Extreme Birdwatchers Are Counting Albatross From Spaaace
An international team of scientists has, for the first time ever, successfully demonstrated that highest-resolution satellite imagery can be used to survey populations of wild birds from space
The great albatross, a group of large seabirds, are challenging to study because they wander widely around the globe in search of prey, typically touching down only to nest on the most far-flung and inaccessible of oceanic islands. The expense and risk associated with accessing these islands means that some species’ populations are surveyed only once every few decades.
This lack of population information on the great albatross species is a problem because many are endangered, and accurate, up-to-date census data is critical to timely and effective conservation efforts. In their newly-published paper, lead author Peter Fretwell and his colleagues evaluate a new method for assessing these birds’ populations: satellite imagery. In their recently-published paper, Dr. Fretwell and his colleagues report that the birds are clearly visible in the highest-resolution satellite imagery captured from space and can be counted when they are stationary — either incubating eggs or guarding nestlings — on their isolated nesting colonies.
This is the first time that individual birds have been counted from space. Previous studies of terrestrial animals were small pilot projects, whereas Dr. Fretwell and his colleagues counted the entire nesting population of endangered Northern Royal Albatross in a single breeding season.
Satellite remote-sensing of great albatrosses is timely and accurate
The International Union for the Conservation of Nature (IUCN) officially recognizes 22 albatross species, 10 of which are classified as Endangered or Critically Endangered. The remaining species are either Vulnerable or Near Threatened.
In this study, the research team focused their efforts on two species: the Wandering Albatross, Diomedea exulans, and the Northern Royal Albatross, Diomedea sanfordi. They are classified as Vulnerable and Endangered, respectively, due to fishery bycatch, intentional killing, and pollution (especially eating plastics) (ref).
The Wandering Albatross is found all around the Antarctic, with breeding populations on South Georgia island, the Prince Edwards Islands, Iles Kerguelen, Iles Crozet and Macquarie Island, and with an estimated global population of approximately 8360 pairs.
In contrast, the Northern Royal Albatross has a very restricted breeding area that is confined almost exclusively to just three tiny sea-stacks on the fringes of New Zealand’s Chatham Islands archipelago (Figure 1b).
The Northern Royal Albatross is classified as endangered because, in addition to the previously mentioned threats from humans, it has a tiny nesting area, and is experiencing a rapid population decline after a severe cyclone ripped away the soil and nearly all of the vegetation from its breeding sites in 1985 (ref). There is some evidence that this species is undergoing a partial recovery after Bird Life International conducted a census in 2002 and found that the population had increased from an estimated 5200 breeding pairs in 1995 to 5800 breeding pairs. But how is this species doing today?
Now it is possible to answer this question quickly and precisely without risking life and limb, thanks to the WorldView-3 satellite, owned by DigitalGlobe, that was launched in August 2014. This satellite orbits 770 kilometers (478.5 miles) above Earth, collecting full-color images with a resolution of 31 centimeters (12 inches) — which is unquestionably smaller than a nesting albatross, which has a body length of 107–135 centimeters.
To test the accuracy and overall usefulness of WorldView-3 satellite imagery for documenting albatross populations, Dr. Fretwell and his colleagues first counted Wandering Albatross nesting on Bird Island, which is an intensively monitored breeding site near South Georgia island in the southern Atlantic Ocean (Figure 1a). These satellite count data were “ground truthed” with actual ground surveys.
The large bodied, mostly white albatross were were easy to spot in the WordView-3 satellite images. Each bird comprised several white pixels that strongly contrasted against the dark background (Figure 2).
After their successful test run on the Bird Island population of Wandering Albatross, the researchers then used WorldView-3 imagery to document and count endangered Northern Royal Albatross, which nest in similar habitats located in the Chatham Islands archipelago. After examining the images, the team found that Northern Royal Albatross numbers were stable on one island cluster, the Forty-Fours, but had dramatically declined on the Sisters, another cluster of tiny stack-islands in the archipelago.
Closer examination shows that the vegetation cover on the Forty-Fours is good now, but it remains poor on the Sisters. This is consistent with the poor breeding success documented after the 1985 cyclone. Nesting birds remove nearby vegetation to incorporate it into their nest mounds to cushion and insulate eggs and young chicks. The lack of vegetation translates into broken eggs, high nest temperatures and flooding.
Despite the bad news about the nesting population of Northern Royal Albatross on the Sisters, this study demonstrates that satellite imagery could provide a sea change in how we monitor nearly all albatross species. Collecting satellite imagery is relatively inexpensive, fast and is free of the disturbances associated with using drones, airplanes or ground surveys. Of course, clouds do pose a problem, but albatross have an incubation period lasting several months, a time period that generally includes a few cloudless days. Further, satellite imagery could be used to monitor other large, white, surface-nesting birds, such as swans, as well as a wide variety of other wildlife. With luck, perhaps the bird watcher of the future will be able to go birding without stirring from his comfortable armchair, thanks to the wonders of satellite imagery.
Peter T. Fretwell, Paul Scofield, and Richard A. Phillips (2017). Using super-high resolution satellite imagery to census threatened albatrosses, Ibis, published online on 4 May 2017 ahead of print | doi:10.1111/ibi.12482
R.A. Phillips, R. Gales, G.B. Baker, M.C. Double, M. Favero, F. Quintana, M.L. Tasker, H. Weimerskirch, M. Uhart, and A. Wolfaardt (2016). Review: The conservation status and priorities for albatrosses and large petrels, Biological Conservation, 201:169–183 | doi:10.1016/j.biocon.2016.06.017
Originally published at Forbes on 5 May 2017.