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