The most prominent sources of information on the Snowy Owl comes mostly from the work done by scientists such as A. Watson, G. M. Sutton and D. F. Parmelee during the 1930’s thru the late 1950’s and then in the 1970’s by P.S. Taylor. Although they touched on the vocalization aspect of the life of the snowy owl, information beyond the observed is found to be very much lacking and there is still plenty of work yet to be done in order for us to gain a deeper understanding of this great bird.
As the snowy owl is mostly silent outside of the breeding season, there is some question to how reliant this particular owl is on vocalization (Birds of North America Online) and this is one of the areas in which more research is required. The sounds that are observable occur during the breeding season but even then there is not a definite distinction between song and call. The hoot is the closest vocalization that could be considered as song; however, this would require further research to dispel any doubts that a hoot does not belong to the category of calls. As of the research available thus far, the consensus is that hooting probably serves as song only sometimes. Hooting is rarely a vocalization that comes from females but is common among males and is often observed in territorial defense displays, very much similar to those of the Great Horned Owl. One example of this display was observed by Sutton during one of his studies: the head of the male was lifted, the throat swelled and the tail elevated so that it was sticking straight up into the air. For each of his four long, low hoots, the male bowed violently and booming hoots sounded in reply. The hoots themselves usually sound two at a time as hoo, hoo and can repeat to six or more in a row with one or two second intervals in between each set, the last set being the loudest. There is sometimes a ventriloquial quality to the sounds so it seems that the owl is vocalizing from the air or the ground when it is actually on its perch somewhere else and the sound can be heard from seven miles away (All About Birds). That being said, males can produce this particular sound from a variety of positions whether it is from the ground or a perch but most commonly during flight.
Along with the hoot, there are other defense type of vocalizations that are more clearly distinguished as calls. There is some variation in literature in how the different researchers have interpreted the calls so there are many different names or sound sequences that refer to the same type of call. Generally, both males and females emit a sort of loud, harsh, grating bark, the female’s being similar but higher in pitch, in the instance of nest disturbance or perceived threat (The Owl Pages). Another type of vocalization mentioned across the different studies is mewing primarily heard from females. These sound like a whining squeal or whistle usually heard in three types of situations: before and after a feeding, during a distraction display when the nest or territory is under a threat of some kind and during displacement coition. There is some differing information regarding the exclusivity of the call: Watson observed females mewing only while Sutton and Parmelee did observe a male produce a similar call that was lower in pitch and a repeated ka sound rather than the female’s ke (Birds of North America Online). The hiss is the call that both sexes produce when threatened and direct them at the intruding party; however, it is the male that is generally more vocal as it is he who has the bigger role in the defense of the nest and territory (Wiklund).
For the variety of calls the Snowy Owl has, there is no literature bearing evidence whether or not dialects of song exist since it is not firmly established if there even is a song. However, the fact that several researchers interpreted calls so differently from place to place during different times that research was going on, may be starting point for more research in that trajectory (Birds of North America). Along with that, as of yet, there is also no literature about the development of song but calls seem to be innate but there may be an element of learning as well. Chicks start to cheep soon after hatching which most likely is an innate behavior to communicate hunger or discomfort. After about two weeks, the chicks can hiss. Also, chicks exhibit non vocal communication through mandible snapping when handled by humans at 8-10 days old. Perhaps they are not physically able to produce the hissing sound or snap their beaks right after hatching and must develop physically in order to do so or they must learn those behaviors from their parents. Either way, there is a lot of research that is yet to be done in order to answer these questions.
All About Birds. 2014. Snowy Owl. Retrieved from The Cornell Lab of Ornithology online: http://www.allaboutbirds.org/guide/snowy_owl/sounds
Lewis, Deane. 2013. Snowy Owl (Bubo scandiacus). Retrieved from The Owl Pages: http://OwlPages.com
Parmelee, David F. 1992. Snowy Owl (Bubo scandiacus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/010/articles/sounds
Wiklund, C.G., and Stigh, J. 1938. Nest Defense and Evolution of Reversed Sexual Size Dimorphism in Snowy Owls Nyctea scandiaca. Ornis Scandinavica. pp. 58-62