The study, led by Cristian Pérez-Granados and an international team of ornithologists, set out to do something rarely attempted: compare how songs and calls, the two main categories of bird vocalizations, respond to individual, population, and geographic factors within the same species. Songs are typically complex, learned, and tied to sexual selection, while calls tend to be shorter, more innate, and used for immediate communication such as territorial defense. Because these signals follow different developmental pathways, the team reasoned they might respond differently to habitat fragmentation, population size, and social isolation, providing complementary windows into population health.

Dupont’s lark proved an ideal model. Males sing and give territorial calls at high rates during the hour before dawn, and the species’ communication system is already known to be shaped by landscape structure. Songs are learned after juveniles disperse from their natal areas, by copying nearby adult males, and typically consist of three to eight discrete types. Territorial calls, by contrast, are learned before dispersal during a short learning phase in summer, likely from parents and neighbors in the natal patch, and consist of just one to three short whistles repeated regularly. This difference in timing means that songs and calls should carry information about movement and social interaction at different life stages.

Between March and June of 2024 and 2025, the researchers surveyed 27 habitat patches spanning the two main strongholds of the species in Spain, the Ebro Valley and the Iberian System. Patch areas ranged from 14 to 1,903 hectares and local male abundance from three to 77 individuals. Working in the pre-dawn darkness, they recorded 188 singing males with directional microphones and high-resolution digital recorders, capturing at least two minutes of song per male, sufficient to document the complete individual repertoire. For calls, they recorded a minimum of three calls per individual, ultimately sampling 74 calling males across 11 populations. When no birds were detected during repeated visits, autonomous recorders were deployed to confirm genuine absence.

The acoustic analysis was meticulous. A single expert scanned all recordings through spectrogram inspection in Raven Pro, delineating each vocalization and classifying it into types based on morphology, temporal patterns, frequency characteristics, and note structure. When classifications were uncertain or types appeared across populations, additional experienced ornithologists reviewed the material, and types were only confirmed when at least two researchers agreed. The final catalog contained 396 distinct song types drawn from 4,208 annotated songs, and 60 call types from 634 annotated calls. These were converted into presence-absence matrices allowing the team to compute repertoire sizes at both individual and population levels, and to quantify acoustic similarity between every pair of males using the Jaccard index.

The results revealed a striking divergence between the two vocalization types. Individual song repertoire size did not depend on population size, but varied significantly between regions, with Ebro Valley males singing larger repertoires than those in the Iberian System. At the population level, however, song repertoire size increased significantly with the number of territories, likely because larger patches host multiple local dialects among neighboring groups of males. Call repertoires, whether measured per individual or per population, showed no relationship with population size, geography, or sampling effort. Songs, in short, behave as flexible cultural traits molded by social environment, while calls remain remarkably conservative and spatially stable.

The spatial analysis sharpened this contrast. Acoustic similarity between males declined steeply with distance for both signal types, but calls were always more similar than songs at every scale examined. Neighboring males within 500 meters shared substantial portions of both repertoires, with mean song similarity of 0.48 and call similarity of 0.60, both far above random expectations. Between populations, similarity collapsed to almost nothing. Fine-scale analysis in 100-meter distance classes uncovered a telling threshold: song similarity declined steadily and leveled off beyond roughly 500 meters, while call similarity remained relatively constant up to a kilometer. Because adults disperse only about 100 to 150 meters, the wider coherence of calls hints that juveniles move at least a kilometer within their natal patches before dispersing, offering a rare behavioral clue about a life stage that has remained almost entirely invisible to researchers.

The most consequential result came from a two-decade natural experiment. The team revisited 50 populations originally monitored between 2004 and 2007, spanning most of the European range, and asked whether historical mean song repertoire size predicted population fate in 2025. A binomial logistic regression delivered a clear answer: populations with larger individual song repertoires had significantly higher persistence probabilities. Extinct populations had averaged 4.9 song types per male, compared with 5.7 in those that survived. Only one extinct population, five percent, had exceeded a mean repertoire size of 6.0, whereas 43 percent of surviving populations did, and not one of the nine populations with means above 6.25 was lost over the following twenty years. This threshold, the authors suggest, may mark the point below which extinction risk rises markedly.

The researchers are careful to note that population persistence depends on many interacting pressures, from wind farm development and grazing regimes to genetic erosion, habitat quality, and extreme weather events. Yet the strength of the acoustic signal is hard to ignore, and it validates, on a far broader geographic scale and a much longer timescale, an idea first proposed in 2008: that a cultural trait can serve as a predictor of population viability. Because vocal repertoire size can be measured non-invasively from field recordings, even with autonomous units, it offers managers a practical, low-cost indicator for tracking population health before declines become irreversible.

Beyond its conservation implications, the study fills a fundamental gap in behavioral ecology. Most research on avian vocal behavior has focused on songs and alarm calls, rarely comparing multiple signal types within the same species. By showing that songs and calls follow partially independent ecological rules, shaped by different learning schedules, dispersal stages, and social contexts, the work demonstrates how much information is layered into a dawn chorus. For a species clinging to fragmented fragments of Spanish steppe, those layers may now determine whether conservationists hear its song for decades to come, or only its echo.

Subject of Research: Acoustic communication, vocal repertoire size, and population viability of the endangered Dupont's lark

Article Title: Singing and Calling Behavior of a Threatened Passerine With Spatially Variable Vocalizations: Individual, Population and Geographic Patterns

Article References: Pérez‐Granados, C., Alonso‐Moya, C. D., Barrero, A., Sáez‐Gómez, P., Bota, G., Lahoz‐Monfort, J. J., Laiolo, P., Méndez, M., Serrano, D., Tella, J. L., Vögeli, M., & Traba, J. (2026). Singing and Calling Behavior of a Threatened Passerine With Spatially Variable Vocalizations: Individual, Population and Geographic Patterns. Ecology and Evolution, 16(9), Article e74380. https://doi.org/10.1002/ece3.74380

Image Credits: AI Generated

DOI: 10.1002/ece3.74380

Keywords: Dupont's lark, birdsong, vocal repertoire, bioacoustics, habitat fragmentation, population viability, conservation, cultural transmission, acoustic similarity, dialects, steppe birds, early-warning signal