© Peaks Island Land Preserve

Female Snowy Owl
Photo © Diego Delso, delso.photo, License CC-BY-SA
8 December 2015
Cádiz, Spain
Wikipedia Commons Featured Photo

 

Snowy Owls


Snowy Owls at a Glance

Taxonomy

 

  • Order Strigiformes

  • Family Strigidae (Typical Owls)

  • Genus and species:

      Nyctea (Bubo ?) scandiaca

 

Identification

 

  • Large size (Males 55-64 cm, 700-2500 grams; Females 60-70 cm, 780-2950 grams)

  • Large white owl with inconspicuous ear tufts; brilliant golden-yellow eyes, black beak; eyelids are edged with black; female larger than male

  • Male plumage – almost entirely white except for sparse grey or brown barring on back, wings or tail

  • Female plumage is moderately to extensively barred above and below; wings and tail are more barred; crown shows black spotting

  • Juveniles are darker overall with feathers spectacled

 

Behavior/Habitat

 

  • Voice – when disturbed a repeated“kre” call; male may utter a low, rapid, repeated cackling “ka”; female may utter a more high pitched “ke”; male can make a loud, booming, “hoo, hoo” in double and up to six times; male’s ‘song’ – “goo-goo” (female a higher pitch); alarm call is “kre-kre-kre”

  • Major food items – lemmings and other voles

  • Other food items – carrion, birds, mammals, fish, amphibians, crustaceans, and beetles

  • Feed mostly dusk and dawn; feed all hours in summer with continuous light; in winter feed in continuous dark

  • Small prey eaten headfirst while larger prey are torn apart before eating

           

Breeding/Nesting

 

  • Breed from May to September

  • Monogamous – often pair for life with occasional polygyny and polyandry

  • Nest is a scrape on ground; elevated on a hummock or rock for good view of surroundings; depending on food supply a clutch of three to eleven eggs

  • Incubation is 31-33 days

  • Male supplies food

  • Female broods and feeds chicks

  • Chicks: greyish white down

  • Parents care for chicks up to 10 weeks

 

Migration:

  • Migrate in unpredictable manner depending on conditions. Some may stay near breeding grounds, some migrate south, some are nomadic in Arctic tundra.

  • Juvenile males migrate furthest south; adult females migrate furthest north

 

References

 

del Hoyo, J., Elliott, A., and Sargatal, J. eds. (1999). Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds. Lynx Edicions, Barcelona (pages: 194-195)

Full Species Account

For more information on the movements and behavior of these mysterious Snowy Owls, please visit https://www.projectsnowstorm.org/

 

 

Snowy Owls with large heads, bright yellow eyes, almost white plumages, and five-foot wingspans are ferocious predators of the North. This owl is one of the largest owls (up to 6 pounds) in the world and in North America, it is probably – the largest owl. New DNA sequence data suggest a close relationship to the horned owls perhaps placing the Snowy Owl (genus Nyctea) into their genus – Bubo. (1)

 

Plumages vary in male and female, and juveniles. Young owls’ white plumages are decorated with more black spots and bars than the nearly all white adult. The intensity of black spots and bars between male and female varies: the male is usually overall whiter. The toes and tarsals are covered with feathers, characteristic of other species found in colder environments. (2)

 

Snowy Owls communicate using short calls. If disturbed they utter  a “kre” call followed by a more serious alarm call – a “kre-kre-kre” that sounds like a bark. Males make a low, rapid, repeated cackling “ka”; a female delivers a more high pitched “ke”.  The male can form a loud, booming, “hoo, hoo” that is repeated up to six times. The male’s  ‘song’ is a  “goo-goo”. The female has a higher pitch to her ‘song’. (3) Threats may induce a type of clapping – the sound originating either from the beak or tongue (1).

 

The Snowy Owl breeds in the circumpolar Arctic tundra. They move about before the breeding season  - finding the best food source for their upcoming young. This owl does not generally adhere to nest site fidelity, as is practiced by most other bird species. The Snowy Owl will follow cyclic movements of the lemming (related to voles), their favorite food. Population explosion of lemmings occurs in 4-year cycles resulting in food scarcity for this rodent. The lemmings migrate to a more suitable locale with available food. The owls follow where the lemmings go. (4) If lemmings become scarce, then they favor young ptarmigans for food (1).

 

The Snowy Owl nest is a scrape in the ground, elevated off the ground on hummocks or rocks. This elevation provides better surveillance of the conditions around the nest. A typical clutch size can range from three to eleven eggs. In Canada where conditions were ideal one year, 32 fledglings hatched out of 33 eggs. Higher abundance of food sources allows for the female to lay more eggs – she is more fat and fertile. The male supplies the female with food items while she broods and feeds the chicks. (1, 4)

 

These owls are nomadic and will travel great distance during the non-breeding season in search of food.  If the owl goes north into endless darkness and ice, its food source includes sea ducks found at ice-breaks - polynyas (5) and perhaps fish (3), but little is known about these intrepid owls. Snowy Owls that migrate south of their breeding range will eat carrion (4), birds, mammals, amphibians, crustaceans, and beetles (3, 4). Small prey is eaten headfirst while larger food items are torn about – even de-feathered. Birds as large as the Great Blue Herons, Canada Geese, and Brants are not out of reach from these fierce predators – nor are skunks, hares, and feral cats (1, 4a).

 

Snowy Owls are serious predators and this behavior invites other bird species to react by attacks. Long-tailed Skuas that already have a reputation as annoying mobbers (dive bomb and strike) are relentless in harassing these owls on their breeding grounds (2).  Other threats include attacks on their nests and competition for lemmings by Arctic foxes, corvids, dogs, grey wolves, and other avian predators such as large owls and eagles. Brutal conflicts with large owls and eagles may result in the Snowy Owl losing – sometimes fatally. (1)

 

References:

1. Wikipedia: Snowy Owl

2. Holt. D.W. et al. (1999). Family Strigidae. Pp. 91 and 106 in: del Hoyo, J., Elliott, A., and Sargatal, J. eds. (1999). Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds. Lynx Edicions, Barcelona.

3. del Hoyo, J., Elliott, A., and Sargatal, J. eds. (1999). Handbook of the Birds of the World. Volume 5. Barn-owls to Hummingbirds. Lynx Edicions, Barcelona (Pp: 194-195).

4. Weidensaul, Scott. 2014. Have Lemmings, Will Travel.

 (4a) Cited Norman Smith from Blue Hills Trailside Museum, Milton, MA and SNOWstorm collaborator)

5. Kaufman, Kenn. 2013. Audubon: Questions and Answers about Snowy Owls.

 

By Patty Wainright

Reviewed by Michelle Brown, Michael LaCombe, Marty