Where do our gentoo penguins go in winter?

26/06/2025

BAS marine ecologist Professor Phil Trathan sheds light on how the gentoo penguins of Goudier Island spend their polar night.

Gentoos are the only species of penguins that breed at Port Lockroy on Goudier Island. They are known as brushtail penguins because of their long sweeping tails, and are the third largest penguin species, following the emperor and king. They are closely related to Adélies and chinstraps (also brushtail penguins) but have distinctive orange-red bills and feet. 

When it comes to the austral summer, we’re pretty much experts on how the world’s most famous penguins spend their time. Every year, we send a team to the base to run the world’s southernmost post office and museum there. We’ve been surveying the colony at Port Lockroy since 1996. It has run every year except 2020/21, when the base was closed due to the pandemic.

Penguin counting at Port Lockroy in 2024 (Credit: Laura Büllesbach/UKAHT)

However, during the eight months or so, from March to October, when we’re not around, and the polar night rolls in, we’re not so certain what the waddling little acrobats get up to. Therefore, we’ve enlisted the help of Professor Phil Trathan, marine ecologist with the British Antarctic Survey, to shed some light on how the gentoo penguins of Goudier Island spend their winter.

A bustling summer 

In the summer, Port Lockroy is a busy place, with approximately 600 breeding pairs of gentoo penguins. There are also usually other gentoos that are either too young to breed (gentoos first breed at age three or four) or have tried to breed but failed. 

Once breeding is complete and all the chicks have fledged, gentoos leave the colony to feed and recover their body condition lost during the seven or eight weeks of chick rearing. Port Lockroy is quiet, but not for long, as the birds later reassemble for their annual moult.  

Unlike many birds, penguins undergo a ‘catastrophic moult’, during which they replace all their feathers. New feathers grow and push out the old ones, making the penguins appear dishevelled and scruffy. 

A gentoo undergoing ‘catastrophic moult’ (UKAHT/Jérôme Viard) 

Moult usually takes around 20 days, during which the penguins can’t feed. Because moulting uses up so much energy, penguins can lose up to three per cent of their body mass each day. At the end, with their new plumage, the birds look sleek and polished, although their new brushtails have not quite grown and will only do so slowly over the next few weeks.

Leaving for winter 

Once their moult is done, the gentoos leave for the winter, and Goudier Island falls silent. The days shorten and the temperatures drop. Winter sea ice increases, and most other seabirds begin to depart the area, but not the gentoos. They are unusual in comparison to other Antarctic seabirds in that they do not migrate to warmer regions further up the Peninsula, but generally remain in the vicinity of their breeding sites. They may relocate a few hundred kilometres, but generally they will stay close to home.

Gentoos feed on crustaceans, fish and squid (UKAHT/Kirsty Dick)

Gentoo penguins must continue to find sufficient food during the short days of winter. As visual predators, finding enough food during winter is a challenge, with less than four hours of daylight on Midwinter Day (21 June). During the long, dark nights, gentoo penguins often seek safety by hauling out onto land. 

After the solstice, the days lengthen until the Port Lockroy team’s arrival in November. By then, there are over 17 hours of daylight and never total darkness. They are greeted by gentoo pairs returning to their nesting sites as Goudier Island teems with activity and noise once more. 

Twilight on Goudier Island, time for the gentoos to leave for the winter (UKAHT/Jérôme Viard) 

Adopt a penguin 

Thanks to our penguin adopters, we were delighted to send Maggie Coll to monitor the wildlife at Port Lockroy this season.

Gentoo penguins are climate change winners, and their populations are increasing. Warmer winters have allowed them to expand their range southwards. Their broad diet of crustaceans, fish and squid means they can prosper where other penguins can’t. 

However, they face threats from avian flu and commercial krill fisheries. In 2022, heavy snowfall also buried the penguins’ pebble nests, delaying their breeding season. 

Monitoring on the island provides important information to guide policy to protect the penguins, not only on Port Lockroy, but elsewhere in the Antarctic.    

Please consider adopting one of our Port Lockroy penguins, either for yourself or as a gift for someone special. 

Your support enables the team at Port Lockroy to monitor and protect the gentoo penguin population. Your gift will include a soft toy, certificate, fact booklet, e-updates and even a postcard from Antarctica! 

Professor Phil Trathan is a marine ecologist with the British Antarctic Survey. He has participated in 20 Antarctic field trips. You can learn more about his work on the British Antarctic Survey website.