Data from: Loss of cultural song diversity and the convergence of songs in a declining Hawaiian forest bird community

The effects of population decline on culturally transmitted behaviors in animals has rarely been described, but may have major implications to population viability. Learned vocal signals in birds are of critical importance to behaviors associated with reproduction, intrasexual interactions, and group cohesion, and the complexity of vocal signals such as song can serve as an honest signal of an individual’s quality as well as the viability of a population. In this study, we examined how rapid population declines recently experienced by Hawaiian honeycreepers on the island of Kaua‘i (USA) may have influenced the diversity, complexity, and similarity of learned honeycreeper songs. We analyzed the acoustic characteristics of songs recorded during 3 time periods over a 40-year time frame for three species of declining Kaua‘i honeycreepers. We detected a loss of song complexity and diversity over the 40-year time period that paralleled dramatic population declines. Concurrent with the loss of complexity we also found that the acoustic characteristics of the three honeycreepers’ songs became more similar to another. To our knowledge, this is the first documentation of convergence of acoustic characteristics among rapidly declining species. The reduction of song complexity and diversity and convergence of songs not only signals a loss of culturally transmitted behaviors in these endemic Hawaiian honeycreepers, but also potential challenges to recovery of these rapidly declining species. Moreover, the present study highlights that there is a “hidden” cost to declining populations beyond just the loss of individuals that is not often considered, the loss of culturally transmitted social behaviors

Acoustic Characteristics of Three Kauai Honeycreepers

Data frame that contains 11 acoustic characteristics measured from songs of ‘akeke‘e (AKEK) (Loxops cauruleirostris), ‘anianiau (ANIA) (Hemignathus parvus), and Kaua‘i ‘amakihi (KAAH) (Chlorodrepanis stejnegeri). The characteristics include: 1) song length (total length of song from beginning to end, in seconds), 2) total number of syllables, 3) number of unique syllable types, 4) trill rate (total syllables/song length), 5) average number of notes per syllable, 6) average number of frequency changes (directional change, either ascending or descending) within a syllable, 7) number of frequency changes between syllables within the song, 8) peak frequency (dominant frequency, level at which the most energy is expelled within the song, in Hz), and 9) low (kHz) and 10) high (kHz) frequencies at which the amplitude exceeded -24dB relative to the peak frequency, and 11) frequency bandwidth (kHz) as the difference between high and low frequency. Songs were collected 1976-1978 (1970s), 2001-2004 (early 2000s), 2010-2017 (present day). Record ID corresponds to the identification number given to each sound file archived at The Macaulay Library at the Cornell Lab of Ornithology