Monitoring temporal change of bird communities with dissimilarity acoustic indices

Abstract

Summary A part of biodiversity assessment and monitoring consists in the estimation and track of the changes in species composition and abundance of animal communities. Such a task requires an important sampling over a broad‐scale time that is difficult to reach with classical survey methods. Acoustics may offer an alternative to usual techniques by recording the sound produced by vocal animals. Animal species that use sound for communication (sing and/or call) establish an acoustic community when they sing at the same time and at a particular place. The estimation of the acoustic community dynamics could provide indirect cues on what drives changes in community composition and species abundance. Here, new methods were developed to estimate the changes in bird communities recorded at three woodland temperate sites in France. Both field recordings and simulated data were used to test whether acoustic dissimilarity indices can be used to estimate changes in the composition of the community. Four dissimilarity indices found in the literature, and a new one named Dcf were tested on auditory spectra after transformation to the Mel scale, rather than on classical Fourier frequency spectra. All indices were compared with each other and with compositional indices. The results show that bird communities occurring at the three sites were dynamic with changes of composition with time. Dissimilarities computed on simulated acoustic communities were correlated with compositional dissimilarity but those computed on field‐recorded communities could not be considered as faithful estimators of community composition variations. However, the indices indicate important dates in community changes around mid‐April that were also seen in the composition dynamics. Acoustic dissimilarity indices failed to track accurately changes in species composition of the bird communities. However, these indices, which are easy to compute, still provide information on the acoustic dynamics of bird community. Acoustics might not be considered as a proxy of compositional diversity but rather as another facet of animal diversity that needs to be studied and preserved on its own.