A study conducted by University of Hawaii biologists has found that Hawaiian honeycreepers on the island of Kauaʻi are losing their songs.
The Biologists at UH-Hilo analyzed four decades of bird song recordings from Kauaʻi.
“We did this study specifically in Kauaʻi because it is in a real crisis mode,” said Kristina Paxton, post-doctoral researcher at UH Hilo and lead author of the study.
Honeycreepers are songbirds that use their songs to defend their resources and attract mates. They learn their songs through other birds of the same species.
The scientists studied three species of Hawaiian honeycreepers: ʻakekeʻe (Loxops cauruleirostris), ʻanianiau (Magumma parvus), and Kauaʻi ʻamakihi (Chlorodrepanis stejnegeri). These species have seen rapid decline of population in the wild likely from avian malaria and habitat loss, according to Paxton.
The study was prompted when David Kuhn, a guide on Kauaʻi and co-author on the paper noticed it was harder to distinguish between songs. “Kuhn was having a hard time telling one honeycreeper species from one another only by listening,” Paxton said.
Researchers were interested in finding out how a rapid decline in population can affect the structural components of the songs.
“If there are too few birds, and they are too spread out in the forest, then there are fewer birds to learn from, fewer song types to learn, and also an increased chance of losing song types,” Paxton said. “This can lead to songs with fewer notes, less variety of notes, and fewer songs learned in the environment.”
The study compared honeycreeper songs from the 1970s to the present day. A spectrograph was used to document changes in frequency and structure of the songs.
“When you go into the forest in Kauaʻi it is now quieter, and that’s losing a part of what makes the Hawaiian forest what it is. The quietness of the forest is a sign that the forest is facing challenges,” Paxton says.