Summary
The nesting of urban dark-eyed juncos was compared between 2019 (pre pandemic) and in 2021 (during the pandemic when human activity was reduced). The researchers also collected human foot traffic surveys in May-July 2021 and April-June 2022. In 2019 and 2021, a total of 164 and 117 junco nests were located and monitored respectively. In 2021, 38.5% of nests were off the ground, compared to 34.8% in 2019. 22.2% of nests were on artificial substrates in 2021, compared to 18.9% in 2019, with nests on artificial substrates having a positive impact on nest success compared to those on natural substrates. Overall, reduced human activity during the pandemic did not significantly change the nesting behaviors of juncos. Regarding limitations, the authors acknowledge, although they deem it unlikely, that due to the rapid changing of human activity insufficient time may have passed to see a difference in junco behavior. A strength in this study is the large sample size of nests observed. The authors highlight that COVID-19 provided an opportunity to examine the impact of human activity on wildlife, and in certain instances like this study, no direct effects were observed which reveals the need for further research to understand the extent of human disturbance on avian wildlife.
The COVID-19 pandemic temporarily transformed urban ecosystems by restricting public human activity to only the most essential societal functions, even as other landscape level factors such as the built environment remained unchanged. In so doing, it provided a unique opportunity to experimentally answer questions about the role of human disturbance in driving behavioural adaptation in urban wildlife. We compared nesting data collected on an urban dark-eyed junco, Junco hyemalis, population nesting on the University of California, Los Angeles (UCLA), U.S.A. campus during the 2021 nesting season, when the campus restrictions were in effect, to a similar data set collected in 2019, before the pandemic, in order to examine (1) whether urban dark-eyed juncos on the UCLA campus altered their use of novel off-ground and artificial nesting sites in response to reduced human activity and (2) whether reduced human activity impacted nesting success. We found that after a >80% reduction in human activity, junco nesting success during the COVID-19 pandemic modestly increased compared to prepandemic levels. However, nest site selection remained unchanged. Our findings suggest that the landscape of the built environment or urban predators, rather than disturbance by human activity, drives novel nest site selection in urban birds.