Avian brood parasites, species assemblage, and bird diversity: A case study using a grid-based survey in South Korea

Identifying proper surrogate species or groups is a challenging but critical step in the application of surrogate species approaches in biodiversity conservation because their effectiveness can vary according to biological communities. Recently, the brood parasitic common cuckoo, Cuculus canorus, has been suggested as a surrogate for describing biodiversity, primarily based on its strong parasitic relationship with other host species. However, the efficiency of cuckoo surrogates has been challenged because of the potential limitations of the methodo-logical approaches. Furthermore, its generality rarely has been explicitly tested in other parasitic species with local biodiversity data collected through conventional schemes such as grid-based sampling. Using bird survey data obtained from a grid-based sampling scheme in South Korea, we evaluated the surrogate efficiency of five cuckoo species for bird diversity (species richness and phylogenetic diversity) and generated surrogate species groups. We found that among the five parasitic cuckoo species breeding in South Korea, the common cuckoo and the Indian cuckoo C. micropterus were effective surrogate species. Among these, only the common cuckoo belonged to the best surrogate species group together with its major host species; the Indian cuckoo showed less effective surrogate efficiency than the common cuckoo. In conclusion, our study shows that the common cuckoo, as a single species and a member of a species assemblage, is an effective indicator species for bird diversity in grid-based survey data. However, the result that not all parasitic cuckoo species performed a surrogate role effectively implies that multiple functions may be associated with the surrogate efficiency of brood parasitic cuckoos, along with the importance of host-parasite relationships.