Slope orientation strongly shapes how far bird song travels and which direction singers face

Evidence

Generally acoustic communication is observed and studied in flat areas or on gentle slopes, and when moving along the steep sides of a mountain range the topographic constraint immediately appears that modifies direction and intensity of the sonic ambient. In fact, the sonic ambient is strongly influenced by the steepness and by a nonuniform distribution of the acoustics waves that are not easily perceived. So, steepness not only affects abundance, distribution, and movement of organisms but also the communication of vocal animals. Birds that sing upslope have a greater far distribution of sonic energy, and in contrast birds singing downslope have a very narrow distribution of sound (Fig. 4.12) Hunter (1989) reports an interesting observation made on 40 birds, including 21 passerine birds, during their singing behavior along a steep slope in the Kulu and Ravi valleys of the Western Himalayas, India. Of 48 observations 37 were upslope, 9 parallel to the slope, and only 2 downslope, confirming the strong orientation of birds on steep slopes. — Almo Farina, Soundscape Ecology, 753

Categorization

• XREF: connects to: Sounds originate from landscape structure and need three perspectives to describe — Almo Farina, Soundscape Ecology: Principles,…, 245; Landscape slope and creek rocks act like a volume knob and notes — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 995

Broader Connections

• Landscape slope and creek rocks act like a volume knob and notes #corroborates (0.85) — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 995
• Sounds originate from landscape structure and need three perspectives to describe #expands (0.80) — Almo Farina, Soundscape Ecology, 245