 3 metres tall and weighed up to 730 kg – over four times as much as an ostrich. It wasn’t quite the tallest bird ever, for one or two species of extinct moa from New Zealand reached slightly greater heights, but the elephant bird was certainly much stockier and heavier.

The eggs of the elephant bird, when they were first discovered, were of particular interest because they were the biggest that anyone, then or now, had ever seen. At about the same size and shape as a rugby ball, and with a volume equivalent to that of 160 chicken eggs, they dwarf those laid by the ostrich and are the largest laid by any known animal, dead or alive – larger, even, than the eggs produced by the biggest dinosaurs. It is thought that eggs cannot physically get any larger than this. After all, the greater the volume of an egg, the thicker the shell must be to hold its contents. Most birds develop a small egg tooth on the tip of their beak to help them break free of their eggs, but after a certain shell thickness, they wouldn’t be able to hatch at all.

End of the Elephant Bird

Sadly, it was probably these giant eggs that led the elephant bird to its doom. Recent archaeological evidence suggests that the birds lived alongside humans for hundreds of years, so clearly this wasn’t the usual story of humans finding a new species and then exterminating it within a few decades, as happened with the dodo on the island of Mauritius. But as humans cleared more and more of Madagascar’s forest, there was less room for the elephant birds and less foliage for them to browse on.

It seems likely that people did not hunt the elephant birds for food on a particularly large scale, because very few of the elephant bird bones that we have discovered have cut marks on them, which would indicate the place where humans cut the flesh away from the bone with a knife. Indeed, humans may have had difficulty tackling an adult elephant bird, for it would undoubtedly have been a very formidable opponent.

But they could take its eggs, which were a huge source of nourishment and could feed several people at once. So although several factors probably threatened the elephant bird’s survival, including habitat loss, it is likely that people eating their massive eggs – the largest the world has known – is what dealt this species its final blow.

To find out more about bird eggs in general, make sure you read our accompanying article, which can be found here. For other Easter-related goodness, check out our British Wildlife of the Week posts on the European rabbit and the brown hare.