Lockdown effects on fear revealed direct and indirect effects of human presence on perceived predation risk

The Covid-19 lockdown reduced drastically human presence outdoors, providing an uncontrolled experiment for disentangling direct and indirect effects of human presence on animal fearfulness. We measured 18,494 flight initia-tion distances (FIDs, the distance at which individual animals fly away when approached by a human) from 1333 pop-ulations of 202 bird species taken in four European cities both before, during and after the lockdown. FIDs decreased during lockdown in rural habitats but increased in urban habitats, especially for singing birds. Height above ground increases during lockdown in non-singing birds only, and birds adjusted horizontal tolerance to approach according to height outside lockdown, in rural habitats and while not singing. Responses showed lagged effects after lockdown in urban but not in rural habitats. Differential responses to lockdown among habitats and between signing and non -singing birds were consistent with relaxation of direct disturbance effects on birds in rural habitats during lockdown, as well as with increased indirect fear effects mediated by predator release in cities. FIDs seemed to measure the balance of direct and indirect effects of humans on predations risk and food needs rather than direct effects of humans on fear.

Automated summary

The Covid-19 lockdown provided an opportunity to study the direct and indirect effects of human presence on animal fearfulness. Flight initiation distances (FIDs) of birds were measured in European cities before, during, and after the lockdown. FIDs decreased in rural habitats but increased in urban habitats, especially for singing birds. The response to lockdown showed lagged effects in urban habitats but not in rural habitats. These findings suggest that the relaxation of direct disturbance effects in rural habitats and increased indirect fear effects mediated by predator release in cities influenced the flight behavior of birds.