Elephant birds were flightless giants found only on Madagascar, and they died out about a thousand years ago. The largest stood about 3 m tall with the head raised, and their eggs are the largest known from any bird, reptile or mammal. Their closest living relatives are the kiwis of New Zealand. The name refers only to size.
Who holds the record
Calling an elephant bird the largest bird ever rests on weights that differ by more than three times. From the girth of the thigh bone, Hansford and Turvey in 2018 calculated a mean of 409.5 kg for Aepyornis maximus and 642.9 kg for an even bigger form, with one incomplete femur reaching 860 kg, the largest known bird individual, they say. On comparable data the Australian thunderbird Dromornis averaged 583.6 kg for males. From eggshell, Grealy and colleagues estimated about 1 000 kg for the layer of the thickest eggs, with a margin of more than 400 kg. Hume and Walters gave A. maximus about 275 kg.
Hansford and Turvey warn that all these numbers lie outside the range of the living birds used to build the equation. Dromornis stirtoni remains a contender, and “possibly the largest” is as far as the evidence goes.
Aepyornis, and the short life of Vorombe
Geoffroy Saint-Hilaire described Aepyornis maximus in 1851 from bones and eggs, and 15 species had been named by 1934. Hansford and Turvey measured collections worldwide and cut the list to four species in three genera: Mullerornis modestus, Aepyornis hildebrandti, Aepyornis maximus and, for the largest bones, the new genus Vorombe, Malagasy for “big bird”, with the species name titan from Andrews in 1894.
DNA soon challenged that. Grealy and colleagues gathered more than 960 eggshell fragments from 291 localities and recovered 17 near-complete mitochondrial genomes. They found no genetic sign of a separate genus: one bone identified as probable Vorombe and one as probable A. maximus were identical at the gene compared. They suggest the two are one species with much larger females, as in kiwis, where females can reach 120 to 180 per cent the size of males. That would make the record-holder a female A. maximus. Sexing the bones with nuclear DNA is still needed to confirm it, though some authors already treat Vorombe as a synonym.
The same study argued that Mullerornis needs a family of its own and found a separate Aepyornis lineage in the far north, at about 230 kg.
Eggs that crossed an ocean
The eggs were 26 to 40 cm long and held 5.6 to 13 litres, about 160 times the volume of a hen’s egg. The thickest shells average 3.32 mm, and Grealy estimates such eggs weighed about 10.5 kg. Two whole eggs of A. maximus have turned up in dunes in Western Australia, thought to have floated there from Madagascar. In 1658 Flacourt, a French governor, wrote of an ostrich-like bird, the vouron patra, that laid eggs like an ostrich.
Such giant size may be recent: Grealy and colleagues estimate that the common ancestor of Aepyornis, about 1.4 million years ago, weighed about half as much as A. maximus.
A giant that may not have seen much
Aepyornis had a long neck, small head, straight conical bill, vestigial wings and very stout legs, with no sign of a fourth toe or spur. Torres and Clarke reconstructed their brains in 2018 and found very small optic lobes, almost absent in the larger species, like those of kiwis. That points to a nocturnal bird, perhaps blind. Large olfactory bulbs in A. maximus suggest a forest life guided by smell. Isotopes show mostly browsers, except A. hildebrandti of the central highlands, which ate up to about 48 per cent grass.
Cut marks and a sudden end
In 2018 Hansford and colleagues reported chop and cut marks on bones from Christmas River dated to 10 721 to 10 511 years ago, which would put people on Madagascar more than 6 000 years earlier than other evidence. The claim is controversial: the oldest securely dated evidence of people is from the middle of the first millennium AD.
Either way, people and elephant birds overlapped for centuries at least. A 2021 study with 30 new dates found that elephant birds and hippos persisted across much of Madagascar until about 1 200 to 900 years ago, then collapsed suddenly. The collapse matches the conversion of forest to grassland around 1 100 to 1 000 years ago, probably linked to a shift to farming and herding. Direct evidence of hunting is limited.
