Low frequencies in the display vocalization of the Western Capercaillie (Tetrao urogallus)

Abstract

<jats:p>Only a few bird species are known to produce low-frequency vocalizations. We analyzed the display vocalizations of Western Capercaillie males kept in breeding centers and identified harmonically structured signals with a fundamental frequency of 28.7 ± 1.2 Hz (25.6–31.6 Hz). These low-frequency components temporally overlap with the Whetting phase (96% of its duration) and they significantly contribute to the distinct vocal expression between individuals. The resulting model of discrimination analysis classified 67.6% vocalizations (63%, cross-validated result) correctly to the specific individual in comparison to the probability by chance of 12.5%. We discuss a possible function of low-frequency components that remains unclear. The occurrence of such low frequencies is surprising as this grouse is substantially smaller than cassowaries (Southern cassowary <jats:italic>Casuarius casuarius</jats:italic> and Dwarf cassowary <jats:italic>Casuarius bennetti</jats:italic>) , the species that produces similarly low frequencies. Because these low frequency components temporarily overlap with the Whetting phase, they are hardly audible from a distance larger than several meters.</jats:p>

Revisiting the Chicken Auditory Brainstem Response: Frequency Specificity, Threshold Sensitivity, and Cross Species Comparison

“…We chose instead to keep stimulus duration between 1.25 and 6 ms such that all tone bursts included at least one wavelength. While there exist examples of infrasound in avian models, 39 - 43 the mechanisms for perception of sound below 100 Hz represent a current gap in research. Such findings would help support in vitro studies of ultra-low frequency neurons found in the chicken and barn owl auditory brainstem.…”

Sound amplitude (dB) of male Western Capercaillie Tetrao urogallus

“…During these periods, male Western Capercaillies form leks in particular forest areas (Wegge et al 2005) where male vocalizations are key components of their displays for both sexual selection and territorial purposes (Laiolo et al 2011, Coppes et al 2021. The characteristics of their calls have been shown to be associated with individual male or territory quality (Laiolo et al 2011, Hart et al 2020. Recent research has also shown the potential for using Western Capercaillie calls for population monitoring (Abrahams & Denny 2018, Abrahams 2019 and studies have demonstrated that male Western Capercaillie calls can be correctly identified by autonomous bioacoustics recorders.…”

“…These results may help design bio-acoustic sampling protocols by determining how many microphones are needed to adequately cover a given surface area to avoid population underestimates. These reference values are also important if we aim to obtain good-quality recordings of calls at individual level (Abrahams 2019, Hart et al 2020, which may be crucial for obtaining accurate population estimates and for the management of endangered species such as the Western Capercaillie.…”