BACKGROUND: Urban environments exert strong pressures on animal behavior, leading to altered fear responses to humans. Species with a longer history of urban presence and greater tolerance to urban environments are expected to show reduced fear responses towards humans. Here, we examined whether avian flight initiation distance (a proxy of fear)-the distance at which a bird flees from an approaching human-is associated with a species' timing of urban colonization (i.e., when it has started to breed in urban areas) and with present-day urban tolerance (i.e., how common it is in the city). Unlike previous studies which paired avian fear responses and urbanization timing from different regions, we collected both in the same city (Prague, Czechia), minimizing regional differences in urban history and providing a more rigorous test of the link between urbanization timing and avian fear responses. RESULTS: Using standardized data from 4420 flight initiation distance observations across 68 species, we applied Bayesian phylogenetic mixed models while controlling for ecological and contextual variables. We found that species with a longer urban history (i.e., earlier timing of urban colonization) showed significantly shorter flight initiation distances, suggesting reduced fear responses. In contrast, present-day urban tolerance based on breeding commonness was not related to flight initiation distance variation. CONCLUSIONS: We found that the timing of urban colonization better predicts reduced fear of humans in birds than present-day urban tolerance, emphasizing the role of long-term behavioral filtering and/or selection in shaping urban wildlife behavior. By explicitly separating urbanization time from contemporary urban commonness within a single city and analyzing individual-level fear responses, our study shows that earlier urban colonizers exhibit consistently shorter escape distances, reflecting cumulative long-term processes rather than short-term plasticity alone. These findings highlight the importance of incorporating urban colonization history into behavioral ecology and urban wildlife management frameworks.

• Keywords
• Birds, Flight initiation distance, Monitoring, Urban habitats, Urban tolerance, Urbanization time,
• MeSH
• Bayes Theorem MeSH
• Time Factors MeSH
• Flight, Animal MeSH
• Humans MeSH
• Birds * physiology   MeSH
• Fear * MeSH
• Urbanization * MeSH
• Cities MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic MeSH
• Cities MeSH

The coronavirus disease 2019 (COVID-19) pandemic and respective shutdowns dramatically altered human activities, potentially changing human pressures on urban-dwelling animals. Here, we use such COVID-19-induced variation in human presence to evaluate, across multiple temporal scales, how urban birds from five countries changed their tolerance towards humans, measured as escape distance. We collected 6369 escape responses for 147 species and found that human numbers in parks at a given hour, day, week or year (before and during shutdowns) had a little effect on birds' escape distances. All effects centered around zero, except for the actual human numbers during escape trial (hourly scale) that correlated negatively, albeit weakly, with escape distance. The results were similar across countries and most species. Our results highlight the resilience of birds to changes in human numbers on multiple temporal scales, the complexities of linking animal fear responses to human behavior, and the challenge of quantifying both simultaneously in situ.

• MeSH
• COVID-19 * epidemiology   MeSH
• Humans MeSH
• Pandemics MeSH
• Birds * virology   MeSH
• SARS-CoV-2 * MeSH
• Fear MeSH
• Escape Reaction MeSH
• Cities MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Cities MeSH

Animal tolerance towards humans can be a key factor facilitating wildlife-human coexistence, yet traits predicting its direction and magnitude across tropical animals are poorly known. Using 10,249 observations for 842 bird species inhabiting open tropical ecosystems in Africa, South America, and Australia, we find that avian tolerance towards humans was lower (i.e., escape distance was longer) in rural rather than urban populations and in populations exposed to lower human disturbance (measured as human footprint index). In addition, larger species and species with larger clutches and enhanced flight ability are less tolerant to human approaches and escape distances increase when birds were approached during the wet season compared to the dry season and from longer starting distances. Identification of key factors affecting animal tolerance towards humans across large spatial and taxonomic scales may help us to better understand and predict the patterns of species distributions in the Anthropocene.

• MeSH
• Behavior, Animal * MeSH
• Animals, Wild * physiology   psychology   MeSH
• Ecosystem * MeSH
• Human-Animal Interaction * MeSH
• Humans MeSH
• Urban Population MeSH
• Birds * physiology   MeSH
• Tropical Climate MeSH
• Rural Population MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Africa MeSH
• Australia MeSH
• South America MeSH

Actions taken against the COVID-19 pandemic have dramatically affected many aspects of human activity, giving us a unique opportunity to study how wildlife responds to the human-induced rapid environmental changes. The wearing of face masks, widely adopted to prevent pathogen transmission, represents a novel element in many parts of the world where wearing a face mask was rare before the COVID-19 outbreak. During September 2020-March 2021, we conducted large-scale multi-species field experiments to evaluate whether face mask-use in public places elicits a behavioural response in birds by comparing their escape and alert responses when approached by a researcher with or without a face mask in four European countries (Czech Republic, Finland, Hungary, and Poland) and Israel. We also tested whether these patterns differed between urban and rural sites. We employed Bayesian generalized linear mixed models (with phylogeny and site as random factors) controlling for a suite of covariates and found no association between the face mask-wear and flight initiation distance, alert distance, and fly-away distance, respectively, neither in urban nor in rural birds. However, we found that all three distances were strongly and consistently associated with habitat type and starting distance, with birds showing earlier escape and alert behaviour and longer distances fled when approached in rural than in urban habitats and from longer initial distances. Our results indicate that wearing face masks did not trigger observable changes in antipredator behaviour across the Western Palearctic birds, and our data did not support the role of habituation in explaining this pattern.

• Keywords
• Antipredator behaviour, Escape distance, Habituation, Human-induced rapid environmental change, Urbanization,
• MeSH
• Bayes Theorem MeSH
• COVID-19 * MeSH
• Humans MeSH
• Masks * MeSH
• Pandemics MeSH
• Birds MeSH
• SARS-CoV-2 MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Flight initiation distance (FID), the distance at which individuals take flight when approached by a potential (human) predator, is a tool for understanding predator-prey interactions. Among the factors affecting FID, tests of effects of group size (i.e., number of potential prey) on FID have yielded contrasting results. Group size or flock size could either affect FID negatively (i.e., the dilution effect caused by the presence of many individuals) or positively (i.e., increased vigilance due to more eyes scanning for predators). These effects may be associated with gregarious species, because such species should be better adapted to exploiting information from other individuals in the group than nongregarious species. Sociality may explain why earlier findings on group size versus FID have yielded different conclusions. Here, we analyzed how flock size affected bird FID in eight European countries. A phylogenetic generalized least square regression model was used to investigate changes in escape behavior of bird species in relation to number of individuals in the flock, starting distance, diet, latitude, and type of habitat. Flock size of different bird species influenced how species responded to perceived threats. We found that gregarious birds reacted to a potential predator earlier (longer FID) when aggregated in large flocks. These results support a higher vigilance arising from many eyes scanning in birds, suggesting that sociality may be a key factor in the evolution of antipredator behavior both in urban and rural areas. Finally, future studies comparing FID must pay explicit attention to the number of individuals in flocks of gregarious species.

• Keywords
• FID, birds, dilution effect, fear response, gregariousness, human disturbance, social interactions, vigilance,
• Publication type
• Journal Article MeSH