Soundscapes and anthromes: A review of proximate effects of traffic noise on avian vocalization and communication

Across anthromes there has been an increase in the number and miles of roadways with a corresponding increase in vehicle traffic. Roads and associated traffic and traffic noise has been shown to affect avian abundance, breeding success, density and species diversity. An expanding body of literature has demonstrated that many bird species alter the way they vocalize in order to be heard by conspecifics and other species in response to the noise generated by traffic and other human activity. This review summarizes the literature that describes the effects of traffic noise on birds across anthromes. Documented changes in vocalizations due to traffic noise include shifts in amplitude, frequency, rate, timing, and duration of vocalizations along with a number of behavioral adaptations. Costs of altering vocalizations include the inability to attract a mate, poor vocal performance, not sounding like conspecifics, and being more easily heard by predators. Outstanding research needs in this area include (1) controlling variables that might affect negative impacts on birds along roadways, (2) analyzing vocal communication during the non-breeding season, (3) identifying consequences of and responses to acoustic masking (e.g., inability to protect a territory or faulty parent-offspring communication), and (4) applying research to mitigation efforts.