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Tengmalm’s Owl (Aegolius funereus)

Generally speaking owls prefer rather open woodland in which to hunt, as opposed to dense forest, with plenty of glades and edges rather than closed canopy, but the Tengmalm’s Owl is an exception to this, being equally efficient in both environments. In fact, in summer it is an advantage to hunt in deep forests, because the lack of light restricts the vegetation cover under which prey can hide, making it more vulnerable.

The Tengmalm’s Owl is found mainly in the boreal coniferous forest belt, being especially common in stands of spruce. It will, however, also breed in mixed woodland, especially with beech trees. It is a nocturnal species with exceptionally good hearing, aided by having asymmetrical ear openings which permit the detection of sound in both the vertical as well as horizontal plane; it is almost certainly able to hunt in complete darkness. It is very much of the “perch and pounce” school of hunting, and observations have revealed that, even when it has detected prey, the owl will only make a strike once the meal is out in the open. Its favourite food items are – inevitably for an owl – voles, although it will catch birds and insects, too.

Many Tengmalm’s Owls breed in the far north of Europe, and for those that remain during the winter food may be unpredictable in its appearance. For this reason the birds may cache food in holes and nestboxes when they have a good day, with up to 7 items recorded. In the prevailing cold climate cached prey often freezes, and when this happens a hungry Tengmalm’s Owl might have to sit upon its next meal, as if incubating it, in order to defrost it first for consumption.

Males are more willing to sit out the winters than females – they are probably under more pressure to hold on to their territories, whilst the females or young birds have only their own survival to think about. Those that migrate often lead a nomadic lifestyle in search of prey, and it then becomes doubtful that they will meet up with the same partner the following spring. On the contrary, female Tengmalm’s Owls have been known to breed in one season 680 km away from where they were in the previous one. In fact, relationships in this species of owl are much more fluid than most. Both males and females may have more than one mate; the latter, indeed, may lay two clutches of eggs in a season, each fathered by a different male.

In many parts of its range the Tengmalm’s Owl was once heavily reliant on the excavations of Black Woodpeckers for its nest holes. Now, though, it often uses nest-boxes instead.