Coevolution of acoustical communication between obligate avian brood parasites and their hosts

The mutually antagonistic processes producing adaptations and counter-adaptations in avian brood parasites and their hosts provide a model system for the study of coevolution; this topic has long been an area of focus in ornithology and evolutionary biology. Although there is an extensive body of literature dealing with avian brood parasitism, few empirical studies have considered the effects of the coevolutionary processes associated with brood parasitism on the acoustic characteristics of parent–offspring communication. Under the strong selection pressures associated with brood parasitism, parasitic birds may, for instance, produce deceptive songs. The host may in turn evolve the ability to recognize these sounds as deceptive. At present, the mechanisms underlying the different competitive strategies employed by hosts and parasitic birds remain unclear. Here, we reviewed previous studies that investigated acoustic traits in scenarios of brood parasitism, highlighting possible adaptive functions. Using a meta-analysis, we identified no heterogeneity among studies of begging call adaptations in parasitic nestlings. However, our results may have been affected by the small number of applicable papers available for analysis. Our meta-analysis also suggested that studies of acoustic communication and transmission in adult hosts were highly heterogenous, suggesting that research methods were inconsistent among studies. Finally, we identified knowledge gaps and proposed several lines of future research.