ALAKAI — Small and aloof, the Puaiohi songbirds of Kauai might stand only a few inches high but they have a big impact on their home ecosystem on the island’s Alakai Plateau.
They’re one of the larger of Kauai’s endemic songbirds by size, but the species numbers at less than 500 individuals and it’s the only native songbird species left that distributes fruited plants through Kauai’s area.
That’s according to new research from the Kauai Forest Bird Recovery Project’s Lisa “Cali” Crampton and study co-authors Liba Pejchar and Monica Kaushik, who looked at the role of the Puaiohi, otherwise known as the Small Kauai Thrush, in Kauai’s native ecosystem.
“Kauai has experienced extinction and catastrophic declines in fruit-eating native bird species, combined with the introduction of non-native species. This is the only native songbird capable of dispersing larger seeds in the rainforest,” Crampton said. “Our results underscore how important it is to protect Puaiohi if we want preserve Kauai’s montane ecosystem.”
Puaiohi eat native plant species like ‘olapa, lapalapa, ‘ohi’a ha, kanawao, ohelo, pa’iniu, pukiawe, kawa’u and pilo, and some introduced plants, like thimbleberry, according to Kauai Forest Bird Recovery Project.
They also eat invertebrates.
Kauai has lost five of its native birds in recent decades and those that survive are restricted to a small area of pristine forest at higher elevations. They are at risk from introduced predators, such as rats and feral cats, avian malaria, and habitat destruction, according to the Department of Land and Natural Resources.
“KFBRP works hard to protect Kauai’s forest birds despite a perfect storm of disease, invasive predators, and limited resources to address these challenges; our results reinforce the critical importance of their efforts not only for the birds, but also for Kauai’s diverse and beautiful rainforest,” said Pejchar.
While honeycreepers, another endangered forest bird species on the island, are highly sensitive to mosquito borne illnesses like avian malaria, the Puaiohi are less susceptible. But the birds are still only seen at elevations at which temperatures are too cool for mosquitoes.
“We don’t know exactly why that is, because they used to be found at lower elevations, but is likely related to habitat loss and degradation,” Crampton said.
She continued: “Rat predation seems to be the biggest threat to Puaiohi, followed by avian malaria and habitat degradation and invasion of the forest by weeds.”
The study also looked at whether the introduced Japanese White-eye can fill the role the Puaiohi are filling, but found the White-eye eat smaller seeds are are spreading invasive plants.
In their study, authors urge the further support of efforts to conserve Puaiohi and to “consider introductions to other suitable areas to ensure the persistence not only of the species, but also its functional role in Hawaii’s montane ecosystems.”
“Non-native birds cannot adequately replace the seed dispersal services provided by Puaiohi,” Kaushik said.