The avian world has some amazing nest builders. Bald eagles build enormous aeries made of sticks. Bower birds decorate theirs with bling, whilst the pouch-like nests of penduline tits are so strong it’s said they have been used as children’s shoes.
The biggest bird nest in the world, however, is a collaborative effort, constructed and maintained by a single species, the sociable weaver (Philetairus socius) from southern Africa.
- It weighed more than 2 tonnes and holds the record for the largest bird nest in the world
- This whopping, record-breaking wasp's nest was 7 metres long – that's bigger than a Cadillac – and found inside a house
Think of it less like a conventional nest, and more like an apartment block. Each structure contains hundreds of individual chambers, which are each home to a single pair of birds and their brood.
Constructed in trees and sometimes around telegraph poles, each structure can be up to six metres across. Each block can contain hundreds of nesting chambers, and up to 500 birds. This fact earns the birds another accolade. Sociable weavers also produce the most densely populated bird nests in the world.
This sandy-coloured, sparrow-sized bird has a black chin, barred flanks and a scalloped back. They live in the arid savanna regions of South Africa, Namibia and Botswana, where they build with local materials.
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The body of the nest is made from dried grass, which gives the structure its distinctive haystack-like appearance. Large twigs are used to create the roof, spiky bits of straw are used to protect the entrance holes, whilst cotton, fur and other soft items are used to line the chambers.
Each nest is inhabited by multiple generations of weavers who contribute to its upkeep. They constantly repair and add to the structure, but not all birds contribute equally. A study in the journal PLOS ONE found that some individuals spend more time primping their personal chambers and less time adding to the outer, communal thatch. This ‘selfish’ behaviour does not go unnoticed. Birds who are team-players act aggressively towards them, which prompts the mavericks to behave more co-operatively.
Successful nests can be extended across decades, and last for more than 100 years. With new material continuously added to old, the enormous structures can weigh up to 1000 kilograms, which earns the birds another accolade. The sociable weaver also makes the heaviest bird nest in the world. Nests sometimes become so weighty that they topple the trees they sit in.
Sociable weaver nests also provide habitat for lots of other species. Paradise finches and rosy-faced lovebirds use their chambers for breeding. Ashy tits and pygmy falcons bag cells for roosting. Spotted eagle-owls nest on top of the structure. Skinks hide within, whilst mammals, such as cheetahs, kudu and jackals use the nest trees for shade, rest and sometimes for vantage points.
This means that the nests of the sociable weaver create year-round biodiversity hotspots, and whilst there might not be a Guinness Record for that, there should be!
