January
22, 2019, American
Ornithological Society
The two
seabird species unique to Hawaii, Newell's Shearwaters and Hawaiian Petrels,
are the focus of major conservation efforts—at risk from habitat degradation,
invasive predators, and other threats, their populations plummeted 94% and 78%
respectively between 1993 and 2013. However, a new study in The Condor:
Ornithological Applications offers hope of previously undetected colonies
of these birds on the island of Oahu, from which they were believed to have
vanished by the late 1700s.
Shearwaters
and petrels nest colonially in crevices, burrows, and under vegetation at mid
to high elevations. They
currently breed on other Hawaiian islands including Kauai
and Maui, but were both believed to have extirpated from Oahu prior to European
contact in 1778; biologists believed that occasional records from the island
were birds thrown off-course at night by city lights.
Pacific
Rim Conservation's Lindsay Young and her colleagues used a spatial model based
on elevation, forest cover, and
illumination to identify potential suitable breeding habitat for both species
on Oahu, then deployed automated acoustic recording units at 16 sites on the
island to listen for the birds' calls in 2016 and 2017, accessing remote
mountain locations via helicopter. To their surprise, they detected petrels at
one site and shearwaters at two sites.
"We
were doing a statewide survey for these species for the U.S. Fish and Wildlife
Service as part of recovery action planning, but Oahu was not initially
included as one of the sites to survey, since evidence suggested they weren't
there," says Young. "Since we're Oahu-based, we thought we would at
least put a few recording units out to see if there was anything. And we were
surprised, to say the least, that we not only had calls detected, but detected
both species across two years."
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