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Adaptation to proximity of humans should be particularly advantageous during adverse environmental conditions because the ability to withstand proximity to humans allows for exploitation of abundant food. We carried out flight initiation distance experiments in 207 bird species in 7 pairs of urban–rural areas from northern to southern Europe before and after the extremely cold winter of 2009–2010. Flight initiation distance in different species of birds on average became shorter after the cold winter, but only in resident urban populations (frequently exposed to humans) and not in migratory or rural populations of the same species. There were independent partial effects of human population density with an increase in flight initiation distance from before to after the cold winter of 2009–2010 at low population densities and a decrease at high population densities, and there was an independent effect of latitude …