Owls, often heard but rarely seen, are enigmatic creatures of the night. Their distinctive vocalizations are a complex communication system, offering glimpses into their hidden lives.
Beyond the Howl
Owls do not “howl” in the manner of wolves. Instead, they produce a diverse array of vocalizations, including hoots, screeches, hisses, whistles, barks, growls, whimpers, chirps, and chatters. These sounds are generated by a unique vocal organ called the syrinx, located at the base of the trachea. Sound production occurs as air flows through the syrinx, causing vibrations in its membranes.
Muscles connected to the syrinx modulate these vibrations, allowing owls to produce a wide range of pitches and qualities. Unlike mammals, which use a larynx for vocalization, birds rely solely on the syrinx, a structure that enables some species to produce multiple sounds simultaneously.
Why Owls Vocalize
Owls vocalize for specific purposes, centered on survival and reproduction. A common reason for their calls is territorial marking, where owls announce their presence to warn others away. Male owls often project rhythmic hoots to establish and defend their hunting grounds and nesting sites.
Vocalizations also play a significant role in mating and courtship rituals. Male owls use calls to attract potential mates, signaling their availability. Once paired, male and female owls often engage in duets, an exchange of calls that strengthens their pair bond and reinforces their shared territory. Calls also serve for general communication among mates and family members, facilitating contact and helping locate one another, such as parents guiding their owlets.
Owls also produce calls for warning and alarm, alerting others to danger or deterring predators and intruders. Harsh sounds like barks, growls, hisses, or bill snaps indicate a perceived threat. Young owlets frequently make distinct begging calls, often piercing screams, to solicit food from their parents.
A Symphony of Species
The vocalizations of owls vary significantly across different species, with each possessing a unique repertoire. For instance, the Great Horned Owl is well-known for its deep, resonant hoot, often transcribed as “hoo-h’HOO-hoo-hoo.” The male’s hoot is lower in pitch than the female’s due to his larger syrinx.
The Barred Owl produces a distinctive eight to nine-note call that sounds like “Who cooks for you? Who cooks for you-all?” Mated Barred Owl pairs often perform duets that include hoots, cackles, caws, and gurgles. In contrast, the Barn Owl does not hoot but emits a piercing, high-pitched shriek or screech. They also make other sounds like purring, clicking, and hissing. The tiny Northern Saw-Whet Owl is recognized by its repetitive “toot” or “beep,” which some describe as resembling a truck backing up.
When Silence Breaks
Owls are most often heard vocalizing during their peak activity times, which occur at dusk and dawn. The frequency and intensity of owl vocalizations also exhibit seasonal patterns.
Calling increases during breeding seasons, which fall in late winter and early spring for many species. Great Horned Owls, for example, vocalize from mid-September through early April, with their breeding season beginning in January and February. Environmental factors also influence when and how often owls vocalize; high winds and heavy precipitation can deter calling activity. Some species may call more frequently during brighter moon phases.