Using images from ESA’s Copernicus Sentinel-2 satellite, a team of researchers from the British Antarctic Survey has spotted 8 new colonies of emperor penguins (Aptenodytes forsteri) and confirmed the discovery of three previously identified but never confirmed breeding sites. This discovery, described in a paper in the journal Remote Sensing in Ecology and Conservation, takes the global census to 61 colonies around the entire continent.
Emperor penguins are high latitude, ice obligate seabirds that breed during the austral winter. They feed mainly upon fish, krill and cephalopods, mainly within the pack ice, in leads or polynyas.
They are highly adapted to cold conditions and spend their entire lives in the Antarctic. Almost all their colonies depend upon stable sea ice, which they use as breeding habitat.
They arrive at their preferred breeding sites in late March-April, and lay eggs from May to June. Eggs hatch after 65 days and chicks fledge from December to January.
Thus their breeding habitat, land-fast ice, must remain stable for approximately 9 months.
In February to March, adults haul out to molt, possibly traveling long distances — up to 1,200 km (746 miles) — from their breeding sites to areas of seasonally persistent pack ice where they may remain for several weeks.
Studying emperor penguin colonies is extremely difficult. Nevertheless, over the past decade, scientists at the British Antarctic Survey have been able to search for new colonies using satellite imagery.
Although penguins are too small to show up in satellite images, giant stains on the ice from penguin droppings — known as guano — are easy to identify at the 10 m (33 feet) pixel resolution that the Copernicus Sentinel-2 mission offers.
These brownish patches have allowed the team to locate and track penguin populations across the entire continent.
“This is an exciting discovery,” said study lead author Dr. Peter Fretwell, a geographer at the British Antarctic Survey.
“The new satellite images of Antarctica’s coastline have enabled us to find these new colonies.”
“And whilst this is good news, the colonies are small and so only take the overall population count up by 5-10% to just over half a million penguins or around 265,500-278,500 breeding pairs.”
Most of the newly-found colonies are situated at the margins of the emperor penguins’ breeding range. Therefore, these locations are likely to be lost as the climate warms.
“Whilst it’s good news that we’ve found these new colonies, the breeding sites are all in locations where recent model projections suggest emperors will decline,” said co-author Dr. Phil Trathan, Head of Conservation Biology at the British Antarctic Survey.
“Birds in these sites are therefore probably the ‘canaries in the coalmine’ — we need to watch these sites carefully as climate change will affect this region.”
The study found a number of colonies located far offshore, situated on sea ice that has formed around icebergs that had grounded in shallow water.
These colonies, up to 180 km (112 miles) offshore, are a surprising new finding in the behavior of this increasingly well-known species.
Peter T. Fretwell Philip N. Trathan. Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins. Remote Sensing in Ecology and Conservation, published online August 4, 2020; doi: 10.1002/rse2.176