Is microevolution the only emergency exit in a warming world? Temperature influences egg laying but not its underlying mechanisms in great tits

Highlights ► Temperature has a direct, causal, effect on timing of breeding in great tits. ► Temperature does however not influence the neuro-endocrine mechanisms underlying timing. ► This lack of responsiveness might constrain the adaptation to global warming. ► There is heritable genetic variation in timing of breeding and the underlying mechanisms. ► Microevolution might thus be the only way to adapt to a warming climate.