The migratory shorebirds

Twice a year a piece of this coast's mud becomes one of the most important petrol stations on Earth. The mudflats and sandflats laid bare at every low tide look, to us, like the very definition of empty — grey, glistening, lifeless — and are in fact dense with buried life: worms, crabs, molluscs, the harvest of all the sediment and rotting leaf the estuary traps. That buried food is why, every year, a crowd of travellers arrives from the far side of the planet to work it. They are the migratory shorebirds, and the greatest of them, for sheer disbelief, is the bar-tailed godwit.

The godwit breeds in the brief Arctic summer of Alaska and Siberia, then flies south to spend the rest of the year on flats like these — and it makes part of that journey in a way that ought not to be possible. It flies non-stop, over open ocean, for many days and many thousands of kilometres, without once landing to rest, drink or feed. The verified records are almost hard to read with a straight face: individual satellite-tagged godwits have flown well over 11,000 kilometres in a single unbroken flight, and one young bird tracked in 2022 crossed from Alaska to Tasmania — about 13,560 kilometres — in roughly eleven days without setting down once. It is the longest known non-stop flight of any bird, an animal the weight of a small parcel burning its own body as fuel over an ocean with no islands to fall back on.

Here is where the flats stop being scenery and become a matter of life and death, and where this reads as a lesson in dependence (see species-dependence). A flight like that is only survivable if the bird can fatten enormously beforehand and refuel hard at the far end — a godwit arrives at its wintering grounds burnt down to almost nothing and must eat its way back to strength before it can breed again. The flyway it travels, the East Asian–Australasian Flyway, is a chain of such refuelling stations strung down the globe from the Arctic to Australasia, and the intertidal flats of this coast and the wider Moreton Bay are one of its links. That is not a figure of speech. A migrant on a journey of that scale cannot simply feed "somewhere else"; the productive flats are rare, they are far apart, and each one is a rung the bird is timed and fuelled to reach. Pull out a rung and you do not inconvenience a bird — you break a chain strung halfway around the planet, and the birds that depended on that link arrive at an empty tank with nowhere to fill it.

This is exactly why the flats are read the way the rest of the estuary is read (see estuarine-zonation): as a band that does specific, irreplaceable work, not as spare ground waiting to be improved. It is also why the wider Moreton Bay is recognised internationally as a Ramsar wetland — listed in 1993 — precisely for its migratory shorebirds. The unremarkable-looking mud is, to a godwit, the thing that makes the impossible journey possible. And the flyway is already losing links: as the flats of Asia and Australia are drained, walled and built over, the birds that lean on them are sliding, the largest of them, the eastern curlew, all the way to critically endangered. Every flat left standing on this coast is a piece of a lifeline, and its value is set not by how it looks at low tide but by where it sits in a chain that reaches to the Arctic.