The northern hawk-owl generally starts its mating rituals at the beginning of March. After calling and pairing is complete the northern hawk-owl will build a nest and start to lay eggs. On average the northern hawk-owl will lay 3–11 eggs per brood. The nest sites are usually the tops of hollow stumps of old dead spruce trees. These nesting sites are usually above ground for the North American "S. u. caparoch" and approximately above ground for the Eurasian "S. u. ulala". The specific dates of egg appearance can be quite variable depending on locality. In central Canada eggs are usually laid from March 30 to the 5th of June. On Newfoundland the appearance of eggs occurs later, between May 9 and June 11. In Finland however, eggs can be found anywhere between the 30th of March to the 23rd of June.