A foul-smelling oasis in outback Australia is providing a crucial refuelling stop for migratory birds born in the Arctic Circle.

Key points: The Alice Springs Sewage Ponds has emerged as a popular pit stop for hungry migrating birds

The Alice Springs Sewage Ponds has emerged as a popular pit stop for hungry migrating birds The nutrient-rich ponds offer birds fuel for their transcontinental journeys

The nutrient-rich ponds offer birds fuel for their transcontinental journeys Artificial wetlands like the sewage ponds are also becoming increasingly vital for native bird species

These birds fly from Mongolia, western Alaska and Siberia to Australia each year, with many relying on outback sewage ponds to survive the 13,000 kilometre journey.

About two million migratory shorebirds visit Australia every year, and most of the 37 species are under threat.

Through contributing data on migratory bird populations, research and conservation organisation Birdlife Central Australia is beginning to grasp the significance of this unlikely safe haven.

"Conserving habitat that these birds need to fuel their incredible migrations is an international challenge," said Bird Life Central Australia's Lisa Nunn.

"This means artificial wetlands like the Alice Springs Sewage Ponds are becoming increasingly important."

The Alice Springs Sewage Ponds has become a pit-stop for migratory birds. ( ABC News: Hamish Harty )

Many of the migratory birds fly the journey, referred to as the East Asian-Australasian Flyway, twice each a year in search of an endless summer.

"They want to avoid winter, [so] they come down here for our summer and then they go back to the northern latitudes for a brief summer there," Ms Nunn said.

The parents fly first, leaving their eight-week-old offspring to fly alone.

Ms Nunn said this is an enormous feat, given the young fly solo to Australia.

"The journey itself is incredibly taxing on the body," she said.

"When they're feeding, their digestive organs are all enlarged so they can take in as much food as possible. And then when they go to leave, those organs shrink and their heart expands.

"When they arrive in Australia their reserves are really depleted, and the birds are really skinny. Often, they're really on the cusp of life and death."

The congregation of birds like the pied stilt has become a must-see for bird watchers. ( Supplied: Peter Nunn )

World-class bird watching 'biological hazard'

Bird watchers from all over the world flock to the 14 Alice Springs Sewage Ponds to witness the international bird pit stop.

"Sharp-tailed sandpipers tend to be the most common; we've counted up to 190 on site at one time," Ms Nunn said.

There's plenty on offer in the ponds for birds like the curlew sandpiper. ( Supplied: Peter Nunn )

Other migratory waders that regularly visit the sewage ponds include the wood sandpiper, common sandpiper, marsh sandpiper, common greenshank, red-necked stint and long-toed stint.

The birds feed on tiny invertebrates in the nutrient-rich waters.

"Most of them will stop half way to refuel, and by the time they leave the Arctic … about 55 per cent of their body is fat and they'll burn that at an extraordinary rate," Ms Nunn said.

"They might fly three days non-stop, they'll stop in eastern Asia and they're quite skinny by that time and they'll then build up their fat reserves again to make their way to Australia."

Coping in the drought

The sewage ponds also provide a vital permanent water source for local native birds in the area.

"We've seen a definite decline in the amount of bird life we're seeing out bush," Ms Nunn said.

"A lot of birds have started coming into town because there is so little food and water out bush."

Even common Central Australian birds have been flocking to the ponds due the lack of rain and river beds drying up in the region.

Many birds on the East Asian-Australasian Flyway flock to soak up Australia's summer. ( Supplied: Lisa Nunn )

"Birds of prey are congregating at the ponds because there is always food for them there, regardless of the surrounding conditions," Ms Nunn said.

"We regularly see black kites, whistling kites, wedge-tailed eagles, peregrine falcons and black falcons hunting. This week we even saw a swamp harrier, a very uncommon species in the desert."

Despite the dangers of the waste water treatment ponds to humans, Ms Nunn said it did not harm the birds.

"It doesn't seem to have done them any harm by now; we've had a few migratory birds that have overwintered here for several years, so I assume it's working out for them very well," she said.