LaManna, J. A., and T. E. Martin. 2015. Costs of fear: Behavioural and life-history responses to risk and their demographic consequences vary across species. Ecology Letters 19: 403–413.
Behavioral responses to reduce predation risk might cause demographic ‘costs of fear’. The rare tests in terrestrial systems have focused on single species, but differences in life histories and ecology among species could yield differing costs that need to be understood to develop a general framework. Thus, we used natural and experimental variation in predation risk to test phenotypic responses and associated demographic costs for 10 songbird species. Increases in risk generally yielded increased time spent incubating eggs, which caused shorter development periods that reduce nest mortality. Parents also fed offspring less often with increased risk, but offspring maintained growth of structures used to escape predators (wings, tarsi) while sacrificing mass growth. Reproductive output from non-depredated nests declined along risk gradients, but the severity of this cost varied across species. Ultimately, phenotypic responses to predation risk are common across co-occurring species, but responses and demographic costs vary substantially.