Western screech-owls (Megascops kennicottii) are a species of small owl found throughout western North America. They produce a variety of vocalizations used for communicating with other owls and defending their territories. Screech-owls are famous for their eerie, shivering calls, which have led to their association with spooky stories and myths. However, these mysterious birds actually utilize a complex repertoire of sounds to go about their daily lives. In this article, we’ll explore the different calls Western screech-owls make and what they mean.
Screeches
The most iconic vocalization of the Western screech-owl is a series of tremulous, wailing hoots commonly transcribed as “oo-oo-oo-oooh.” These screeches serve several purposes for the owls:
- Defending territories – Screeches warn other owls to stay away.
- Attracting mates – Screeches help male and female owls find each other during breeding season.
- Begging calls – Hunger screeches by baby owls tell their parents they need food.
The screeches start quietly, rising in a crescendo before fading away. They can last up to 6 seconds. Interestingly, the pitch of screeches is lower in larger owls and higher in smaller owls. Screeches are most often heard during nighttime hours when the owls are active. However, agitated owls may screech at perceived threats during the day as well.
Variations in Screeches
The screech is not just one uniform call. Ornithologists have described different variations that likely serve different purposes:
- Territorial scream – A shorter, more aggressive screech.
- Whine call – A high-pitched squeal indicating distress or agitation.
- Begging whine – A longer whine made by baby owls when hungry.
By listening closely, observers can start to distinguish between the different screeches and infer the owl’s intentions.
Trills
In addition to the signature screeches, Western screech-owls also produce a rapid series of short notes known as a trill. These trills serve two main functions:
- Contact calls – Trills help the owls keep track of their mate or families at night when hunting and roosting.
- Alarm calls – Trills warn of incoming danger or intruders.
The trills consist of around 10 individual notes per second, sounding like a bouncing ball to our ears. They carry well through vegetation and enable the owls to communicate over distances. Trills may shift to screeches if an approaching predator fails to heed the first warning.
Differences Between Male and Female Trills
Interestingly, male and female Western screech-owls make slightly different trill sounds:
- Male trills are lower pitched and slower.
- Female trills are higher pitched and faster.
This dimorphism allows the owls to identify each other’s gender when calling out over long distances. The ability to pinpoint a potential mate’s location is very useful during the breeding season.
Other Vocalizations
Western screech-owls have an extensive vocal repertoire beyond just screeches and trills. Here are some other sounds they make:
Snore Call
A snoring sound made by the male when delivering food to the female at the nest. It signals his approach so she doesn’t mistake him for a predator.
Barking Call
A low croaking or barking sound used in aggressive encounters with other screech-owls. It indicates a readiness to attack if challenged.
Moan
A mourning moan made by both sexes after pairing up or before nesting. May help strengthen the pair bond.
Bill Snapping
The owls often snap their bills together to warn of impending attack. This sound can frighten away predators or competitors.
Clucks
A rapid clucking or chuckling denotes anxiety or excitement in the owl. It is made in agitated circumstances.
Whistle
A descending whistle is sometimes given by the male when delivering food. May signal the female that he has returned to the nest.
When are the Vocalizations Heard?
Western screech-owls are primarily nocturnal, so most of their vocalizations are heard from dusk to dawn. However, they may call at any time of day or night when agitated. The various calls serve different functions in the owl’s daily life:
- Evening – Trills and contact calls locate mates and family.
- Night – Screeches defend territories and deter predators.
- Pre-dawn – Trills and screeches call mates and offspring back to the roost.
- Nesting season – Screeches and moans establish pair bonds, mark nest sites.
- Anytime – Alarm calls sound in reaction to threats.
Understanding when each type of vocalization is likely to occur provides clues into the owl’s behavior and intentions.
Why Do They Vocalize at Night?
Most owl vocalizations occur at night because that’s when the birds are active and need to communicate over distances. There are several reasons why nighttime calls work better:
- Cooler air allows sound to travel farther.
- Less ambient noise from other birds and animals.
- Darkness makes visual signals ineffective.
- Territory defenses are strongest at night when intruders are expected.
The calls allow mated owls to remain in contact while flying and hunting at night. And loud screeches quickly warn off any encroaching rivals.
Interpreting Screech-Owl Vocalizations
Here are some tips for listening to Western screech-owl calls and determining their meaning:
- Shivering hoots = territorial defense
- Faster, higher trills = female calling
- Slower, lower trills = male calling
- Loud, repetitive screeches = alarming a threat
- Softer, wavering screeches = communicating with family
Practice identifying the different screeches, trills, and other vocalizations. With experience, you’ll be able to decipher the language of these mysterious night birds.
Mimicking Western Screech-Owl Calls
It is possible to mimic the calls of Western screech-owls to draw them in for observation. Here are some tips:
- Use a whistle, recorder, or your own vocal cords.
- Master their trill pattern and pacing.
- Begin calls 30 minutes after sunset when owls become active.
- Try a territorial scream first to elicit a response.
- Follow with contact trills to keep them interested.
- Imitate begging calls to bring in adults with food for young.
Always imitate calls sparingly and respectfully. Excessive mimicry may distress the owls. And be patient – the owls may take 15-30 minutes to respond.
Unique Adaptations for Nocturnal Vocalizations
Western screech-owls possess specialized adaptations that aid their vocal abilities at night:
- Asymmetrical ear placement – Owls can triangulate sound sources more accurately.
- Facial disc – Funnels sound waves towards the ears.
- Soft edges on primary feathers – Allows for silent flight while hunting.
- Large vocal repertoire – More vocal complexity for communication in darkness.
These adaptations allow Western screech-owls to live and communicate effectively under cover of darkness when most other birds and animals sleep. Their nocturnal lifestyles shaped the evolution of their unique voices.
Significance of Vocalizations
For small, nocturnal raptors like Western screech-owls, vocal communication is essential for:
- Claiming nesting and hunting territories.
- Locating mates over distances.
- Coordinating parental care duties.
- Staying in contact with family members at night.
- Warning off competitors and predators.
Without the ability to vocalize complex messages, screech-owls would struggle to survive, mate, raise young, and defend resources. Their wide array of calls, from trills to shrieks, are key adaptations that enable their success as tiny raptors of the night.
Conclusion
The calls of Western screech-owls have an air of mystery around them, but in fact serve many important purposes in the owl’s life cycle. From defending territories to caring for young, the screeches, trills, barks, moans, and other vocalizations form a complex language that allows screech-owls to communicate and function in the darkness. By listening closely and observing context, we can better understand these vocal messengers of the night. Screech-owls show amazing adaptation in using sound so effectively as their primary sense under cover of darkness. The wide variation in their vocalizations reflects the diverse array of information they need to convey to survive and reproduce. So next time you hear the wavering hoots of a screech-owl piercing the night, listen closely to decipher its meaning!
References
Smithsonian’s National Zoo & Conservation Biology Institute. “Screech Owl Sounds.” https://nationalzoo.si.edu/animals/screech-owl
The Cornell Lab of Ornithology. “Western Screech-Owl Life History.” https://www.allaboutbirds.org/guide/Western_Screech-Owl/lifehistory
Sibley, D. (2016). The Sibley Field Guide to Birds of Western North America. New York: Knopf.
