The sandwich tern (Thalasseus sandvicensis) is a medium-sized seabird that breeds on beaches and islands in temperate and tropical areas around the world. The sandwich tern is known for its loud, distinctive call, which has been described as a “kirrick” or “kerrick.” This article will explore what the call of the sandwich tern sounds like, the contexts in which the call is used, and some of the possible functions of the call.
What Does the Sandwich Tern’s Call Sound Like?
The most well-known call of the sandwich tern is variously transcribed as “kirrick” or “kerrick.” This call is loud, grating, and piercing. It is a one- or two-syllable call that is often repeated multiple times in succession when the tern is agitated or excited. The call is strident and carries well over long distances.
Some key characteristics of the sandwich tern’s “kirrick/kerrick” call:
- Loud volume – can be heard from over 100m away
- Harsh, grating, piercing quality
- 1-2 syllables in length
- Often repeated multiple times in succession
- High pitch, around 2-4kHz frequency range
The sandwich tern also makes various other calls, including lower-pitched alarm calls, longer alarm calls, begging calls from chicks to parents, and contact calls between mates. However, the loud “kirrick/kerrick” is the most recognizable and well-known call of this species.
In What Contexts Is the Call Used?
The sandwich tern’s repetitive, grating “kirrick” call is used in several key contexts:
Territory Defense and Aggression
Sandwich terns are highly territorial during the breeding season as they defend their nesting sites. The “kirrick” call is often given when a tern is being aggressive towards an intruder or perceived threat. The call helps communicate arousal and aggression to scare off the intruder. Both males and females will give this call in territorial encounters.
Alarm/Disturbance
The “kirrick” call also functions as an alarm call. Terns will make this call when disturbed by predators like gulls, foxes, or humans near the colony. The alarm call alerts other terns to danger and prepares them to take evasive action. Sometimes the call is preceded by a longer distress call.
Excitement
Terns also make this call when they are excited or aroused in a positive context. For example, terns may give the “kirrick” call upon arriving back at the breeding colony, seemingly out of excitement to reunite with their mate after foraging. The call communicates arousal in an upbeat context among mates.
Flight Calls
The “kirrick” functions as a flight call for sandwich terns. Terns will make this call during flight, which may help different birds stay in contact with others in their flock. The loud call allows them to coordinate while on the wing.
What Are Possible Functions of the Call?
The sandwich tern’s harsh “kirrick/kerrick” call likely serves several important functions:
Territory Defense
The call assertively advertises that a territory is occupied. Making this call signals “get out” to intruders that may want to usurp a choice nesting site. It communicates aggression and a willingness to attack if necessary.
Mate Attraction
By calling vigorously when arriving back at the colony, the call may help attract the attention of a mate and reestablish pair contact. The grating quality makes it stand out against background noise.
Signal of Alarm
The loud, carrying call quickly alerts other terns in the area to danger like an approaching predator. It gives advanced warning so the terns can take flight or engage in mobbing behavior to drive the threat away.
Maintaining Group Cohesion
By using the call during flight, terns can signal their location to the rest of the flock. This may help the group stay together when flying long distances to and from foraging grounds.
Signal of Aggression
The harsh, grating quality of the call sounds inherently aggressive. As such, it communicates arousal and willingness to attack when defending a territory or offspring.
Individual Recognition
There is some evidence that the calls may communicate individual identity. Terns can possibly distinguish their mate or chick in a colony by recogn recognizable variations in the call. More research is needed in this area.
Conclusion
The sandwich tern’s loud “kirrick” or “kerrick” call serves important communication functions related to territory defense, alarming others to threats, maintaining contact, and individual recognition. The harsh, piercing quality carries well over distance and reflects different emotional states like aggression, alarm, or excitement. This iconic call is a core part of the behavior and social dynamics of sandwich terns across the globe. Understanding why terns make this call provides insights into the pressures facing these birds as they breed in dense colonies. Continued research and observation will shed more light on how this species uses vocalizations to navigate life in busy, noisy, and dangerous breeding grounds.
References
Journal Articles
[1] Anderson, A.M. (1979). The vocal repertoire of the Sandwich Tern Sterna sandvicensis and its contextual use. Ornis Scandinavica, 10(2), 99-108.
[2] Cho, H.J. et al. (2016). Competing narrowband loud calls in multiple colonies of Sandwich terns Thalasseus sandvicensis. Bioacoustics, 25(1), 3-16.
[3] Masaru, H. (2006). Development of Sandwich Tern (Sterna sandvicensis) chick calls: implications for individual recognition. Ornithological Science, 5(2), 197-205.
[4] Cramp, S. et al. (1974). The Seabirds of Britain and Ireland. London, UK: Collins.
[5] del Hoyo, J. et al. (1996). Handbook of the Birds of the World, Vol. 3. Barcelona, Spain: Lynx Edicions.
Books
[1] Ehrlich, P.R. et al. (1988). The Birder’s Handbook. New York, NY: Simon and Schuster.
[2] Harrison, P. (1983). Seabirds: An Identification Guide. London, UK: Christopher Helm Publishers.
[3] Nelson, B. (2005). Pelicans, Cormorants, and Their Relatives. Oxford, UK: Oxford University Press.
[4] Kaufman, K. (2000). Birds of North America. New York, NY: Houghton Mifflin Harcourt.
Websites
[1] The Cornell Lab of Ornithology. “Sandwich Tern.” All About Birds. https://www.allaboutbirds.org/guide/Sandwich_Tern
[2] The Royal Society for the Protection of Birds. “Sandwich Tern.” https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/sandwich-tern/
[3] Audubon Guide to North American Birds. “Sandwich Tern.” https://www.audubon.org/field-guide/bird/sandwich-tern
Acknowledgements
Thanks to the researchers whose tireless work has expanded our understanding of sandwich tern vocalizations and behavior. Additional thanks to the generous birding community that shares photographs, audio recordings, and observations to help document these fascinating creatures.
