By Sara Rigby

Published: Monday, 25 October 2021 at 12:00 am

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When you think of the world’s biggest species, you probably think of mammals – giraffes, elephants, blue whales. Birds are comparatively small, at least in the UK. Here, you’re more likely to see a robin or a sparrow than something that weighs tens of kilograms.

But bird species can be surprisingly large, with the very largest even taller than a human.

Even these species have nothing on the extinct elephant bird. The species Vorombe titan, which lived in Madagascar over 1,000 years ago, may have weighed up to 800kg.

10. Dwarf cassowary

Maximum weight: 17.6kg

Distribution: New Guinea

Living in forests on hills and mountains up to 3km high, Casuarius bennetti is the smallest of the three species of cassowary. Over a metre long, this bird feeds on fungi, fruit, and even insects or small animals.

9. Mute swan

Maximum weight: 22.5kg

Distribution: Central and Northern Europe; Central and Eastern Asia

Despite its name, the mute swan (Cygnus olor) is a vocal bird, though its voice is quieter than other species and it only uses it occasionally. They are usually found in lowland freshwater marshes, lagoons and rivers.

8. Lesser rhea

Maximum weight: 25kg

Distribution: Argentina, Bolivia, Chile and Peru

Rhea pennata is also known as Darwin’s rhea, after the naturalist studied the species on his second voyage on the Beagle. Though Darwin struggled in his search for the bird, he was successful after the artist Conrad Martens, who joined him on the voyage, shot and prepared one for dinner.

7. Greater rhea

Maximum weight: Over 25kg

Distribution: Argentina, Bolivia, Brazil, Paraguay, and Uruguay

This grassland-dwelling species, Rhea americana, is omnivorous. As well as plants, it likes to eat grasshoppers, lizards, frogs, small birds and some snakes.

6. Emperor penguin

Maximum weight: 46kg

Distribution: Antarctica

This iconic species can stand as tall as 115cm and weigh up to 46kg. Aptenodytes forsteri will trek up to 120km over ice to reach a breeding colony.

5. Emu

Maximum weight: 55kg

Distribution: Australia

Of the four surviving members of the family Casuariidae, three are cassowaries, and the fourth is the emu. Adult emus can stand at 190cm tall, and though they weigh on average between 30 and 45kg, the largest reach 55kg.

4. Northern cassowary

Maximum weight: 58kg

Distribution: New Guinea

Like other species of cassowary, Casuarius unappendiculatus is a flightless bird. After being laid by a female, the eggs of this species are incubated by a male who raises them for nine months.

3. Southern cassowary

Maximum weight: 58kg

Distribution: New Guinea and Queensland, Australia

The southern cassowary (Casuarius casuarius) is only slightly larger than its cousin, the northern cassowary. They live in rainforests, swamp forests and savannah woodland, and can grow up to 170cm in length.

2. Somali ostrich

Maximum weight: 105kg

Distribution: Horn of Africa

Once believed to be a subspecies of the common ostrich, Struthio molybdophanes was confirmed as a separate species in 2014.

1. Common ostrich

Maximum weight: 156kg

Distribution: Savannahs of Africa

Males of the species Struthio camelus can reach a whopping 2.75 tall. These flightless birds are incredible runners, and can reach speeds of 70km/h (43mph) in a sprint.

Read more:

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• Top 10: Earth’s smallest mammals
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• Top 10: Which animals have the strongest bite?

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