Abstract
The ubiquitous activity of humans is a fundamental feature of urban environments affecting local wildlife in several ways. Testing the influence of human disturbance would ideally need experimental approach, however, in cities, this is challenging at relevant spatial and temporal scales. Thus, to better understand the ecological effects of human activity, we exploited the opportunity that the city-wide lockdowns due to the COVID-19 pandemic provided during the spring of 2020. We assessed changes in reproductive success of great tits (Parus major) at two urban habitats affected strikingly differently by the ‘anthropause’, and at an unaffected forest site. Our results do not support that urban great tits benefited from reduced human mobility during the lockdown. First, at one of our urban sites, the strongly (− 44%) reduced human disturbance in 2020 (compared to a long-term reference period) did not increase birds’ reproductive output relative to the forest habitat where human disturbance was low in all years. Second, in the other urban habitat, recreational human activity considerably increased (+ 40%) during the lockdown and this was associated with strongly reduced nestling body size compared to the pre-COVID reference year. Analyses of other environmental factors (meteorological conditions, lockdown-induced changes in air pollution) suggest that these are not likely to explain our results. Our study supports that intensified human disturbance can have adverse fitness consequences in urban populations. It also highlights that a few months of ‘anthropause’ is not enough to counterweight the detrimental impacts of urbanization on local wildlife populations.
Highlights
The ubiquitous activity of humans is a fundamental feature of urban environments affecting local wildlife in several ways
Data on the birds’ reproductive success and the number of humans present at nest sites were collected as part of a long-term, ongoing monitoring project in Hungary, in which we investigate the impacts of urbanization on populations of great tits
Even though the two cities greatly differ in their size and human population, our urban study plots in both cities have similar general characteristics: these are surrounded by built-up areas, are at a similar distance (c. 3–4 km) from the nearest forested areas, and nests experienced a similar level of human disturbance in the pre-COVID reference period (Fig. 1b)
Summary
The ubiquitous activity of humans is a fundamental feature of urban environments affecting local wildlife in several ways. To impede the spreading of the coronavirus disease (COVID-19), many countries went into lockdown during the spring of 2020 This resulted in greatly reduced human mobility and traffic in cities and towns across the world for several months, a phenomenon recently coined as ‘anthropause’[5]. In the northern temperate zone, the duration of the lockdown coincided with the breeding season of many animal populations, providing excellent opportunities to investigate the fitness consequences of human activities in urban wildlife populations Under usual circumstances, these impacts are typically inferred from comparisons between populations living in habitats with different levels of urbanization or along urban-to-rural gradients[12], because conducting experiments on relevant spatial and temporal scales in cities is challenging (but see[13]). We have limited and mostly correlative evidence on the impacts of these anthropogenic effects on the fitness of urban animals
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