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Snowy Owl

Bubo scandiacus

Order:
Strigiformes
Family:
Strigidae
Sections

Sounds and Vocal Behavior

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Figure 4. Attitude of male during Territorial Hooting in May and early June.

Hooting males can be heard more than 2 miles away. By J. Zickefoose, after Taylor 1973.

Vocalizations

Development

No information on developmental process. However, chicks within the egg give gentle piping vocalizations. Female not known to respond to a vocalizing chick or assist in hatching. Not known if vocalizations within shell are heard by other shell-bound siblings, perhaps speeds up the hatching process, as reported in waterfowl and other birds.

Vocal Array

Newly hatched young give a vocalization similar to that heard from pipping eggs, but stronger and twittering. Thought to be food-begging call, but could have several functions. By about 2 wk old chicks give strong wheezy scream (DWH) or hissing (Watson 1957), believed to be a food begging call. Prior to leaving the nest at about 3 wk of age, a loud scream, shrill, or squeal develops. This call is continually given by nest-departed young on the tundra, and appears to function as food begging call. May also help adults locate chicks (Parmelee 1972, DWH). Food begging calls continue at least until fledging and perhaps beyond, until the parent-offspring bond breaks (Parmelee 1992). Food-begging type calls are also heard on winter grounds in communal roosting situations, but their function remains unknown (DWH). Not known when adult-like vocalizations are first give; likely by winter and certainly by the next breeding season.

As with most owl species, Snowy Owls have a diverse vocal repertoire, often sex-specific, although both sexes seem capable of all vocalizations. For example, Snowy Owls hoot, bark, grunt, scream, whistle, and twitter, among other vocalizations.

All songs and calls can have multiple functions not fully understood by researchers (Parmelee 1992). For example, hooting appears to serve several functions such as, territorial singing with competing males, advertising to females, and nest defense (Watson 1957, Taylor 1973, Parmelee 1992).

Hoots are given primarily by breeding males, described as a single hoo or double hoo, hoo, but sometimes several given rapidly (Watson 1957, DWH). Also a long drawn-out hooooo, less often heard (DWH). Hooting was reportedly heard up to 11 km by Sutton (see letter, in Bent 1938, p. 359); > 3 km distance by Taylor (1973), and from 3-10 km (Voous 1988). These distances seem unlikely.

A detailed phonetic description has been provided by Watson (1957). However, these descriptions are often difficult to interpret, due to variation in the way people report them. Thus, many descriptions by different authors are actually the same vocalization. All the phonetics need not be described.

Females frequently give a call described as a whistling mewing call (Watson 1957), which occurs before and after feeding by the male, during distraction displays, and in displacement coition. Watson heard this call from females only, and Sutton and Parmelee (1956) heard it from only one of many males they observed. A crowed ca-ca-oh is given by attacking females at the nest, but not recorded for males (Sutton and Parmelee 1956). Males give a low, rapid, cackling ka-ka-ka-ka-ka-ka in displacement coition or when alighting on a favorite perch (Watson 1957). A similar, though often higher pitched, ke-ke-ke-ke-ke is given by females before displacement coition, at the start of pre-coition display, and when feeding young.

One of best descriptions for courtship behavior and vocalizations was reported by Taylor (1973). He reported Snowy Owl territorial hooting as similar to that of the Great Horned Owl. Courtship hooting declined by mid-June, as nesting behaviors ensued. However, hooting is loud, intense and also frequently given during nest defense (Taylor 1973). Threat hooting can be given from the ground (Taylor 1973) or from the air while circling an intruder (DWH). When hooting from ground male Snowy Owls lean forward, lower head, raise tail, and hoot (Taylor 1973, DWH; Figure 9). This is similar to Sutton's (1932, Watson's (1957), and DWH's description. Females show the same posture when hooting, but they hoot infrequently (DWH). See Behavior: predation (nest defense).

Other than hooting, Snowy Owls have a diverse vocal repertoire when defending chicks at or near the nest - as do most owls species. For example, one of the most often heard vocalization is the “bark” (DWH) which has variously been described as the so-called “watchman's rattle” by Thaxter (1875) and is probably the rick, rick, rick heard by Wheelwright (in Witherby et al. 1952), the ha, how, quack, quock, or quawk, reported by Sutton and Parmelee (1956), and the kre, kre, kre, kre, kre reported by Watson (1957). The call is given commonly during flight and from a perch. It appears to function as a threat, and is given by both sexes when humans approach nests. Not known if the same vocalization given when foxes, bears, or other predators approach nests. See also Cramp (1985) for detailed descriptions of vocalizations.

Phenology

Wintering Snowy Owls were formerly thought to be silent, but this might reflect a lack of reporting (Weir 1973, Evans 1980). Voice is now reported to aid in winter territoriality as residents often scream at intruders, termed “territorial screaming display” (Evans 1980), accompanied by posturing. This vocalization and display were also given with no apparent territorial context. Evans (1980) also reported 10-15 soft grating sounds similar to those reported by Sutton (1932) on the breeding grounds. Other vocalizations included a soft warbling, and a grunt, each heard twice (Evans 1980). Flying owls tended to elicit stronger responses from conspecifics than perched owls. Except for the grunt, DWH has heard similar sounds by wintering Snowy Owls. Grunts have also been heard by nesting females (DWH). It is not surprising Snowy Owls vocalize in winter, but further study is needed to link voice and behaviors.

Daily Patterns

Not well known, but likely most vocal during the onset of pair formation and breeding. Nest defense and territorial defense can occur at any time of day due to any number of circumstances. Probably much less vocal during winter, but daily circumstances also likely elicit various responses not associated with breeding.

Sexual Differences

Females have higher-pitched voice than males. Studies in Barrow, AK, report differences in nest defense duties between sexes for vocal and physical behaviors (DWH). Females often scream from nests, apparently a food begging call, but similar calls are directed at researchers during distraction displays when protecting nests (DWH). Males hoot more and scream less than females. Both sexes bark.

Places Of Vocalizing

Most vocalizing has been described from breeding grounds and associated with pair formation, brood care, nest defense, and defense of flightless chicks departed from nests. Known to vocalize from the ground, or flight, depending on circumstances.

Nonvocal Sounds

As in all owl species, both adult Snowy Owl sexes snap / pop their bill loudly when threatened. Nestlings capable of bill-snapping when about 8 to 10 d old, when being handled (Watson 1957, DWH).

Recommended Citation

Holt, Denver W., Matt D. Larson, Norman Smith, Dave L. Evans and David F. Parmalee. 2015. Snowy Owl (Bubo scandiacus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA. https://doi.org/10.2173/bna.10