What makes this stretch of the Cooper so rich is, paradoxically, what it lacks. The floodplain below Windorah has no deep, fast channels to drain it. Instead the water disperses into a fine, complex web of small-scale drainage lines that hold it in place, keeping the plain inundated for months after the flood peak has passed. That slow release is the secret of the place. A flood here does not surge through and vanish in days; it lingers, evaporating and seeping at the lazy pace the flat clay dictates, long enough for plants to grow, for fish and crustaceans to multiply, and for chicks to hatch and fledge. Vegetation grades from low forbs, grasses and sedges to tall tussock grass and dense thickets of legumes, with swamps of bluebush, lignum and belalie. The scattered waterholes are ringed by lignum, belalie and coolibahs. It is a landscape engineered by its own flatness to soak up a flood and dole it out slowly, exactly the conditions that breeding waterbirds need.

The numbers are staggering. During the floods of 2004, this floodplain was estimated to support around 200,000 waterbirds. BirdLife International recognises it as an Important Bird Area precisely because of events like that one, when the plain held more than one percent of the entire world populations of straw-necked ibis, glossy ibis and white-headed stilt at once. These are not regional tallies but global ones, concentrated onto a single desert floodplain. Aerial surveyors counting from low-flying aircraft tallied tens of thousands of birds directly and estimated the rest in colonies too dense to enumerate from above. For a place that is bone-dry most of the time, the abundance is almost unbelievable.

The roll call reads like a survey of inland Australia's waterbirds. Great egrets nested here in their thousands during the 2004 flood, alongside royal and yellow-billed spoonbills sweeping the shallows. Grey teal, pink-eared duck and plumed whistling duck rafted across the water in the thousands. Whiskered terns hawked overhead, black-tailed native-hens scuttled through the lignum, and brolgas, those tall grey dancing cranes, stalked the margins. The plain draws rarities too: the elusive grey falcon, the stately Australian bustard, and the small, secretive Bourke's parrot have all been recorded here. Each flood assembles this cast anew, drawn from across a continent to a feast that may not come again for years.

Major floods reach this plain only about once every five years, and that irregular pulse is the whole logic of the system. The waterbirds of arid Australia are nomads and opportunists, sweeping in to breed explosively when the water arrives and dispersing when it dries. Sites like the Cooper Floodplain below Windorah are the rare, vast nurseries that make the boom possible, the places where a single good flood can launch a generation of birds. Lying within the Lake Eyre Basin, one of the last great unregulated river systems on Earth, this floodplain still runs on nothing but rain and gravity. Protect the flood, and you protect the spectacle: a desert that, every few years, fills with water and wings.