Rural-Urban Differences in Escape Behavior of European Birds across a Latitudinal Gradient

Abstract

Behavioral adjustment is a key factor that facilitates species' coexistence with humans in a rapidly urbanizing world. Because urban animals often experience reduced predation risk compared to their rural counterparts, and because escape behavior is energetically costly, we expect that urban environments will select for increased tolerance to humans. Many studies have supported this expectation by demonstrating that urban birds have reduced flight initiation distance (FID = predator-prey distance when escape by the prey begins) than rural birds. Here, we advanced this approach and, for the first time, assessed how 32 species of birds, found in 92 paired urban-rural populations, along a 3,900 km latitudinal gradient across Europe, changed their predation risk assessment and escape strategy as a function of living in urban areas. We found that urban birds took longer than rural birds to be alerted to human approaches, and urban birds tolerated closer human approach than rural birds. While both rural and urban populations took longer to become aware of an approaching human as latitude increased, this behavioral change with latitude is more intense in urban birds (for a given unit of latitude, urban birds increased their pre-detection distance more than rural birds). We also found that as mean alert distance was shorter, urban birds escaped more quickly from approaching humans, but there was no such a relationship in rural populations. Although, both rural and urban populations tended to escape more quickly as latitude increased, urban birds delayed their escape more at low latitudes when compared with rural birds. These results suggest that urban birds in Europe live under lower predation risk than their rural counterparts. Furthermore, the Samia et al.Rural-Urban Difference in Escape Behavior patterns found in our study indicate that birds prioritize the reduction of on-going monitoring costs when predation risk is low. We conclude that splitting escape variables into constituent components may provide additional and complementary information on the underlying causes of escape. This new approach is essential for understanding, predicting, and managing wildlife in a rapidly urbanizing world.

Contagious fear: Escape behavior increases with flock size in European gregarious birds

“…Data were collected during the breeding period in each study area (April-September 2015) using a standard protocol (Blumstein, 2006;Samia et al, 2017) in urban and adjacent rural areas of eight cities in eight European countries: Czech Republic, Denmark, Estonia, Finland, France, Hungary, Poland, and Spain ( Figure 1; Table S1). …”

“…We used a study design collecting data in urban and rural sites (habitat type) in each study location, because a large amount of literature highlights the main differences between urban and rural environments, in terms of responses of birds to risk of predation (Møller, 2012;Møller et al, 2013;Samia et al, 2017;Sol et al, 2018).…”

“…Many studies of escape behavior in birds focused on the influence of external factors affecting behavioral responses: habitat quality (Burger, Gochfeld, Jenkins, & Lesser, 2010), the direction of approach by predators (Møller & Tryjanowski, 2014), intruder starting distance (Blumstein, 2013;Glover et al, 2011), number or density of intruders (Geist, Liao, Libby, & Blumstein, 2001), population density (Mikula, 2014), urbanization (Samia et al, 2017), road speed limits (Legagneux & Ducatez, 2013), insular distribution (Cooper, Pyron, & Garland, 2014), predator-prey interactions (Møller, 2008b), spatial gradients of predator abundance (Díaz et al, 2013), or daytime and season when FID was measured (Burger & Gochfeld, 1991;Piratelli, Favoretto, & de Almeida Maximiano, 2015). Blumstein (2006) has made links between escape behavior and life history and natural history traits (e.g., diet) in birds.…”

“…Additionally, we know that behavioral responses of animals to human approach such as FID can be useful for conservation purposes, namely management of disturbance, especially in human-dominated environments (Guay, Dongen, Robinson, Blumstein, & Weston, 2016;Weston et al, 2012). Group size has been suggested to be another important component that influences escape decisions by prey (Burger & Gochfeld, 1991;Fernández-Juricic, Jimenez, & Lucas, 2002;Glover et al, 2011;Samia et al, 2017;Yasué, 2005). Group size has been suggested to be another important component that influences escape decisions by prey (Burger & Gochfeld, 1991;Fernández-Juricic, Jimenez, & Lucas, 2002;Glover et al, 2011;Samia et al, 2017;Yasué, 2005).…”

“…We explored differences in FID between environments because previous studies suggested significant differences between urban and rural birds (Díaz et al, 2013;Piratelli et al, 2015;Samia et al, 2017). The ecological rationale for this expectation is that vigilance and FID increase with group size because of the many eyes effect, and vigilance can be transmitted more easily (or quickly) when there are many individuals in a flock.…”