Dataset from: Linking body condition and vocal signals: How the little auk, (Alle alle), chicks communicate their needs to parents

This repository contains acoustic datasets collected from little auk chicks (Alle alle) to investigate relationships between begging-call characteristics and chick body condition under natural and experimentally manipulated conditions. The study combines field data collected during two breeding seasons: a natural-condition study conducted in July–August 2017 and an experimental corticosterone-implantation study conducted in July–August 2012. The natural-condition dataset (Data_1 and Data _1a) includes recordings from 10 chicks (12 ± 1 days old) with similar hatching dates and body masses. Chicks were selected to ensure comparable age and synchronized recording sessions, minimizing potential environmental confounding factors such as weather variation or predator activity. This dataset includes acoustic parameters extracted from begging calls and a body-condition index calculated as residual body mass relative to the population mean for chicks of the same age (N = 32), following Quillfeldt (2002). Body-condition values ranged from –0.06 to 0.27. The experimental dataset (Data_2 and Data_2a) includes acoustic recordings from 10 chicks aged 10–12 days that received subcutaneous corticosterone implants (7.5 mg, 7-day release pellets) to simulate reduced body condition and food deprivation effects. Recordings were obtained twice for each chick: one day before implantation and two days after treatment. Corticosterone treatment resulted in a 5.5-fold increase in faecal corticosterone metabolite concentrations while remaining within the physiological range reported for the species. Three additional chicks received placebo implants as handling controls. All chick begging calls were recorded during the second week of life using in-nest microphones (Olympus ME 51S) connected to digital recorders (Olympus LS-3 and LS-P4). Recordings were stored in WAV format at 48 kHz sampling rate and 16-bit resolution. Analyses focused exclusively on high-quality rhythmic begging calls (“chirp”/“peep” calls), recorded during parental attendance and selected based on high signal-to-noise ratio, absence of wind artefacts, and lack of overlap with other vocalizations. The dataset contains acoustic measurements extracted from 874 begging calls recorded under natural conditions across 10 nests (30–152 calls per chick; mean ± SD = 87.4 ± 38.8), and 600 calls recorded in corticosterone-treated chicks (10 chicks × 30 calls before treatment and 30 calls after treatment). In natural conditions the mean number of begging sessions per chick was 8 (range 4–13), and the mean number of calls per session was 12 (range 8–16). In experimental conditions the mean number of begging sessions per chick was 4 (range 3–6), with a mean of 8 calls per session (range 5–10). Spectrogram analyses were conducted in Raven Pro 1.6.1 using a 512-sample Hamming window with 87.1% overlap (temporal resolution: 1.50 ms; frequency resolution: 86.1 Hz). Acoustic measurements were based on the fundamental frequency of individual syllables and included: syllable duration (duration), maximum fundamental frequency (freq_max), minimum fundamental frequency (freq_min), peak fundamental frequency (freq_peak), aggregate entropy (agg_entropy) and intersyllable interval duration . Aggregate entropy quantified overall signal disorder based on energy distribution across frequency bins, where higher values indicate greater acoustic complexity. Acoustic processing was performed in R (v. 4.1.3) using the Rraven and warbleR packages. Blinding procedures were applied during acoustic analyses to ensure that the analyst was unaware of chick body condition and treatment status during data processing. No randomization was performed because colony and chick selection depended on predefined biological and logistical criteria, including accessibility, age, and body mass, ensuring comparability among individuals. All data were collected as part of projects funded by grants from the National Science Centre, Poland, awarded to D.K. (grant nos. 2011/01/N/NZ8/04569 and 2017/26/D/NZ8/00005) and K.W.J. (grant no. 2017/25/B/NZ8/01417), and conducted at the University of Gdańsk.