Vagrancy could help species chart an escape route in the face of human-induced climate change and widespread habitat destruction, say scientists. Instead of staying put and facing potential extinction, a few lone pioneers can explore new habitats as their old homes become unlivable.
The critically endangered Chinese crested tern, for example, was presumed extinct after it was last spotted in 1937. Then, in 2000, and again a few years later, biologists rediscovered the species at sites in China and Taiwan where it had not bred. before. In 2016, scientists discovered two pairs of Chinese crested terns incubating eggs on an uninhabited island in South Korea. Its small surviving population – only around 50 birds – is still threatened by egg poaching and nest-destroying typhoons. But as one conservation officer noted in 2017, the Korean nesting site “means the future for this species looks brighter now.”
With growing attention to climate change, scientists have highlighted the difficulty of unpacking the role of vagrancy in a species’ adaptation. “You can’t predict when or where a vagrant will show up,” said Lucinda Zawadzki, a zoologist at the University of Oxford. “They are, by nature, rare.”
For her own research, for example, Dr. Zawadzki set up 19 mist nets on Bon Portage Island in Nova Scotia to catch and study as many vagrants as possible. She scored 29 in two years – an impressive return for the subject matter. But she conceded it was a small sample for scientific study.
In the absence of a solid understanding of their pioneer journeys, humans have generally referred to avian wanderers as disoriented or blown away.
“There is this historical narrative around wanderers that they must be lost. They must be hateful. There is something wrong with them,” Dr Zawadzki said.
But in the face of climate change, she says, the opposite may turn out to be true: the ability to explore – or, seen another way, the ability to “get lost” – becomes a huge advantage.
“They are more likely to survive,” she said.