The Melanesian megapode has a naked face, often with red or pink coloration. It uses hot volcanic sand to incubate its eggs – an ancient behaviour now found in only a handful of bird species. THE LAVA BIRDS Meet the megapodes – ground-dwelling birds that start life beneath the sand. By Mark Cocker Photos David Tipling

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Clockwise from left: Megapodes excavate their nest chambers; these 550g birds can dig to impressive depths; there can sometimes be a bit of a skirmish among the birds, as they look for suitable digging spots; volcanically heated sand results in communal nest grounds; Savo Island.

he sound of our boat’s New Guinea, as far as southern Australia, to a beach bordering the forest, where the engine drowned out the vast then way out into the central Pacific through megapodes lay. The locals make these sand- silence of the South Pacific the array of islands known as Melanesia. fields even more attractive for the birds by night. It was 4am and pitch Savo is among that complex of archipelagos clearing fallen debris, while a thatched fence black – the only thing I and it is no coincidence that this spot, like around the perimeter excludes predators, could see distinctly was the much of the zone in which megapodes occur, such as pigs, dogs and monitor lizards. whiteness of the breakers experiences some of the highest levels of Even as we took our seats behind the ‘blind’ Tcrashing and spreading onto the shore. seismic activity known on Earth. we could hear the megapodes in the trees We were on the Solomon Islands, at a Savo is a live volcano and the megapodes overhead, where they produced a loud, place called Savo, to see a bird that lays have probably exploited the island’s high-pitched chorus of ‘yee-yeeow’ notes. its eggs in the ground, like a crocodile. subterranean heat to incubate their eggs The embryos are warmed by the heat of for millennia. In turn, the local people have Beach burrowers volcanoes. When they hatch, the chicks, learned to exploit this relationship to supply Local tradition has it that Savo’s birds alone and unaided, have to scramble up themselves with some of the most nutritious come from Guadalcanal, the largest of at this point that those remarkable feet As it goes deeper, a megapode has the parts in their mouths or tongues that help – sometimes through 1.5m of sand – from eggs produced by any avian species. the Solomon Islands, about 15km to the came into their own. Finding a suitable challenge of removing the spoil that has them judge the substrate’s temperature. the nest-grave in which their mothers We were still in semi-darkness when south. In truth, they probably come from spot, a bird would set to raking hard and, accumulated at the mouth of its hole. The naturally occurring heat vent slowly have buried them. Parent and offspring Wilfred Ngasi, the chief of Agatoka village, all directions and many islands, since sites in less than a minute, could go from full It must routinely emerge to clear these incubates the egg and the chick emerges will never knowingly meet. ushered me and photographer David Tipling with the necessary geothermal conditions view to vanishing completely into its tailings before returning to the ‘coal-face’. about 50 days later. In some species The creature in question is called the are exceptional. There is one Melanesian own excavations. The scene was one of of megapode, such as the Australian Melanesian megapode – a ground-dwelling megapode nesting ground called Pokili, on astonishing industry accompanied by a Hidden depths malleefowl, eggs have hatched after species, about the size of a chicken, with In less than a minute, the island of New Britain, that drew in an relentless hubbub of high contact notes. Later in the day, we were present when 90 days. For comparison, the average a small head, short brown wings and a estimated 53,000 birds in a single season The megapodes undertook adjacent local people dug out the resulting cavities domestic chicken takes fewer than 30. spherical body that carries a deep, dark blue- a megapode would during the 1970s. Such is the importance diggings and pulsing jets of scraped and it was astonishing to see the depths to The family, as a whole, uses two other black sheen. Its most notable feature is the of these spots that, in the past, people sand would fly into the air in sequence. which this 550g bird had descended. I even methods of incubation aside from making size of its legs and feet, which explain that go from full view to fought running battles over control of Each excavation proceeded in a rhythmic attempted to retrieve one of these eggs and the most of geothermal activity. Three odd name – megapode means ‘big foot’. them, sometimes with fatal consequences. pattern but often with the spoil arcing in vanished head-first into a burrow with only species use beaches that are warmed simply Megapodes form a separate ancient family vanishing into its At Savo, the neighbouring villagers diametrically opposed directions. Several my feet showing. by the sun, but the most common strategy called the Megapodiidae that includes 22 regulate their megapode fields amicably. birds would occasionally be busy all in one It was intriguing to find that the bottom is to exploit heat generated by the microbial species, which occur from the Indian Ocean own excavations. Soon the birds were running freely across patch, but out of sight, and it would appear of the hole was moist and warm; it is decomposition of vegetation. Melanesian across parts of Indonesia, the Philippines and them to begin their morning’s work. It was as if the ground were magically digging itself. thought that megapodes possess sensitive megapodes also use this method.

