The male eastern koel is a shy and retiring character, although you'd never guess it from his trademark call.
Experts describe it as a "loud ascending whistle".
Countless light sleepers describe it as "the stuff of nightmares".
But for birdwatching enthusiasts like Grahame Feletti, the red-eyed koel's nocturnal call heralds the blooming, booming months of spring, when places like Belmont Lagoon become a noisome stopping-off point for the species, along with thousands of other migratory birds.
While the koels have flown in all the way from Papua New Guinea and South-East Asia, others arrive from even further afield.
"A number of shorebird species seen occasionally around the lagoon and lake are truly migratory," Mr Feletti said.
"Some fly thousands of kilometres from the Northern Hemisphere to get here."
That's what makes Belmont Lagoon – recently made much more accessible thanks to the Fernleigh Awabakal Shared Track and its spectacular birdwatching platform – such a vital habitat.
"It's a living museum of birdlife," Mr Feletti said.
"Recent studies identify at least 130 native and migratory species using the lagoon."
That makes it one of the most diverse avian hotspots in the Hunter Region.
Some arrive only for short stays to feed and rest, while others will spend months or their entire lives in the thick brush, reeds and trees surrounding the lagoon.
"Only about 15 per cent are commonly seen or heard," Mr Feletti said.
"Others, like the brush bronzewing, pheasant coucal and brown quail are shy ground species. Raptors and cockatoos rove widely over the lagoon to feed, but others, like honeyeaters, use it as part of their south-eastern coastal flyway."
Birdwatchers are expected to converge on the lagoon for Birdlife Australia's annual Aussie Bird Count to be held 20-26 October.
Recognised as Australia's biggest citizen science event, last year's count saw more than 57,000 participants count 4.1 million birds nationwide.
Mr Feletti, an avid member of the Hunter Bird Observers Club, said spring was also a prime opportunity to observe "feeding frenzies" on the lagoon: cormorants, gulls, herons and egrets crowding together to chase schools of tiny fish.
"Black swan numbers also grow steadily from a handful in early September to peaks of 300 in late summer. They move daily from lake to lagoon to feed on algae and weed," he said.
Lake Macquarie City Council Manager Environmental Systems Brendan Callander said everyone in the community shared a custodial role to conserve the lagoon's diverse birdlife and protect its habitats from damage.
"We're so fortunate to have a place that's not only so abundant in wildlife but rich in cultural history, right on our doorstep," he said.
"The Fernleigh Awabakal Shared Track, and in particular its 400m of elevated boardwalk skirting Belmont Lagoon, provide a great opportunity to take it all in and learn more about these amazing animals without leaving a trace."
Mr Feletti said the Hunter Bird Observers Club was preparing an updated guide to birdlife on Belmont Lagoon, featuring photos of the most commonly spotted species.
