European rollers are declining across their range due to loss of open hunting habitat, nesting cavities, and insect prey — with Spain and Portugal holding the largest remaining populations.
Rollers nesting in hollow trees face cavity eviction by nest competitors including starlings and jackdaws. Insecticide exposure through ingesting treated insects causes acute toxicity and sublethal effects on reproduction. Chicks raised in poor prey years are malnourished and face high mortality before autumn migration. Rollers are sensitive to agricultural intensification, and landscape-level prey reduction leaves birds unable to meet energetic demands during chick-rearing.