The Swainson’s hawk (Buteo swainsoni) is a medium-sized raptor found in western North America. Like other hawks, the Swainson’s makes a variety of vocalizations, from loud, screaming alarm calls to softer contact calls used to communicate with others of its kind. The most common sounds made by Swainson’s hawks include a high-pitched, whistling “klee-yer” call, as well as a rapid “kik-kik-kik” call during flight displays. Understanding the sounds of Swainson’s hawks can help birders identify and appreciate these graceful predators.
Alarm Calls
When faced with danger or a potential threat, Swainson’s hawks produce a loud, screaming call described as “klee-yer.” This piercing call typically lasts for a few seconds and is often repeated multiple times in alarm situations. It serves to alert other hawks in the area to potential danger. Swainson’s employ their alarm call when defending nests from predators, warning off competing hawks from territories, and signaling to young hawks to take cover. The alarm call carries well over long distances, allowing Swainson’s hawks to communicate alarm across their wide-ranging habitats in the western United States and Canada. This high-pitched scream is one of the most recognizable sounds of the Swainson’s hawk.
Contact Calls
Swainson’s hawks use softer contact calls to locate mates and offspring, establish pair bonds, and defend territories. These contact calls are lower-pitched and more drawn out compared to the piercing alarm scream. Contact calls can sound like a whistling “klee-yer” or “kloo-yer.” They may incorporate chirps or clicks as well. Pairs of Swainson’s hawks engage in calling duets to strengthen their bond. These softer vocalizations allow hawks to communicate without eliciting alarm. Swainson’s refine their contact calls annually, so the subtle variations help hawks identify individuals and family members across seasons. Contact calls are especially important after breeding season when Swainson’s gather in large migratory flocks for their long journey south.
Flight Calls
A third common vocalization of the Swainson’s hawk is a rapid “kik-kik-kik” heard during flight displays. In the spring and summer breeding season, Swainson’s perform dramatic flight displays to defend territories and attract mates. These circular aerial shows incorporate clapping of wings and dives alongside vocalizations. The quick “kik” sounds are thought to be made by specialized wing feathers. The combination of soaring flight maneuvers and “kik” vocalizations advertise the fitness of a hawk during the breeding season. Swainson’s hawks may also produce this flight call in other social situations like group roosting. Distinguishing this aerial call helps identify the aerial displays of Swainson’s hawks across western North America.
Habitat and Range
Understanding the habitat and range of Swainson’s hawks provides helpful context for listening to their vocalizations. Swainson’s hawks breed in open country across much of western North America. They inhabit prairies, plains, deserts and agricultural areas from Alaska to Mexico. Though found predominantly in the western U.S. and Canada during summer, Swainson’s are long-distance migratory birds. They journey remarkable distances each fall to wintering grounds in southern South America. The wide variety of habitats occupied throughout the year expose Swainson’s hawks to diverse predators and risks. Their vocal signals allow them to communicate threats across varied landscapes.
Breeding Grounds
During spring and summer, Swainson’s hawks become widespread across open habitats of western North America. They breed from Alaska south to northern Mexico, and east into Minnesota, Iowa and Missouri. Within their large breeding range, Swainson’s occur at relatively low densities. But certain areas – like pockets of central California or southeast Idaho – host thriving populations. On their breeding grounds, Swainson’s nest solitarily or in loose colonies, constructing stick nests high in trees or on utility structures. Here the hawks employ loud alarm calls and flight displays to defend nests sites. Listening for these territorial signals can alert researchers to check for active Swainson’s hawk nests in an area.
Migration
One of the most epic migrations in the animal kingdom belongs to the Swainson’s hawk. In fall, after the breeding season, Swainson’s hawks gather in massive flocks numbering in the thousands of individuals. Together, they migrate from western North America to southern South America – a journey of over 5,000 miles one-way for some hawks. This migration takes the birds over Mexico, Central America, and down through Brazil to central Argentina and surrounding regions. During migration, Swainson’s rely on contact calls and flight displays to communicate and coordinate movement as a flock. Their vocalizations are less frequent but remain important during this nomadic phase.
Wintering Grounds
On their wintering grounds in South America, Swainson’s hawks occupy open habitats in Argentina, Uruguay, southern Brazil and Paraguay. Here they roost communally, sometimes joining flocks of over a hundred thousand hawks. Even on the wintering grounds, Swainson’s maintain their vocal skills. They use contact calls and alarm screams as needed to identify roost-mates, claim food resources and avoid danger. Maintaining vocalizations year-round enables returning migrants to re-establish pair bonds and territories the following spring.
Conservation Status
Though still relatively common, Swainson’s hawk populations declined in the 20th century from habitat loss and exposure to pesticides. These threats diminish on migration and wintering areas that were less studied. Recent research into Swainson’s migration patterns and winter ecology has helped conservationists better protect the species across its full annual range. Surveying Swainson’s hawk vocalizations remains an important census method during the breeding season. Tracking migratory flocks also provides key data. With greater knowledge and habitat protections in place, Swainson’s hawk numbers have rebounded from their low point in the 1980s. Continued conservation and appreciation of Swainson’s hawks will hopefully ensure thriving populations – and continued opportunities to hear their iconic voices – across western North America.
Conclusion
Swainson’s hawks produce a variety of vocalizations that allow them to effectively communicate across the diverse habitats they occupy. By learning the sounds of these graceful raptors, bird enthusiasts can better detect and identify them in the field. Key vocalizations to listen for include the loud, whistling alarm scream “klee-yer”, the softer contact calls like “kloo-yer” that help maintain pair bonds, and the “kik-kik-kik” flight calls incorporated into aerial displays. Understanding the habitat range and migration patterns of Swainson’s hawks provides helpful context, as their sounds vary in meaning between the breeding season, wintering grounds, and migration. With responsible conservation efforts, the voices of Swainson’s hawks will continue resounding across the skies of the western United States and Canada. Taking time to appreciate the sounds of these raptors connects us to the natural cycles and wildlife that shape the cherished landscapes of North America.
