The migratory shorebirds

Twice a year a stretch of this coast’s mud turns into one of the most important petrol stations on Earth. The flats laid bare at every low tide look, to us, grey, wet and lifeless. They teem with buried life: worms, crabs and molluscs, the rich harvest of the sediment and rotting leaf the estuary traps. That larder is why, every year, a crowd of travellers arrives from the far side of the world to work it. They are the migratory shorebirds, and the one that beggars belief is the bar-tailed godwit.

The godwit breeds in the short Arctic summer of Alaska and Siberia, then flies south to spend the rest of the year feeding on flats like these. Part of that trip sounds made up. It flies non-stop, out over open ocean, for many days and many thousands of kilometres, never once stopping to rest, drink or feed. The verified records are hard to read with a straight face. Tagged godwits have flown well over eleven thousand kilometres in a single unbroken flight (Gill et al. 2009), and one young bird tracked in 2022 crossed from Alaska to Tasmania, some thirteen and a half thousand kilometres, in eleven days without setting down once. It is the longest non-stop flight known of any bird: an animal the weight of a small parcel, burning its own body for fuel over an ocean with nowhere to land.

A flight like that only works if the bird can gorge itself beforehand and refuel hard at the other end. A godwit finishes its crossing burnt down to almost nothing and has to eat its way back to strength before it can breed again. The flyway it rides, the East Asian-Australasian Flyway, is a chain of such fuel stops running from the Arctic down to Australasia, and the flats of this coast and the wider Moreton Bay are one of its links. That is not a turn of phrase. A migrant on a journey of that scale cannot simply feed somewhere else; the good flats are rare, they lie far apart, and each is a link the bird is fuelled and timed to reach. Pull out one and a chain that reaches halfway around the globe breaks, and the birds that leaned on it arrive with nothing left to burn: the shorebirds that depended most on the Yellow Sea’s vanishing mudflats are the ones that have declined fastest (Studds et al. 2017).

Not all of them cross the ocean in one heroic leap. The largest of these travellers, the eastern curlew, works the same flats differently, stalking the mud on long legs and probing it with a preposterous down-curved bill, the better part of a hand-span of it, shaped to reach down a crab’s burrow and draw it out. It too breeds in the far north and spends the rest of the year on flats like these, and it has become a grim barometer of their health. As the mudflats of the flyway have been drained, walled and built over, the eastern curlew has declined so steeply that it is now listed as critically endangered, a bird sliding toward extinction one reclaimed estuary at a time.

So the wider Moreton Bay is recognised as a Ramsar wetland, listed in 1993, largely for these birds. Read this stretch of tidal country the way you would read the rest of the estuary: as ground doing specific, irreplaceable work, not spare land waiting to be improved. Its worth has nothing to do with how it looks at low tide and everything to do with where it sits in a chain that runs to the Arctic. That chain is already shedding links. Pave a flat and you cannot put it back.