rocky habitats usually favored by the great horned and Eurasian eagle-owls, respectively. Vocalizations The snowy owl differ in their calls from other Bubo owls, with a much more barking quality to their version of a hooting song. Perhaps as many as 15 different calls by mature snowy owls have been documented. The main vocalization is a monotonous sequence that normally contains 2–6 (but occasionally more), rough notes similar to the rhythm of a barking dog: krooh krooh krooh krooh... The call may end with an emphatic aaoow, which is somewhat reminiscent of the deep alarm call of a great black-backed gull (Larus marinus). They will call mainly from a perch but also sometimes do so in flight. The krooh call of the male snowy owl may perform multiple functions such as competitive exclusion of other males and advertising to females. The calls of this species may carry exceptionally far in the thin air of Arctic, certainly over more than , and maybe even to as much away. The female has a similar call to male but can be higher-pitched and/or more guttural as well as single notes which are often disyllabic, khuso. Female snowy owls have also been known to utter chirps and high screaming notes, similar to those of the nestlings. Both sexes may at times give a series of clucking, squeals, grunts, hisses and cackles, perhaps such as in circumstances when they are excited. The alarm call is a loud, grating, hoarse keeea. Another raspier bark is recorded, sometimes called a "watchman's rattle" call, and may be transcribed as rick, rick, rick, ha, how, quack, quock or kre, kre, kre, kre, kre. A female attacking to protect her nest was recorded to let out a crowed ca-ca-oh call, whilst other owls attacking to protect the nest did a loud version of the typical call while circling before dropping down. They may also clap their beak in response to threats or annoyances. While called clapping, it is believed this sound may actually be a clicking of the tongue, not the beak. Though largely only vocal in the breeding season, leading to some erroneous older accounts describing the snowy owl as completely silent, some vocalizations have been recorded in winter in the northern United States. Initially, the young of the snowy owl have a high pitched and soft begging call which develops into a strong, wheezy scream at around 2