Owls are known for their distinctive hoots, commonly transcribed as “hoo hoo” or “who who” sounds. These vocalizations serve several purposes for owls, including territorial defense, mating calls, and communication between parents and offspring. In this article, we’ll explore the reasons behind owls’ signature whooping calls and what the different calls signify.
Anatomy of the Owl Hoot
An owl’s hoot starts in its syrinx, which is the avian equivalent of the human larynx or voice box. The syrinx contains membranes that vibrate to produce sound when air passes through them. Owls have asymmetrical ear openings and facial discs of feathers that help direct sound waves towards their ears, allowing them to precisely locate prey and other owls by sound alone.
By contracting muscles to change the shape of their syrinx and adjust the airflow through it, owls can modulate their hoots in frequency, pitch, and amplitude. This gives each species a distinctive vocal signature used for identification. For example, a Great Horned Owl produces a low-pitched and drawn out “hoo-h’HOO-hoo-hoo-hoo” call that sounds like “Who’s awake? Me too.” A Barn Owl makes a harsh, raspy screech that carries far distances. The Eastern Screech Owl produces a haunting, quavering whinny.
Volume
One reason owls hoot loudly is simply to be heard over long distances in order to mark and defend their territories or attract mates. Their calls can reach up to 5 miles for the Great Horned Owl and over 3 miles for the Barred Owl. Owls will vigorously hoot to proclaim ownership of their hunting grounds and ward off intruders. They are most vocal during late fall and winter breeding seasons.
Frequency Range
Another key factor is the wide frequency range of owl hoots, which makes them stand out from background noise. The Great Horned Owl’s call ranges from just 100 Hz to over 3 kHz, allowing it to be easily picked up by conspecific owls across a wide area. High-frequency sounds don’t transmit through forests as far as low, rolling hoots. Calls are often repeated steadily, ensuring they don’t get lost among rustling leaves and other nature sounds.
Social Functions of Owl Hoots
In addition to territory defense, owl vocalizations serve a variety of social purposes:
Finding Mates
Male owls hoot to attract females during mating season. Single females will respond with hoots of their own to signal their location and receptiveness. Back-and-forth duetting helps the two owls find each other in the dark. Some species like the Great Horned Owl are monogamous, reuniting with the same mate annually.
Communicating with Mates
Once paired, an owl couple uses softer contact calls to maintain their bond and relay information. The male’s hoots reinforce his commitment to guarding and providing for his family. If the female leaves the nest, the male may hoot to guide her back. Hooting synchronizes the owls’ activities, such as trading off nest duties.
Begging Calls by Offspring
Baby owls beg for food from their parents with loud, raspy screams. Thesemimic the normal adult hoots to ensure they will be fed. The parents respond with soft hoots to indicate their approach. As the owlets mature, their begging calls drop in pitch and start resembling adult vocalizations.
| Owl Species | Example Call Audio |
|---|---|
| Great Horned Owl | |
| Barn Owl | |
| Eastern Screech Owl |
Evolutionary Advantages of Signature Hoots
Over millions of years, the stereotyped hoots unique to each owl species have evolved to maximize their effectiveness in the owl’s nocturnal environment.
Species Recognition
The consistent vocalizations allow owls to immediately identify owls of their own species. Responding only to their species’ call conserves energy and avoids unnecessary conflicts with other birds. Unique calls also help owls find appropriate mates.
Locating Calls in Space
The broad frequency range and repetitive pattern makes it easy to pinpoint the origin of hoots in three-dimensional space. This allows owls to respond to potential mates, rivals, or offspring effectively even on the darkest nights.
Adaptation to Habitat Acoustics
Different owl species’ calls have evolved for optimal transmission through their native habitats. Woodland owls like the Barred Owl have hoots that are adapated for forests. The Short-eared Owl’s high-pitched bark carries far across open grasslands. The Great Gray Owl produces deep booming notes that penetrate dense coniferous forests.
Significance of Variations in Hooting
Subtle variations in the timing, pitch, loudness, and pattern of hoots convey additional meaning and context beyond species recognition.
Territorial Warning
When an intruder provokes them, owls shift to louder, more frequent hoots to signal aggression. Abrupt hoots with less space between them act as an audible threat display to deter territorial infringement.
Alarm Calls
Owls make harsh, urgent alarm calls when predators like hawks approach the nest. These warn offspring of danger with a different tone from the hunger begging calls. The male often hoots from a distance to distract predators while the female defends the nest site.
Looking for Mates
Unmated owls give longer, more repetitive hoots during courtship season to attract partners over a wider area. Paired owls use a more subdued, intimate version of the call to maintain their bond. Soft melancholy cooing identifies a female who has lost her mate.
Identifying Individuals
By perceiving nuances in hoots, owls likely discern individual identities beyond species. Parents can distinguish their offspring’s begging calls from those of strange chicks. Studies indicate mate recognition based on hoots even in large populations.
Conclusion
The owl’s iconic hoot serves a complex array of purposes from claiming territories to bonding families. Next time you overhear the to-HOOing call of these birds of the night, listen closely. The particular tone, pitch, and tempo offers clues into the fascinating social world of owls. While the ominous hoots once raised superstitious fears, we now understand they are simply the owls’ ingenious adaptation for communication in darkness.
