Biology subjects

Burchardt, L. S.

Publications and source records attributed to Burchardt, L. S..

5 recordsLinked to original sources

bioRxiv2026

Seabird calls are shaped by prosody, efficiency, and rhythmic encoding

In the search for universals shaping acoustic communication across species, we increasingly look for patterns known from human languages and music in non-human animals. These parallels are often explored separately and with limited ecological context. Here, we take a deep dive into the temporal structure of a complex call used by the little auk (Alle alle), a pelagic seabird with elaborate vocal behaviour and socially complex colonial life. Based on syllable durations, intervals and silences, we examine its conformance to linguistic laws, rhythmic structure and information content. This reveals intricate problems of temporal organisation: while the calls conform not only to linguistic laws of brevity but also to the initial and final lengthening known from human prosody, these effects interact with the internal structure of the call and information carried within it. To our knowledge, this is the first time that conformance to multiple linguistic laws, exceeding simple vocal efficiency, has been described for a non-human, non-vocal learning animal. The calls rhythmic structure shows a progressive rallentando -- a systematic slowing driven by changes in syllable and silence durations and the intervals between syllable onsets. The exact patterns of this rallentando are indicative of the callers sex and individually specific. These results reveal how seabird communication is shaped not only by efficiency universals, but also the specific pressures of colonial life. Our work highlights the temporal structure as an important axis of communication evolution, but also serves as a reminder to consider the species ecological reality and the function, not only presence, of temporal organisation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/713940v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@1e35c7eorg.highwire.dtl.DTLVardef@1cd74f6org.highwire.dtl.DTLVardef@1b9f7b7org.highwire.dtl.DTLVardef@364180_HPS_FORMAT_FIGEXP M_FIG C_FIG

animal behavior and cognition↗

bioRxiv2025

Unique rhythmic signatures in arrhythmic birdsong

Animal rhythms are gaining increasing attention in the studies of behaviour and musicology. Recently, it has been shown that rhythm itself can be used as an information coding channel. Now we ask: does this hold true for arrhythmic sequences? To answer that, we analysed songs of the tawny pipits (Anthus campestris), migratory songbirds known for their simple songs. Using focal recordings of 384 individuals from six populations collected across their European breeding range, we calculated an extensive set of rhythmic and temporal indices to describe each song. First, the pattern of these songs was inspected and shown to be arrhythmic. Second, songs belonging to specific individuals and populations were compared using permuted discriminant function analysis and supervised uniform manifold approximation and projection. To describe the level of individuality of the rhythmic structure alone, we calculated Beechers statistic for all songs, as well as the potential of identity coding for each parameter separately. We show that tawny pipit males sing using individual rhythmic patterns in their arrhythmic songs, and that modern rhythmic indices, such as beat precision and integer ratios, are among some of the most individually distinct parameters of their songs. Furthermore, contrary to previous investigations based on the spectral shape and basic frequency and temporal characteristics of these songs, we show that the species displays population-specific temporal patterns, with significant differences throughout its European range. This study is the first to demonstrate geographic scale differences in birdsong rhythm, and to show that rhythmic analysis can provide useful descriptions of arrhythmic sequences.

animal behavior and cognition↗

bioRxiv2025

Yellowhammer (Emberiza citrinella) males sing using individual isochronous rhythms and maximise rhythmic dissimilarity with neighbours

The temporal structure of an animals vocal output can be cognitively controlled, presenting an interesting aspect for vocal learning species that benefit from diversification. Although birdsong is the most thoroughly studied aspect of animal communication, its rhythms remain largely unknown. Here, we revisit the question of vocal individuality in the songs of male yellowhammers (Emberiza citrinella) purely from a rhythmic perspective. Yellowhammers use simple songs composed of two phrases: the initial phrase, with one individual usually having a repertoire of on average two such phrase types, and the dialect phrase containing the dialect that is the same for all males at a given locality. Some of the initial phrases are commonly shared between various males, but their combinations and frequency contours are individually unique and temporally stable. Using focal recordings of 38 known individuals, collected over three years in the same geographic location, we calculated a set of nine temporal indices to describe each song and compared individuals in a permuted discriminant function analysis. Subsequently, we calculated the potential for individual coding for each of these parameters. To assess whether rhythmic similarity may depend on the singers proximity, we calculated vocal dissimilarity as the Euclidean distances between each two males, and used Kendalls correlation. We show that yellowhammer males use individual rhythms, maintained over different phrase types and carried mostly in the inter-onset-interval variability and syllable rate, as in syllables per second, within the song. There were particularly strong rhythmic differences between singers among the closest neighbours, which decreased over the first 600 m. There was no pattern for neighbours beyond this distance. This study is the first to demonstrate the existence of strong individuality based purely on rhythm, as well as rhythmic differentiation from neighbours, in a songbird. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=52 SRC="FIGDIR/small/660106v1_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@1727ccorg.highwire.dtl.DTLVardef@35cb5borg.highwire.dtl.DTLVardef@1b9db10org.highwire.dtl.DTLVardef@dd1f4d_HPS_FORMAT_FIGEXP M_FIG C_FIG

animal behavior and cognition↗

bioRxiv2023

The human voice aligns with whole-body kinetics

Humans often vocalize while concurrently gesturing with their hands. Fluctuations in the intensity and tone of the voice have been shown to synchronize with gestural upper limb movement. This research provides direct evidence that interactions between arm movements and postural muscle activity cause these voicing fluctuations. We show that specific muscles (e.g., pectoralis major, erector spinae), associated with upper limb movement and their postural anticipations, are especially likely to interact with the voice. Adding mass to the upper limb increased this interaction. Ground-reaction forces were also found to relate to postural muscles, and these measurements also directly covaried with fluctuations in the voice during some movement conditions. These results show that the voice co-patterns with whole-body kinetics, i.e. forces. We thereby go beyond kinematic analyses in studying interactions between gesturing and vocalization, invoking several implications for biomechanical modeling. We conclude that human voicing has evolved in a dynamical interaction with the whole-body motor system.

neuroscience↗

bioRxiv2023

Postural and muscular effects of upper-limb movements on voicing

Voice production can be a whole-body affair: Upper limb movements physically impact the voice in steady-state vocalization, speaking, and singing. This is supposedly due to biomechanical impulses on the chest-wall, affecting subglottal pressure. Unveiling such biomechanics is important, as humans gesture with their hands in a synchronized way with speaking. Here we assess biomechanical interactions between arm movements and the voice, by measurement of key (respiratory-related) muscles with electromyography (EMG) during different types of upper limb movement while measuring the bodys center of mass. We show that gesture-related muscle activations scale with positive peaks in the voices amplitude. Some of these muscles also strongly associate with changes in the center mass, confirming that gesture-vocal coupling partly arises due to posture-related muscle activity. If replicated, these results suggest an evolutionary ancient gesture-vocal connection at the level of biomechanics. These preliminary results will support a pre-registration of analyses for a larger-scale confirmatory study.

neuroscience↗