Cairns bird lover Sally Sheldon will never forget the first time she watched a mass roost of whimbrels – a type of migratory shorebird – at the mouth of the Barron River.

“Night was falling and over 600 of these birds were gathered together against the mangroves,” she says. “The sound they were making, constantly talking to each other, was deafening.

“They’d flown in on dusk from all points of the compass. At dawn we watched them quietly take off, one group after another. They were gone within minutes.”

Sally and another Cairns bird researcher, Paul Fisk, monitored whimbrels on the southern bank of the Barron River for four years, until 2023.

Paul discovered their nighttime roost in the 1990s – solving a mystery for local birders who’d long seen whimbrels leaving the Cairns Esplanade and mangrove areas from Yorkeys Knob to Yarrabah on dusk.

Whimbrels only huddle together in huge groups, it seems, at night.

“No other migratory shorebird that we know of roosts in such large numbers exclusively at night quite like that,” Sally, who works for Birdlife Australia, says.

“We would see 600 to 800 whimbrels together every night. Two or three decades ago, numbers were higher. Well over 1000 of these birds would come to Cairns. The Barron River seems to be a really important nighttime place for them, where they feel more protected.”

FAR AWAY FROM SHOOTERS

Whimbrels are still shot in large numbers in some parts of the world by recreational hunters and their feeding grounds are shrinking across the globe because of urban and industrial development.

Because of this, the Cairns mudflats and mangroves are becoming increasingly important for them – and about 25 other migratory shorebird species that travel huge distances to spend summer holidays here.

Up to 4000 shorebirds come to Cairns from Russia, Alaska, Mongolia and China each year after their breeding seasons. They spend up to seven months moulting, growing new feathers and, later in their stay, grazing almost non-stop on crabs, worms, shrimps and molluscs, to double their body weight for the long trip home.

Almost two thirds of these birds – 16 species – are listed as threatened.

A NATIONALLY SIGNIFICANT MIGRATORY SHOREBIRD LOCATION

“Cairns is a significant northern area for migratory birds in Australia,’’ Sally says.

“The Esplanade is one of their richest feeding areas. The inlet captures a mixture of fine sediment, creating extensive mangrove areas and intertidal mudflats with rich invertebrate life that you don’t see in many other places.

“It’s really important for these birds that we keep our mangrove estuaries and inter-tidal mudflats healthy.”

Very little is known about whimbrels when they’re in Australia and Sally puts that down to their nocturnal behaviour and their preference to “go solo” while hunting for food in the mangroves during the day.

“Most of the bird monitoring happens in the daytime when species roost together on high tide,’’ she says.

“We’d like to know more about whimbrels – from whether mass roosting at night is common in Australia to how many of the same birds we see each year.”

HOW WE CAN HELP

The best ways to help whimbrels and other migratory shorebirds is to preserve the natural environments they rely on, she says.

“With urban environments like the Cairns Esplanade, that can be a challenge. Even actions like sand replenishment work can affect their habitat because sand washes onto the mudflats and creates a barrier for feeding.

“Simple things we can all do to help are walking on the boardwalk, above the mudflats and the sandier sections of the Cairns Esplanade, and keeping dogs from chasing birds.”

ENDURANCE ATHLETES OF THE BIRD WORLD

• In a lifetime, migratory birds will fly the same distance as to the moon and back.
• They can’t glide or soar – they literally flap their wings the entire journey.
• To help preserve energy, they can fly while shutting down half their brain.