Scientists counting albatrosses from space
IN A WORLD-FIRST, New Zealand and British scientists are using high-resolution satellite images to count birds and provide accurate estimates of their population.
Scientists at the British Antarctic Survey and the Canterbury Museum in New Zealand used satellite imagery from the WorldView-3 satellite – a commercial Earth-observation satellite launched in August 2014 – to assess the population density of endangered albatrosses.
Albatrosses are rare and, because of the remote locations of their habitats, they are also relatively hard to survey and study.
“Often the islands where these birds breed are hundreds, sometimes thousands of kilometres from the nearest airstrip, so survey by aircraft is difficult. Some colonies have to be surveyed by small boat, which is also challenging and can cause potential disturbance to the birds,” said Dr Peter Fretwell, a remote sensing expert from the British Antarctic Survey.
WorldView-3 satellite image snapshots of the Chatham Islands from February 2016 showing white dots assumed to be Northern Royal Albatrosses.
“The populations of some of these important breeding sites have not been assessed for 30 years or more due to these problems,” added Peter, who led the new study, which is published in the journal Ibis.
Now, thanks to the availability of high-resolution satellite imagery, Peter and his team were able to literally spot individual albatrosses in the photos and accurately assess their populations.
The team developed and tested the accuracy of the new method by counting individuals on a well-studied colony of wandering albatross (Diomedea exulans) on South Georgia, then applied it to the northern royal albatross (Diomedea sanfordi), a species that only breeds in New Zealand.
“The ability to count them accurately by satellite gives us a really useful tool which will aid conservation efforts to save these beautiful endangered birds,” Peter said.
“We can take satellite imagery at any time of year of any place no matter how far away it is.”
While this new method offers clear advantages over traditional approaches to counting individuals, there are some drawbacks, commented Barry Baker, a marine biologist from the Institute for Marine and Antarctic Studies at the University of Tasmania.
“The limitations to the method are that at this stage the resolution of the imagery precludes using the technique for small albatrosses and other seabirds, or larger species that are not predominantly white,” he said. “It also can’t be used on nesting colonies that aren’t on relatively flat terrain.”
Also, despite the increased resolution of the satellite imagery, the birds appear like tiny white dots, which may sometime be misleading – rocks can sometime be mistaken for birds, or vice versa, said Peter.
Caveats aside, Peter thinks this new technique will prove helpful for assessing the population status of these endangered species.
“We are already working with a number of NGOs to implement satellite counts of many albatross colonies, especially the ones that are in the remotest areas or those that have not been counted for decades to get robust population assessments,” he said.