Owls are nocturnal predators often revealed by their unique and sometimes startling acoustic output. They use a wide range of sounds for complex communication, reaching significant volumes that define the nighttime soundscape. The study of owl acoustics focuses on the loudness achieved by large species and the specialized anatomy that produces their calls.
The Spectrum of Owl Vocalizations
The sounds owls make depend heavily on the species, extending well beyond the familiar hoot. The Great Horned Owl, for example, produces a deep, rhythmic series of hoots, often transcribed as “hoo-hoo-hooooo,” used for long-distance communication. In contrast, the Barn Owl is known for harsh, high-pitched screeches and screams. Smaller species, like the Eastern Screech-Owl, use different sounds, including a descending whinny and a soft, monotonic trill for close-range conversation. Owls also utilize mechanical sounds, such as a sharp bill snap paired with a hiss, which is a defensive action used to deter threats.
Quantifying the Noise
Powerful owl calls can reach high volumes, allowing messages to travel long distances at night. The hoot of a large species like the Great Horned Owl has been measured at 70 to 90 decibels (dB) at the source. This volume is comparable to a running garbage disposal or a loud vacuum cleaner, and significantly louder than typical human conversation (around 60 dB). Although sound decreases over distance, the low frequency of large owl hoots allows the sound wave to travel further through dense forest with less attenuation. Juvenile owls begging for food often produce high-pitched screeches that register in the 75 to 95 dB range, demanding attention from their parents.
The Mechanism of Sound Production
Owl sounds originate not from a larynx, as in mammals, but from the syrinx, a specialized avian vocal organ. This structure is located deep in the chest, at the base of the trachea where it branches into the two main bronchi. Air passing through the syrinx causes internal membranes and soft tissue masses (labia) to vibrate, generating sound without vocal cords. The syrinx’s low position provides an acoustical advantage, contributing to the deep, resonant quality of the classic owl hoot and projecting sound effectively over distance. In some species, the syrinx musculature allows each side to vibrate independently, theoretically permitting the owl to produce two distinct tones simultaneously.
The Purpose of Vocalizations
Owl vocalizations are functional tools used for various behavioral needs during their nocturnal lives. The loudest and most frequent calls establish and defend territory from rivals, especially during the non-breeding season. Male owls use characteristic hoots as territorial advertisement, signaling their presence to other males and potential mates. During the breeding season, calls attract partners, sometimes involving elaborate duets between a male and female pair; the female’s call is often higher pitched due to her smaller syrinx size. Communication also occurs between family members, with parents using softer calls to maintain contact, while young owls use persistent, high-volume screeching to beg for food.