Data from: Community composition coupled with habitat fragmentation drives acoustic divergence in bird assemblages

Rapid expansion of human activities has altered abiotic and biotic
environments and reshaped the sensory systems of animal species. Auditory
perception, a key sensory component of soniferous species, is essential
for signal detection, species recognition, and group coordination. Birds
mitigate acoustic masking in fragmented habitats by actively modulating
the spectral and temporal features of their songs. However, it remains
challenging to determine whether these modulations are primarily driven by
biotic factors (e.g., species interactions within varying community
compositions) or by abiotic factors (e.g., island attributes). We surveyed
bird communities on forested islands in the Thousand Island Lake region,
China, using passive acoustic monitoring. We applied sound frequency-based
analyses to examine the relationship between island attributes (area and
isolation), acoustic assemblage composition (species richness,
morphological and phylogenetic relatedness), and sound frequency
modulation of birds on 12 islands. Our findings indicated that species
competition within acoustic space led to various strategies of frequency
modulation to avoid acoustic overlap. With increasing frequency overlap,
birds exhibited greater variations in peak frequency and frequency range,
reflecting decoupled modulation in which vocal adjustments occurred either
upward or downward, depending on context. By disentangling the effects of
community composition from island attributes, we found that acoustic
overlap was intensified on remote and small islands, particularly among
species with large body size or close phylogenetic relationships, driving
acoustic niche partitioning. These findings highlight the importance of
biotic interactions within animal communities in driving avian vocal
production shifts, emphasizing the necessity of jointly considering
community composition and gradients of abiotic factors when examining
sensory adjustments.