Feather map reveals secrets of waterbirds

Pristine plumage may secure waterbirds an audience, but it’s the atomic detail in their feathers that could one day help protect their homes.

A team of Australian scientists is using nuclear techniques to analyse waterbird feathers and create a “feather map” that tracks bird movements. The research, they hope, will help water managers ensure the birds stay healthy and their habitats are protected.

Wetlands in Australia are under pressure from drought, river regulation, climate change and changes to land use. It is estimated that only half of what existed prior to European settlement remains.

The straw-necked ibis, along with other birds that breed in colonies and nest only in wetlands, has been struggling with the stress and populations are in decline.

Waterbirds congregate in large numbers at known breeding wetlands when they become flooded, but where they fly off to in the meantime has been a mystery. Australian waterbird feathers being sent to Kate Brandis at the University of New South Wales (UNSW) are set to change that.

“Feathers are made of keratin which, once it’s formed, doesn’t change again,” Brandis explains. “So feathers create a record of what the birds have been eating and drinking, which is specific to where they are in the landscape.”

Part of a citizen science project, members of the public are being asked to collect feathers from different wetlands around Australia and mail them to Brandis, who will analyse them with colleagues at the Australian Nuclear Science and Technology Organisation (ANSTO) and UNSW.

First, Brandis’ team will probe the feathers’ elements by bombarding a sample with high-energy X-rays. These rays are absorbed and emitted, or “fluoresced”, as wavelengths that are characteristic of different elements. Each feather will be scanned to reveal the ratios of up to 28 different elements, which vary in different soils.

“The elements are tied to the geology and the soil of a region and we know they vary greatly across the country,” Brandis explains.

Waterbirds incorporate elements from the soil into their feathers through the plants and insects they eat. Brandis found in a pilot study that calcium, potassium and sulfur levels in bird feathers vary the most between a subset of wetlands.

But identifying elements alone is not enough to give away the birds’ location. For more data, Brandis’ team will analyse each feather’s stable isotopes of oxygen, hydrogen, nitrogen and carbon.

Isotopes are different forms of the same element – they contain the same number of protons but a different number of neutrons at the centre of the atom. Carbon, for instance, comes in two stable forms, carbon-12 and carbon-13.

Birds ingest different oxygen and hydrogen isotopes through the water they drink, and carbon and nitrogen isotopes through proteins in their food. Brandis’ team will study each feather sample in a mass spectrometer, where a detector counts how many atoms of the different isotopes are present.

The ratios of these isotopes are characteristic of different wetlands in Australia.

In a 2010 pilot study, Brandis showed this by comparing the elements and isotopes in chick feathers from three different wetland sites that had become breeding hotspots for colonial waterbirds after the Murray-Darling Basin flooded.

And analysing feathers is not just useful for tracking the elusive waterbirds. They “can also give us a bit more information on the health of the wetland and the diet of Australian birds,” Brandis says.

Brandis will combine this element and isotope data to create her Feather Map, where feathers collected from chicks and birds that don’t travel long distances will provide a reference “signature” for the wetland each feather was collected from. The feathers of birds that do travel long distances, such as the straw-necked ibis which moves between wetland habitats, can then be matched to these signatures based on their own elements and isotopes.

Brandis hopes her map will help inform policymakers’ and water managers’ decisions about water flow to ensure waterbird habitats are conserved.

“We can make sure that the population is kept healthy, so that when breeding opportunities do arise, they’re in a fit state to breed,” says Brandis.

Although Brandis has already received thousands of feathers, the researchers need many more.

To learn how you can get involved, visit www.ansto.gov.au/feathermap