34 BBC Wildlife June 2019 June 2019 BBC Wildlife 35 MEGAPODES Some of the best egg-finders were often bathed in sweat from their exertions.

Brush-turkeys are viewed as pests in suburban areas. Talking turkey: Australia’s industrious megapodes

Perhaps the best known of all mounds. They even take megapodes is the Australian over compost heaps for brush-turkey. It bucks the nests. Yet the prize winner downward population trend for industry is undoubtedly common among the family the scrubfowl. Some and, in parts of suburban mounds, which are probably Queensland, even has ‘pest’ communal and used over status. Birds regularly block several generations, have up gardens with heaps been measured at 51m of rotting leaves and will in circumference and 8m incorporate footballs, cans high, with an estimated and silver spoons into their 50 tonnes of vegetation.

Yet 12 other species gather together rotting it hatches. Melanesian megapode eggs are Seventy-year-old Wilfred recalled his bird family’s wider range – with inevitable vegetable debris, using their super-sized feet 100g, roughly twice the weight of a chicken childhood days when megapodes continued consequences. Megapodes are now on a as rakes. They build it up into mounds in egg and about a fifth of the mother’s own to come to lay eggs in these fields all day. survival frontline and about 30 species which to deposit their eggs. This behaviour weight. But the yolk content compared Sometimes they were so numerous and of the family are thought to have been is practised by what are probably the best to that of a chicken is at least four times so eager to reach the site that they would wiped out already in the last 1,000 years. known of the family, the trio that are higher, making it far more nutritious. fly into people on the beach. But, now, like Of today’s 22 species, 12 are considered found widely in Australia – the scrubfowl, Humans have valued the birds as almost everywhere else in the megapode’s at some risk of extinction. Mercifully, the malleefowl and Australian brush-turkey. precious resources for thousands of years range, Savo’s human population has Melanesian megapode is still a bird to be The natural assumption is that the birds and little has changed today on Savo. Once increased while the birds have declined. found in abundance, but for how long? inherited their incubation strategies directly the megapodes had finished their morning’s The traditional nest sites found right from some reptilian ancestor. Yet this is now labours, it was the turn of the villagers, who Striking a balance across this region once gave rise to a thought not to be the case. Rather, the first harvest the eggs as food but also as a kind The old sustainable system, which ensured wonderful symbiosis. Humans kept out representatives of the family used normal of currency, each one representing about 10 the nest grounds were left undisturbed to let predators and supervised the sand-fields, avian incubation methods – that is, their Solomon Island dollars (£1). megapodes breed successfully for some of so that they met the megapodes’ breeding own body heat – but subsequently evolved It’s one thing to marvel at the industry of the season, has all ended. Though the locals requirements. In return, the people were their unique alternatives. the birds, but it was almost as impressive to practise a modicum of restraint, leaving a blessed with an unending source of Any similarities between megapode and see how the locals probed the blank canvas tiny patch nearest to the village delicious eggs. What is required is the will crocodile behaviour are thought to be a of the sand, located the as a supposed harvest-free to restore that sustainable partnership. It result of convergent evolution – the process filled-in burrows and zone, it looked completely would be nothing short of tragedy to lose by which unrelated species independently dug down precisely to unsuitable for megapodes the birds that lay these golden eggs. evolve the same solution to one of life’s where the eggs lay. It and there was no evidence problems. It is also assumed that the family was no less arduous that they ever used it. MARK COCKER is a naturalist and Clockwise from off to protect developed the mound technique first, and than it was skilful Throughout the rest of writer. His latest book is Our Place here: stout legs megapodes; locals then shifted later to digging burrows. and some of the best the fields, the goal was to (Jonathan Cape, £18.99). and large feet dig up the species’ A striking aspect of the family’s biology egg-finders were find and take all the eggs. are adapted eggs, which are FIND OUT MORE for digging highly sought is the size of the egg and its yolk, which often bathed in What happens on Savo Learn more about the and scraping; after; humans have supplies all those nutrients that enable a sweat from their recurs almost Solomon Islands, home to Melanesian nesting grounds waged battle for chick to be self-sufficient from the moment exertions. everywhere in this megapodes: visitsolomons.com.sb are fenced- the birds’ eggs. June 2019 June 2019 BBC Wildlife 37