Guillemots breed in densely packed cliff colonies where individual welfare depends on food availability, storm weather, and freedom from disturbance during the sensitive breeding season.
Guillemot welfare during the breeding season is critically dependent on abundant food in adjacent seas, particularly sand eels and sprats for chick provisioning. Mass breeding failures in years of poor sand eel availability cause widespread chick starvation. Adults must travel increasingly far to find food as climate change shifts prey distributions, increasing energy expenditure and reducing time for incubation and brooding. Boat disturbance at cliff colonies causes panic flights that knock uncovered eggs and unfledged chicks from ledges to their deaths.