A recently published study from the heart of Kauaʻi’s Alakaʻi Wilderness Preserve has revealed that Puaiohi, a critically endangered native thrush, plays a key role in keeping the rainforest healthy. This delicately patterned songbird eats native fruits and disperses their seeds, but it is estimated that there are fewer than 500 birds left in the wild. Researchers with the Kauai Forest Bird Recovery Project (KFBRP) looked at whether the introduced Japanese White-eye can fill this niche but found that White-eyes prefer smaller seeds and are also spreading invasive plants.
KFBRP Project Coordinator, Dr. Lisa Crampton, said, “Kauaʻi has experienced extinction and catastrophic declines in fruit-eating native bird species, combined with the introduction of non-native species. Our results underscore how important it is to protect Puaiohi if we want preserve Kauaʻi’s montane ecosystem. This is the only native songbird capable of dispersing larger seeds in the rainforest”.
The study was led by Dr. Monica Kaushik, a Fulbright Fellow at Colorado State University (CSU), in collaboration with KFBRP and Dr. Liba Pejchar of CSU. Kaushik was surprised to find that sites with Puaiohi received substantially higher ‘seed rain’ (number of seeds caught in seed traps) even though fruit abundance was the same. She says, “Non-native birds cannot adequately replace the seed dispersal services provided by Puaiohi. If Puaiohi continue to be rare and their range is restricted, we’re likely to see important changes in the plant community, such as increased numbers of invasive or small-seeded plants. Other native plants might fail to regenerate altogether”.
Kauaʻi 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.
This latest study adds to the body of evidence showing that the loss of native birds jeopardizes the fate of native plants. This has consequences for people as the forest provides humans with free ecosystem services such as flood water attenuation, filtration, and fertilization for fields downstream.
Co-author Dr. Liba Pejchar agrees: “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”.