Study Shows Best Management Options to Boost Native Bird Survival

A recent study found only 494 Puaiohi are left in the wild, and all of them are on Kaua‘i. Photo courtesy of DLNR

A new study from Kaua‘i’s Alakaʻi Wilderness Preserve has demonstrated how different types of management may enable the long-term survival of the Puaiohi, a critically endangered native thrush that is central to maintaining healthy native forests, according to a news release from the state Department of Land and Natural Resources.

With fewer than 500 puaiohi left in the wild, maintaining this small population of the last remaining native seed dispersing species is of particular importance.

Researchers at the University of Hawaiʻi at Mānoa and the Kauaʻi Forest Bird Recovery Project (KFBRP) looked at how different types of management options would influence the population size of the puaiohi and found that rat control, even at more conservative levels, appeared to be the most effective method of increasing puaiohi abundance. Female and juvenile survival appeared to be the most important influences on population growth and persistence, so management should focus on increasing female and juvenile puaiohi survival. Both are very susceptible to rat predation.

The study was led by Dr. Jean Fantle-Lepczyk at UH Mānoa, in collaboration with KFBRP and researchers at UH Mānoa. Fantle-Lepczyk was happy to find that, in addition to rat removal, other management options, such as providing nest boxes and supplemental food and improving native habitat, have potential to increase puaiohi numbers.

Puaiohi, or Small Kaua‘i Thrush. Photo by Lucas Behnke.

The puaiohi is also one of the last six endemic forest bird species to remain in Kaua‘i’s Alaka‘i Wilderness. Kauaʻi has lost five of its native birds in recent decades and those that survive are restricted to a small area of high elevation forest. They are at risk from introduced predators, such as rats and feral cats, avian malaria, and habitat degradation due to feral livestock and invasive plants, in addition to natural threats such as drought and hurricanes.

Fantle-Lepcyk said, “This study shows that practical, attainable management activities can increase Puaiohi numbers and prevent the extinction of this unique endemic species. Because many of the issues facing puaiohi are the same as those faced by the other Hawaiian forest birds, the recommended management activities could have a substantial and valuable positive impact on the other remaining endemic birds of the Alaka‘i.”

KFBRP Project Coordinator, Dr. Lisa Crampton, said, “This study is important because it helps justify the enormous time and effort KFBRP, its partners and the public (via the very successful “Birds, Not Rats!” campaign) is investing in rat control in the Alaka‘i.