Measurements
Both Sexes
- Length
- 8.3–11 in
21–28 cm - Wingspan
- 21.7–24.4 in
55–62 cm - Weight
- 3.3–7.6 oz
93–215 g
Other Names
- Tengmalm's Owl, Richardson's Owl
- Nyctale boréale (French)
- Lechuza de Tengmalm (Spanish)
Cool Facts
- The female Boreal Owl is much larger than the male. The species shows the most extreme reversed sexual dimorphism of any American owl.
- The Boreal Owl finds its prey by sound. It can locate mice even through vegetation and under snow.
- The ear openings on a Boreal Owl's skull are asymmetrical, with one opening high up on the skull and the other much lower. The different positions of the holes help the owl find exactly where a sound comes from, helping gauge height as well as distance.
- Boreal Owls usually are considered monogamous, with one male mating with one female. Several studies in Europe found that one male may mate with up to three females, and a female occasionally mates with two different males. They found that such multiple mating occurs most frequently when mice numbers are at their highest. (Finding easy prey to feed the young means that less help is needed in raising young owls.) When mice numbers were low, all the owls were monogamous.
Habitat
Forest
Lives in boreal forests with spruce, aspen, poplar, birch, and balsam fir. In mountains of West, found in subalpine forests of fir and spruce.
Food
Mammals
Small mammals, birds, and insects.
Nesting
Nesting Facts
- Clutch Size
- 1–19 eggs
- Egg Description
- White.
- Condition at Hatching
- Helpless, eyes closed, covered in white down.
Nest Description
Nests in tree cavity, usually old woodpecker hole. Adds no nesting material. Also uses nest boxes.
Nest Placement
Cavity
Behavior
Aerial Dive
Hunts at night from perches.
Conservation
Least Concern
Widespread and common in boreal forest, but reliable population estimates not available. Considered a "sensitive" species in range in United States outside of Alaska. Relies on mature and dead trees for nesting sites, and so is sensitive to clear cutting.
Credits
- Hayward, G. D. and P. H. Hayward. 1993. Boreal Owl (Aegolius funereus). In The Birds of North America, No. 63 (A. Poole, and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C.