Sholakili Song Diversity

Project: Individual- and population-level variation in songs of the White-bellied Sholakili (Sholicola albiventris)

The White-bellied sholakili is a highly vocal passerine found in the shady understory of the Shola Sky Islands of the Western Ghats. Renowned for its complex and variable song, this species exhibits remarkable diversity in vocalisations both within individuals and across populations.
Our research investigates patterns, functions, and drivers of this song diversity through a combination of acoustic analysis, genetic data, and ecological context.

1. Measuring Song Complexity

Our aim is to develop tools to quantify the variation and complexity in bird songs at the individual level.
We created a Note Variability Index (NVI) — a metric that uses spectrogram cross-correlation to measure note-level spectro-temporal variation within songs, producing a complexity score.
We validated the NVI across a global dataset of birds with varying song complexity.

Reference: Sawant et al., 2022 — Methods in Ecology and Evolution.

2. Rules of syntax and song sharing: long term monitoring of individual song variation

To understand how song complexity and note use change over an individual’s lifetime.
Ongoing field monitoring of marked individuals since 2019.
Assessing intra-individual song variability across years.
Investigating song sharing between neighbouring males over time.
Exploring whether song complexity reflects male quality or is an indicator of fitness.

3. Population-level song signatures & cultural dialects

To identify and compare cultural variation in songs across the species’ range.
Characterising population-level song signatures along a distribution gradient.
Comparing song dialects in isolated populations with genetic connectivity data obtained through Next Generation Sequencing.
Studying how landscape and environmental factors influence cultural transmission and genetic exchange.

4. Breeding phenology from Passive Acoustic Monitoring

To use automated acoustic monitoring to track breeding patterns using PAM.
Using singing frequency as a proxy for breeding activity.
Developing custom BirdNET classifiers for this species.
Investigating synchrony/asynchrony in breeding patterns

5. Female song and sex-based vocal differences

To examine female vocalisations and compare them to male songs.
Recorded colour-banded individuals that were molecularly sexed.
Compared song structure and note-sharing patterns between males and females.

6. Song sharing and kinship

To test whether related birds share more song elements.
Analyzing patterns of note sharing between socially and genetically related individuals.
Comparing related vs. unrelated individuals within one well-monitored population.

Publications:

Sawant, S., Arvind, C., Joshi, V., & Robin, V. V. (2022). Spectrogram cross‐correlation can be used to measure the complexity of bird vocalizations. Methods in Ecology and Evolution, 13(2), 459-472.
Sawant, S., Arvind, C., Joshi, V., & Robin, V. V. (2021). Song Richness Index: A measure to understand the diversity and repetition of notes in a birdsong. bioRxiv, 2021-12.

Study site: The Shola Sky Islands in the Western Ghats, >1400m ASL in the Anamalai - Palani plateau.

Fundings: Science and Engineering Research Board (SERB)