Locatable and Nonlocatable Acoustic Signals for Barn Owls

Abstract

It is generally accepted that complex songs, ornamental color patterns, and elaborate courtship displays of animals are communicatory signals. However, factors that govern their design features, such as acoustic and optic characteristics, have received little attention (Konishi 1970; Morton 1970). Marler (1955) made the first attempt to discover adaptive significance in the physical structure of animal sounds. He reasoned that there are signals adapted for easy location of their sources and sounds suitable for confusing location by predators. The physical differences between these two types of signals reflect the differences in their function. Marler used human psychophysical evidence to explain why certain acoustical properties make signals more or less suitable for location. Direct nonhuman experimental evidence for his theory is lacking.