The Long-tailed Skua nests on open mountain heath and tundra. The nest is a simple shallow scrape on a tussock or on dry ground, with no appreciable material. The female usually lays 2 eggs, which are incubated by both parents for about three weeks. In poor rodent years breeding may fail entirely or not take place at all, while good lemming years yield good numbers of young. The parents defend the nest aggressively against intruders.