Rapid behavioural response of urban birds to COVID-19 lockdown

Abstract

Biodiversity is threatened by the growth of urban areas. However, it is still poorly understood how animals can cope with and adapt to these rapid and dramatic transformations of natural environments. The COVID-19 pandemic provides us with a unique opportunity to unveil the mechanisms involved in this process. Lockdown measures imposed in most countries are causing an unprecedented reduction of human activities, giving us an experimental setting to assess the effects of our lifestyle on biodiversity. We studied the birds' response to the population lockdown by using more than 126 000 bird records collected by a citizen science project in northeastern Spain. We compared the occurrence and detectability of birds during the spring 2020 lockdown with baseline data from previous years in the same urban areas and dates. We found that birds did not increase their probability of occurrence in urban areas during the lockdown, refuting the hypothesis that nature has recovered its space in human-emptied urban areas. However, we found an increase in bird detectability, especially during early morning, suggesting a rapid change in the birds' daily routines in response to quieter and less crowded cities. Therefore, urban birds show high behavioural plasticity to rapidly adjust to novel environmental conditions, such as those imposed by the COVID-19.

Keywords: behavioural plasticity; citizen science; coronavirus disease; detectability; urban ecology.

Figure 1.

Probability of occurrence of birds in urban areas before (2015–2019, black dots) and during (2020; white dots) the COVID-19 lockdown. Asterisks indicate significant differences (p-value < 0.05). Error bars denote 95% confidence intervals. Acronyms for the species: Carcar Carduelis carduelis, Chlchl Chloris chloris, Colliv Columba livia, Colpal Columba palumbus, Cyacae Cyanistes caeruleus, Larmic Larus michahellis, Motalb Motacilla alba, Myimon Myiopsitta monachus, Parmaj Parus major, Pasdom Passer domesticus, Phooch Phoenicurus ochruros, Picpic Pica pica, Serser Serinus serinus, Strdec Streptopelia decaocto, Stuspp Sturnus spp., Turmer Turdus merula. (Online version in colour.)

Figure 2.

Variation in the probability of detection along the day for each group of data (collected during the lockdown, collected historically in urban sites and collected in non-urban environments). Shaded areas represent the 95% confidence intervals. See figure S2 in the electronic supplementary material for the rest of species. Bird illustrations by Martí Franch/Catalan Ornithological Institute. (Online version in colour.)

Figure 3.

Probability of detection in urban environments at sunrise for the 16 studied bird species before (2015–2019) and during (2020) the COVID-19 lockdown.