Soundscape and Landscape Ecology - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 9

Fig. 1.2 Biophonies have different patterns during the year according to latitude. ( a ) At intertrop-
ical latitudes, animals are acoustically active all year around. ( b ) In temperate regions, biophonies
have a major peak in spring and a second peak in early autumn. ( c ) At the highest latitudes, there is
a peak only in the middle of summer, with a dramatic reduction of biophonic sounds during the rest
of the year
This phenomenon activates communicative channels that concur to the acoustic
complexity that we can hear around us. The apparent complexity of the acoustic
communication largely depends on factors such as species-specific acoustic perfor-
mance, population density, number of species composing the local aggregation
(community), time of the day, and season, and finally by the typology of the
vegetational cover (biomes and ecoregions). All these factors are strongly affected
by geographic positioning along the parallels.
With the use of digital technology, the expansion of magnetic memory and
highly sophisticated microphones and amplifiers assembled into programmable
devices for long-time autonomous (in terms of power supply) operation, the
recording of soundscapes has made a leap forward during the last decennia. Despite
these tremendous improvements, however, until now there have not been processes
able to identify automatically every type of sound. This limitation poses problems
in the identification of the components of a soundscape and largely reduces the
possibility of efficient evaluation of the potentialities expressed in distinct sites.
At the moment it is not possible to identify all the species that compose a
soundscape, but nevertheless new approaches are available.
Acoustic diversity, expressed in terms of frequencies, became an important
matter of investigation and of estimation of the complexity that we can expect in
a specific site or habitat. Acoustic diversity cannot be correlated with biological
diversity, at least in birds (Gasc et al. 2013 ), but nevertheless a high acoustic
diversity is associated with a specific assemblage of species. In fact, species such
as birds that have a special organ, the syrinx, to produce sounds, are able to produce
a great variety of sounds.
Biophonies present different dynamics according to the temporal scale of
resolution.
Observations of a breeding colony of European starlings at the University Farm,
Wytham (Oxfordshire, UK) by Wright and Cotton ( 1994 ) have demonstrated the
alternation of singing momentum with feeding activity at the ground. This alterna-
tion occurred twice per hour, but as egg-laying time approached, the majority of
birds spent their time close to the breeding colony.