An anxious build-up to the big journey north
Experienced shorebird migration watchers call it the ‘zugunruhe’. And when they see it, they know it won’t be long before one of nature’s great journeys begins.
Zugunruhe is a German word that describes the anxious behaviour of migratory animals – particularly birds – as they prepare to depart for their traditional breeding grounds.
Roebuck Bay, just to the south-east of Broome in Western Australia, is one of the best places in the world to observe the beginning of the annual wading bird migration from Australasia to the Arctic.
Between 4.00 and 6.00pm most evenings through March, a small group of dedicated observers occupies the same spot on the orange pindan cliffs overlooking the eastern end of Roebuck Bay. (They choose that time because most birds migrate late in the day and at night, when they are less vulnerable to predators and flying conditions are usually more settled.)
The watchers are mostly associated with the nearby Broome Bird Observatory (BBO) and they record the identity and exact size of each flock, and precisely when they passed overhead. All vitally important information for tracking the birds up and down the East Asian-Australasian Flyway.
But this is not just an exercise in statistics. Many of these people are professional researchers and birding experts who go to extraordinary lengths to keep tabs on these globally threatened world travellers.
Migratory shorebirds have been coming and going from the food-rich mudflats of Roebuck Bay for aeons. And being right there when the first birds respond to the primeval call to head north is a special experience – even for ‘hardened’ observers.
Tall and bespectacled John Graff is a former assistant warden at the BBO. One of the best birders I have ever met, he is a little shy around people. But when it comes to the birds there are no such inhibitions.
“Even for me, the departure is emotional,” he confessed as we rattled over a heavily corrugated dirt road running parallel to the bay. “Especially knowing what they are about to do.
“The eastern curlews that flew over our heads last night will still be flying now (mid-afternoon), and still be flying [non-stop] in two days’ time. It is an enormous feat of endurance for them and they have to beat their wings the whole time.”
So how do you know you are seeing the zugunruhe?
“[At Roebuck Bay] you need a relatively low tide and good expanse of exposed mud. A lot of the birds will be wandering around feeding and doing their own thing. But if you see birds roughly lined up and all facing north, they won’t be feeding,” says John.
Different species adopt different spacing while on the ground: eastern curlews often spread out while the knots form compact lines. “Eventually, the odd bird will jump up, flap its wings and maybe even take off and do a little exploratory flight, and land again. That’s what we call ‘zugunruhe’. And when you see that you know they are likely to leave that night … but not always!”
On my most recent visit to Roebuck Bay, a flock of about 40 eastern curlews led the migration to their breeding grounds in Mongolia, quickly followed by greater sand-plovers.
“If you’re lucky enough to see them leave they will take off, gradually gain height and eventually form a rough V and head over [the wader watchers’ heads],” says John
“Sometimes they will return, and you start putting human emotions into the process, like: Do they have the courage to go? Nervousness, perhaps. And when a flock keeps returning, the numbers steadily grow as other birds decide to join them”.
The size of the bird has nothing to do with the sequence of species departures. They have to wait until their breeding grounds up to 12,000 km away are free from ice and snow.
The more southerly breeders like the eastern curlew and the sand plovers will leave first, and the last to go will be the red knots and ruddy turnstones, which breed right up in the New Siberian Islands.
©Tony Neilson, Natural Images 2018