The study was based on monitoring of 14 petrel burrows on Mauna Loa with digital infrared video cameras in 2007 and 2008. The presence of feral cats was confirmed at eight of the 14 burrows.
Until the cameras were installed, predation by cats was often suspected based on the condition of bird carcasses and presence of cat scat. Predation by cats on live birds was confirmed once the video and still photographs from the infrared cameras were reviewed. In one instance, a cat waited near the entrance of a burrow for more than an hour. When the three-week-old petrel chick emerged, probably to exercise its wings, the cat quickly grabbed it. Remains of the chick were found more than 30 feet from the burrow entrance.
While predation on chicks has an impact on future population growth, predation on adults may be even more serious, says Darcy Hu, natural resources manager with the Hawai`i Volcanoes National Park and one of the study authors.
“This species has delayed sexual maturity, low reproductive potential, and extended nestling development, all of which place a premium on survivorship of the adult birds. Further, the birds also have a high degree of mate fidelity and may have difficulty replacing mates” that have been killed, she said. The authors of the study, “Videographic Evidence of Endangered Species Depredation by Feral Cat” (to be published in Pacific Conservation Biology), write that most of the `ua`u whose remains were recovered had adult plumage and were either breeding or seeking pair-bonds.
One of the methods to limit predation is through construction of a predator-proof fence like the one that now protects Ka`ena Point on O`ahu. At present, the National Park Service is putting up such a barrier around 640 acres on Mauna Loa, protecting nearly four dozen petrel nesting sites. Assisting with the project are the Fish and Wildlife Service and two private groups, the National Fish and Wildlife Foundation and the American Bird Conservancy.
The Hawaiian petrel was once abundant and widespread throughout the archipelago. However, its current population is estimated at just around 15,000 individuals.
Fire Away: The state Department of Land and Natural Resources and its agents are officially free to aerially shoot feral ungulates spotted during helicopter flights over Mauna Kea required under a 1998 U.S. District Court Order to protect the palila (Loxioides bailleui), an endangered Hawaiian honeycreeper.
The Hawai`i County corporation counsel and the state deputy attorney general representing the Department of Land and Natural Resources had recently drafted a stipulated agreement stating that the county would refrain from enforcing its 2012 ban on aerial hunting in cases where the DLNR was conducting hunts in accordance with the court order. But the county prosecutor refused to sign it.
And because of his refusal, U.S. District Judge Michael Seabright found that his court had jurisdiction over the matter and ruled April 8 that the federal order trumps the county ordinance.
Results from a recent palila survey have not yet been released, but Rob Stephens of the DLNR’s Division of Forestry and Wildlife said in Februray that he noticed that the birds are pushing out into new areas, “which to me indicates that their core range is getting bad.”