As dusk fell over Australia's Phillip Island last week, thousands of tiny black-and-white birds participated in the largest "penguin parade" seen on the island since record-keeping began in the 1960s, with more than 5,200 little penguins (Eudyptula minor) crossing the beach in a single night.

Phillip Island — known as Millowl to the Indigenous Bunurong people — hosts Australia's largest colony of little penguins, which is currently about 40,000 birds strong, according to the Penguin Foundation, a group that funds research and conservation efforts on the island. This is the world's smallest penguin species; the birds grow to be no bigger than about 15.7 inches (40 centimeters) tall, or about the height of a bowling pin, according to The Australian Museum.

Every day at dusk, a subset of the Philip Island penguin population swims back to shore after hunting for fish, squid, krill and small crustaceans in the ocean, and then heads inland toward their nesting grounds. This event, locally known as the "Penguin Parade," draws large numbers of tourists to Phillip Island Nature Parks, where visitors can "sit and watch the penguins emerge from the water for 50 minutes" each night, Paula Wasiak, a Phillip Island Nature Parks field researcher, told Live Science in an email.

"Penguin viewing has occurred at the same location for over 50 years and the birds have been habituated to nightly activity over time," she said. (If you can't make it to the island in person, you can also watch livestreams of the parade on Facebook or YouTube.)

At dusk on May 3, an unusually large number of penguins took part in the parade, as 5,219 little penguins stormed the shore at once and then took off toward their burrows.

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"We couldn’t believe our eyes when more than 5,000 penguins came out of the water in less than an hour," Wasiak said in a statement.

To count the birds, park rangers station themselves at the four main penguin "highways" — dedicated paths that the wee birds always use to come ashore, Wasiak told Live Science. "Little penguins cross in groups, with the same penguins using the same pathway each time they enter the colony," and throughout the 50 minute parade, rangers count every bird that waddles down these paths, she said.

The record for the island's largest penguin parade had just been broken the previous week, on April 29, when 4,592 birds came ashore at once, Wasiak told Live Science. The prior record was set on a November night in 2021, when 4,435 birds scuttled across the sand and toward their nests, according to ABC Gippsland, a local news station owned by the Australian Broadcasting Corporation.

Overall, May's parades have included surprisingly high numbers of penguins, with approximately 3,000 to 5,000 birds marching each night. "It’s been a penguin party night after night, which is unusual for this time of year, let alone in record numbers like we are seeing now," Wasiak said in the statement. Historically, the largest parades have taken place in November and December, at the peak of the birds' breeding season, according to the Penguin Foundation.

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Why have this month's penguin parades swelled to such remarkable sizes? It may be that this year's La Niña event — where strong trade winds sweep across the Pacific, from South America to Indonesia — may be boosting the birds' offshore food supply, which means that more birds are congregating in coastal waters rather than seeking food farther away.

Little penguins primarily feed on small fish, such as anchovies, which can only survive in a narrow temperature range, Wasiak told Live Science. "It suggests that during La Niña years, the ocean conditions around Phillip Island are often ideal for an abundant supply of fish/food close to the shore," she said.

Typically, when they're not breeding, the penguins can spend up to a month foraging at sea, Wasiak told ABC Gippsland. With food closer to shore, the penguins instead make quick turnaround trips and arrive back on the beach just in time for the nightly parade.

On top of the prolonged La Niña event, the high parade attendance may be related to a phenomenon known as the "autumn breeding attempt," where older penguins in the colony attempt to breed outside of peak mating season, Wasiak told Live Science. This breeding attempt is usually preceded by an uptick in the number of penguins heading out to forage.

May's large parades may also be a result of steady improvements in the penguins' island habitat, Wasiak told Live Science.

"One of the main areas we're seeing an increase in penguin attendance is to the east of the colony. In the past, poor habitat and erosion in this area meant penguins had difficulty accessing and nesting there," Wasiak said in the Parks' statement. "A lot of work has gone into improving dune structure, creating penguin pathways and restoring habitat, which is now paying off."

Originally published on Live Science.