- 8.3–11 in
- 21.7–24.4 in
- 3.3–7.6 oz
- Tengmalm's Owl, Richardson's Owl
- Nyctale boréale (French)
- Lechuza de Tengmalm (Spanish)
- 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.
- The oldest recorded Boreal Owl was a male, and at least 8 years old when it was recaptured and rereleased during banding operations in Idaho.
Lives in boreal forests with spruce, aspen, poplar, birch, and balsam fir. In mountains of West, found in subalpine forests of fir and spruce.
Small mammals, birds, and insects.
- Clutch Size
- 1–19 eggs
- Egg Description
- Condition at Hatching
- Helpless, eyes closed, covered in white down.
Nests in tree cavity, usually old woodpecker hole. Adds no nesting material. Also uses nest boxes.
Hunts at night from perches.
Boreal Owls are widespread and common in boreal forest, but reliable population estimates not available. They are considered a "sensitive" species in the United States outside of Alaska. Partners in Flight estimates a global breeding population of 1.7 million, with 24% living in Canada, and 6% living in the U.S., They rate a 10 out of 20 on the Continental Concern Score, and are not on the 2014 State of the Birds Watch List. Boreal Owls rely on mature and dead trees for nesting sites, and the species is sensitive to clear cutting.
- 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.
- North American Bird Conservation Initiative, U.S. Committee. 2014. State of the Birds 2014 Report. U.S. Department of Interior, Washington, DC.
- Partners in Flight. 2012. Species assessment database.
- USGS Patuxent Wildlife Research Center. 2015. Longevity records of North American Birds.