Phys.org reports that the female population of the endangered Hawai’i creeper is only 22 to 28 percent of the remaining adult population in the southern portion of the Hakalau Forest National Wildlife Refuge. The numbers come from research performed by University of Hawai’i at Mānoa scientists Leonard Freed and Rebecca Cann and raise concerns that the number of females is becoming too low to maintain the species over the long term.
From 2001 to 2007, Hawai’i creeper population declined by 63 percent throughout a 3,400-hectare open forest area at Hakalau Refuge on the windward slope of Mauna Kea, according to trend analyses by Freed and Cann. The scientists observed the male-biased sex ratio along the elevation gradient in a formerly high density section of the forest, including a closed forest area study site that is considered more pristine, and found that it was associated with the population decline in the refuge’s open forest areas. Hakalau formerly had the best population of creepers on the island.
The main threat to the creeper is the non-native Japanese white-eye, which is out-competing the creeper for food.
By 2006 to 2007, Freed and Cann found that the white-eye was replacing the creeper throughout both the disturbed and the pristine areas of the refuge…
“We know the creeper is in serious trouble, and we urgently need to increase adult female survival,” Freed said. “At a minimum, this will include controlling Japanese white-eyes. Also, captive breeding may be necessary to produce females that can be released into the wild to restore the adult sex ratio.”