Belgium is known for two species of owls that nest and breed in Wallonia. However, aside from their preference for the French-speaking parts of the country and the same springtime breeding season, Tengmalm’s Owl and the Eagle Owl have little in common.
Tengmalm’s Owl (Aegolius funereus) is a small nocturnal bird. Males reach up to 24-26 cm (10 in) and weight around 100 g (0,22 lb). As a rule, these owls inhabit coniferous forests (mixed with leaf trees) covering the low mountain areas. For breeding, they choose boreal zones and alpine forests. Hence, the best place to observe Tengmalm’s Owl is Wallonia, namely—the Ardennes. The highest chances of an encounter with the owl are high in the province of Liege. Deep forests surround the municipalities of Stavelot and Trois-Ponts (especially the villages of Wanne and Logbiermé). In March, these areas give shelter to hundreds of Tengmalm’s Owls.
Meanwhile, the Eagle Owl (Bubo bubo) prefers to breed in the valley of the Meuse River instead of the dense forests of the Ardennes. This owl is much bigger than Tengmalm’s: males may reach up to 65 cm (25,6 in) and weight up to 3 kg (6,6 lb). During spring, Eagle Owls occupy quarries along the Meuse River to nest and breed. Notably, the owls choose not only both abandoned quarries but also those that are still working.
Generally, the nesting and breeding season for both may start as early as February and end as late as July, but the best time is between March and May/June.