Great tits take greater risk toward humans and sparrowhawks in urban habitats than in forests

Abstract

Urban animals often take more risk toward humans than their non‐urban conspecifics do, but it is unclear how urbanization affects behavior toward non‐human predators. Responses to humans and non‐human predators may covary due to common mechanisms enforcing a phenotypic correlation. However, while increased tolerance toward humans may be advantageous for urban animals, reduced vigilance toward non‐human predators that can pose actual threat may be costly. Therefore, urban animals may benefit from showing specific responses to different threat levels, such as humans versus non‐human predators, or hostile versus non‐hostile humans. To test these alternatives, we compared responses (latencies to return to nest) of urban and forest‐breeding great tits (Parus major) to familiar hostile and unfamiliar humans as well as one of their common predators, the sparrowhawk (Accipiter nisus). We found that urban birds were more risk‐taking toward both humans and sparrowhawk than forest birds. However, responses to sparrowhawk did not correlate with responses to humans either within or across habitats. This suggests that higher risk‐taking of urban compared to forest‐dwelling great tits toward sparrowhawk may be threat‐specific response to lower predation risk rather than a spillover effect of increased tolerance to humans. Furthermore, birds responded similarly to unfamiliar and familiar (potentially dangerous) humans in both habitats, suggesting that great tits may not adjust their risk‐taking to the threat represented by individual humans. These findings indicate that urban birds may flexibly adjust their risk‐taking to certain, but not all, types of threat.

Urban fox squirrels exhibit tolerance to humans but respond to stimuli from natural predators

“…For example, Cooper et al (2008) showed that gray squirrels (Sciurus carolinensis) in urban areas exhibited a lower FAD when exposed to a human with a leashed dog versus just a human, whereas the crosshabituation due to human stimuli hypothesis would predict that squirrels in urban areas would exhibit a similar FAD when exposed to humans or humans with a dog. Previous studies (see also Labra and Leonard, 1999;Seress et al, 2011;Bokony et al, 2012;Cavalli et al, 2016;Weaver et al, 2018;Vincze et al 2019) together with our results support that animals in urban habitats or those frequently exposed to humans, even if habituated to humans, still exhibit increases in antipredator behavior in response to a non-human predator.…”

“…If animals do not exhibit enhanced vigilance or increased FID to a human observer that is paired to some stimulus from a natural predator compared to if they were approached by a human without such a stimulus, this supports the hypothesis that animals do not view the situation as risky due to the presence of a human (i.e., they exhibit cross-habituation). We call this the "cross-habituation due to human stimuli" hypothesis given the long precedent of studies in experimental psychology examining crosshabituation (Hinde, 1954), although we note that this type of cross-habituation has also been termed "human-mediated behavioral spillover" (Geffroy et al, 2015) or "transfer habituation" (Coleman et al, 2008;McCleery, 2009) and examines similar phenomenon as the "threatspecific risk-taking" and "general risk-taking" hypotheses, with the latter predicting that urban animals take more risks in the presence of both humans and non-human natural predators (Vincze et al, 2019).…”

Does offspring sex ratio differ between urban and forest populations of great tits (Parus major)?

“…To statistically compare the sex ratios between the two habitat types (urban sites vs. forest sites) we calculated linear contrasts from the full and reduced models. These linear contrasts were pre-planned comparisons between the two urban sites vs. the two forest sites (see also Pipoly et al 2019 and Vincze et al 2019 for the same approach to compare habitat types by pre-planned linear contrasts and for additional details of the method). Each linear contrast was back-transformed from the log-scale to provide the odds ratio (OR, i.e.…”

Biologia Futura: adaptive changes in urban populations

“…Thus, whether and how urbanization influences predation risk is likely specific for a given predator-prey system, and also can vary between cities. For example, urban house sparrows and great tits from the same geographic areas showed stronger and weaker responses, respectively, to experimental exposure to sparrowhawk (Accipiter nisus, one of their most common predators) than their non-urban conspecifics, suggesting contrasting urban predation risk for these species (Seress et al 2011;Vincze et al 2019).…”