Song repertoires of the Pied Flycatcher Ficedula hypoleuca of the Tomsk population: a comparative aspect of the advertising song in the urban and natural environment

Animals have just recently begun to inhabit cities which differ from natural ecosystems in a number of key ways. Wild birds' diverse behaviors, including communication, shift in urban settings. The structure of songs and its frequency-temporal features are vulnerable to change. However, little is known about how urban environments impact the song repertoires of birds. The purpose of this research was to compare and contrast the key elements of the pied flycatcher's song repertoire in urban and natural settings. The study was carried out between 2014 and 2022. The study focused on two Pied Flycatcher populations, "forest" and "urban," which reside in regions with different levels of anthropogenic impact. Data for the "forest" group were gathered 13 kilometers from Tomsk in the natural habitat of the species (56°20'56"N, 84°57'06"E). Two parks in Tomsk - "Camp Garden" (56°27'15"N, 84°57'00"E) and "University Grove" (56°28'08"N, 84°56'55''E) - were used to gather information on the "urban" group. The singing logs of 82 male pied flycatchers were examined ("forest": n = 34; "urban": n = 48). For each male, 75 song sequences were examined for each male. 6150 songs (60556 figures) in total were examined. The quantity of figures and the variety of figures were counted for each song. A unique number was given to each type of figure. The Pied Flycatcher's song is shorter and less diverse in urban settings (See Table 1). The reduced population density in the city can presumably be linked to the simplicity of songs in 'urban' birds. Males had repertoires with anywhere from 11 to 71 different types of figures. Both groups' repertoires had similar average sizes. In the population repertoire of birds, 173 different song figure types were found in the population repertoire of birds, with 156 types in the "forest" group and 147 types in the "urban" group. According to the Jaccard index (KJ = 0.75), the song repertoires of the birds in the analyzed groups showed a relatively high degree of similarity. The 13 figure types that make up the song base of the Pied Flycatcher population under study can be found in the repertoires of at least 50% of the males in each group. These 13 categories of figures represent the basic, conservative portion of the male repertoire. (See Fig. 2) We looked at the figures included in the repertoires of at least 50% of the males in any of the groups under study to evaluate the more variable part of the repertoires of the groups under study (See Fig. 3). The most common in both groups (for 70% of males or more) were figures that acted as connectors, starting elements, and as part of common motifs. A total of 17 figures were used similarly in the studied groups. For nine types of figures, a higher incidence (p < 0.05) of their inclusion was noted in the repertoire of males of the "forest" group and, for four, by those of the "urban" group was noted. This imbalance can be considered a consequence of the different rate of spread of certain "urban" figures in the repertoires of males and the loss of some "forest" figures. This is facilitated by the isolation of the 'urban' group due to its insular nature and high fidelity to former nesting places of the Pied Flycatcher. Similar patterns were revealed when analyzing the prevalence of different song constructions based on the figures considered in the male repertoires (See Fig. 4). Comparing how often a figure is used in a group song sequence, we found that only 4 figures were used equally by males in the studied groups (p > 0.05), which is 4 times less than when comparing repertoires (See Fig. 5). Eleven "forest" figures and fifteen "urban" figures are identified. The most frequent figures in the song sequence are those that are part of the bimotives, the basic structural components of the song of the Pied Flycatcher. In the forest, males more frequently incorporate figures forming the bimotif 21→22 into their songs, while in the city they incorporate 24→62 (p < 0.001). Figures of these motifs contribute the most to the song sequences of the groups under consideration, ranging from 6.8 to 9.1%. In addition to the figures of these bimotives in the forest, four types of figures (with a share of more than 1%) - No. 1, 102, 109, and 17 -are used more frequently. In the city, the number of such figures was five (No. 72, 73, 103, 5, and 94). Overall, it is conceivable to discuss the presence of 6-7 figures within a diversity of motives (with one bimotif predominating), which determine the key elements of pied flycatcher vocalization at the researched sites. Bimotives, the starting elements, and other figures with ambiguous functional roles all contribute to a lesser extent to establishing the distinctiveness of song sequence of the contrasted groups. Being a "technical" element of the song, the connectors have essentially no impact on the song specificity of the groups. The discrepancies that arise between the groups are likely influenced by the great level of nest site fidelity that male pied flycatchers have to past breeding locations. As "islands" or mosaic habitats, urban parks support the preservation of segregation between the study groups. Therefore, there is a requirement for maintaining the development of "song culture" in the city. The article contains 6 Figures, 1 Tables, 32 References. The Authors declare no conflict of interest.

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