Sonic Characteristics of the Landscape - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 34

Fig. 2.3 Relationship between breeding elevation and song length and total notes of extant
cardueline finches (Reproduced with permission from Snell-Rood and Badayaev 2008 )
A more variable and unpredictable environment seems to enhance learning and
innovation, elaborating signals of quality in this group of birds.
This result seems in contrast with the evidence collected by Briefer et al. ( 2010 ),
who have found a reduced sound repertoire among the species of finches living at
higher altitude. Apparently these two groups of organisms follow different
strategies under environmental constraints.
2.5 The Contribution of Vegetation Microstructure
and Macrostructure to the Sonic Environment
Vegetation is a complex system composed of soil, air, water, stems, trunks,
branches, and foliage of herbs, shrubs, and trees. Reverberation, absorption, and
scattering are some effects on acoustic signals caused by vegetation.
In forests, sound propagation is strictly connected with the ground effect,
scattering from tree trunks and branches, and absorption by leaves. Scattering, the
return of echoes from an object that intercepts a signal, is linked to the presence of