Tengmalm's owl is a small owl, slightly larger than the Little Owl, and with a large rectangular head. Tengmalm's owl has a striking face, with a large whitish-grey facial disc ringed with a black border, large yellow eyes and a distinctively startled or surprised expression. The upperparts are dull brown with a profusion of whitish spots, with finer spotting on the crown and whitish underparts with warm vinous-brown blotches arranged in stripes.
Tengmalm's owl is a very rare vagrant in Britain, but there are small and discreet populations in mountainous forested areas in many European countries. Tengmalm's owl is most frequently found in the boreal forests of Scandinavia and Russia, and these northern populations occasionally irrupt southwards after a good vole year. Found in mature coniferous forest with small clearings and bogs, particularly in spruce, it is rather dependent on Black Woodpecker holes for nesting, although it can be found in plantations and secondary woodland where nest boxes are provided.
The advertising call of the Tengmalm's Owl Bird (male) is a repetitive short deep hoot, audible up to 2km range, "op'up'up' up'up'up'up'up'...", sung in the run-up to the breeding season from January to April, although unmated birds can call into July. Tengmalm's Owl bird is usually heard at night but occasionally also during the day. The call typically lasts for just 6-8 syllables, but can be much longer depending on the bird's state of excitement, and rises and falls in pitch through the course of the whole sequence. The most frequently heard call is a short "chi-ak" and a yelping "ku'waik", not unlike that of the Tawny Owl, plus a softer "awr'ehh". The young call with a short, rasping "pjjeh".