With its pink, willowy legs and appetite for venturing onto new terrain, the Hawaiian stilt, or ae’o, seems particularly poised to take on climate change.
As rising seas and urban development threaten the bird’s natural wetland habitat, new scientific research suggests the endangered species is moving inland to neighborhoods and industrial zones — and it seems to be managing there just fine.
The early signs of habitat adaptability could make the indigenous Hawaiian stilt particularly resilient to climate change, which is expected to dramatically reshape the coastal regions where the bird has historically reigned.
Other native waterbirds, such as the Hawaiian gallinule, or`alae`ula, and the Hawaiian coot, or ʻalae kea, have not shown such signs of habitat versatility.
But as the Hawaiian stilt increasingly moves out of its protected wetland habitat onto soccer fields, golf courses, neighborhood lawns, public parks and wastewater treatment plants, it faces new threats from humans, pollution and predators, including dogs, rats, mongooses and feral cats.
“Management really only occurs within wetlands,” said Martha Kawasaki, a graduate student at the University of Hawaii Hilo who presented her research on the citified bird at the Hawaii Convention Center on Wednesday during the state’s 26th Hawaii Conservation Conference. “But we need to kind of think about this differently, because this is actually a highly mobile species and they use habitats outside of their wetlands and they’ve expanded into our urban areas.”
Elegant and slender, the foot-tall Hawaiian stilt is typically found in shallow waters, grassy fields or exposed tidal flats on all the main Hawaiian Islands except for Kahoolawe.
Only flamingos have longer legs in proportion to their body size.
In the late 1940s, there were about 1,000 Hawaiian stilts in the islands. But their numbers have not increased much, according to the U.S. Fish & Wildlife Service.
On Oahu, home of the state’s largest Hawaiian stilt population, most of the species reside in wetlands and ponds on the north and Windward coasts, according to the state Department of Land and Natural Resources. It is known to spend time in fresh, salt or brackish water.
“They are protectors and pillars of the wetlands,” Kawasaki said. “They announce visitors and they announce the dawn. If you’ve ever been to a Hawaiian wetland you can hear and see this.”
But as wetland habitats grow scarce — Oahu has already lost an estimated 65% of its wetlands — the Hawaiian stilt has been increasingly spotted by researchers and residents in upland terrain populated by humans.
In 2017, Kawasaki and her research team — ecology researcher Eben Paxton of the U.S. Geological Survey Pacific Island Ecosystem Research Center and UH Hilo biology professor Patrick Hart — caught four Hawaiian stilts on Oahu and set out to trace their movements through various habitat types.
They affixed solar satellite tags to each bird. The tags recorded a GPS location every 90 minutes from 4 a.m. to 8 p.m.
The study marked the first time birds in Hawaii have been tracked using that technology, Kawasaki said.
Three of the birds were tracked from July 2017 to February 2018, while one bird, whose GPS tracker broke, was tracked only until October 2017.
The results revealed what the researchers already knew anecdotally: The Hawaiian silt is spending less time in wetlands and more time in developed areas.
One bird spent most of her time in her Pearl Harbor wetland habitat and a small amount of time in an adjacent soccer field. Another spent about half his time on the grounds of a wastewater treatment plant and much of the rest of his time in a nearby urban setting.
The other two spent time in all four habitat zones, with the majority of time spent in wetlands and fields cleared for future development.
All four birds tended to spend the night in their wetland habitat and venture out into more developed upland areas between dawn and dusk.
Kawasaki and her colleagues did not observe the birds’ behavior as they moved between habitats during the study period.
Kawasaki said she would like to study whether foraging for food or some other activities are propelling them to venture into historically new terrain.
“They are showing some resilience to climate change, which is great,” Kawasaki said. “But that also brings additional exposures to threats.”
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