Tengmalm’s owl – Aegolius funereus
Boreal owl is a small owl. In Europe, it is typically known as Tengmalm’s owl after Swedish naturalist Peter Gustaf Tengmalm or, more rarely, Richardson’s owl after Sir John Richardson. The scientific name is from Latin. The genus name Aegolius is a type of screech owl thought to be a bird of ill omen, and funereus means “funereal”.

This species is a part of the larger grouping of owls known as typical owls, Strigidae, which contains most species of owl. The other grouping is the barn owls, Tytonidae. Due to its shyness and evasive reaction to human activities, nocturnal habits and preferred inaccessible taiga forest habitat, it ranks as one of the, if not the, least known owls in both North America and Europe.

The boreal owl is 22–27 cm (8.7–10.6 in) long with a 50–62 cm (20–24 in) wingspan. It is brown above, with white flecking on the shoulders. Underparts whitish streaked with rust. The head is large, with yellow eyes and a white facial disc, and a “surprised” appearance. The beak is light yellow colored rather than dark like its relative the northern saw-whet owl. The flight is strong and direct. Young birds are chocolate brown.

It sounds like this
Recording by Lars Edenius from Xeno canto