Are communication activities shaped by environmental constraints in reverberating and absorbing forest habitats?

Abstract

In the dense vegetation of temperate or tropical forests, communication processes are constrained by propagation-induced modifications of the transmitted sounds. The presence of leaves, trunks and branches induces important sound reverberation and absorption leading to diminution of the signal energy as well as qualitative modifications. The aim of this paper is to briefly review the different strategies used by birds to manage with these constraints. At the emitter's level, an adapted emission behavior which takes into account both the physical heterogeneities of the forest environment and the temporal variations of the acoustic constraints, is especially useful to control the active space of signaling. The coding of information into acoustic parameters that have different susceptibility to propagation constraints is also of great interest. At the receiver's level, an adaptive reception behavior (listening post) and a great tolerance to sound degradation during the decoding process are the keys to an optimal communication process.

Are high perches in the blackcapSylvia atricapillasong or listening posts? A sound transmission study

“…Furthermore, selective frequency filtering, reverberation and atmospheric turbulences distort amplitude and frequency patterns over time, giving recorded sounds a blurred appearance ͑Wiley and Richards, 1982;Dabelsteen et al, 1993͒. Songbirds seem to have evolved different strategies to counteract degradation. For instance, sounds used for longrange communication may be fitted to the properties of the transmission channel by their frequencies ͑Morton, 1975; Dabelsteen et al, 1993;Nemeth et al, 2001;Mathevon et al, 2004͒. It is also believed that active choice of sender and receiver positions may indicate an adjustment to the heterogeneous forest environment made of various superposed layers of vegetation with different conditions for sound propagation.…”

Song Perch Height in Rufous‐and‐White Wrens: Does Behaviour Enhance Effective Communication in a Tropical Forest?

“…Like all forms of animal communication, acoustic signals are distorted from their original structure as they transmit through the natural environment from one individual to another (Wiley & Richards 1982; Bradbury & Vehrencamp 1998; Slabbekoorn 2004). Animals have evolved multiple strategies to ensure that their messages are heard by intended receivers (Arak & Eiriksson 1992; Mathevon et al. 2004).…”

“…Like all forms of animal communication, acoustic signals are distorted from their original structure as they transmit through the natural environment from one individual to another (Wiley & Richards 1982;Bradbury & Vehrencamp 1998;Slabbekoorn 2004). Animals have evolved multiple strategies to ensure that their messages are heard by intended receivers (Arak & Eiriksson 1992;Mathevon et al 2004). For example, the acoustic adaptation hypothesis proposes that animals' vocalizations change over time to become structured in a way that reduces attenuation (decrease in signal strength) and degradation (distortion of temporal and amplitude patterns) in their particular environment (Rothstein & Fleischer 1987;Brown & Handford 2000;reviewed in Boncoraglio & Saino 2007;Barker 2008).…”