Song Characteristics of Oriental Cuckoo Cuculus optatus and Himalayan Cuckoo Cuculus saturatus and Implications for Distribution and Taxonomy.

Canwei Xia, Wei Liang, Geoff J. Carey, and Yanyun Zhang (2016) Song features during the breeding season are important in identifying species of cuckoos. Whether Oriental Cuckoo Cuculus optatus and Himalayan Cuckoo C. saturatus inhabiting the Palearctic and Oriental realms respectively can be distinguished according to song characteristics is uncertain. In this study, we performed a thorough investigation of the song characteristics of these taxa by collecting and analyzing recordings of song in their distribution areas. We found that songs could be divided into two groups based on the number of notes per syllable, and significant differences in other frequency and temporal features were also found between these two groups. The group with a song comprising two notes per syllable was shown to breed in Russia, Japan and China including Xinjiang, Inner Mongolia, Heilongjiang and Taiwan, while the group with a song containing more than two notes per syllable was found to breed in the Himalayas and central China, extending northeast through north China as far as northeast Hebei, and south to southwest China. The distribution of these two groups was broadly related to the published distribution of populations of optatus and saturatus, respectively. Our data supported the separation of optatus and saturatus based on their song features, and also suggested refinements to the distribution of these two taxa, as follows: birds in north mainland China are saturatus, and those in Taiwan Island are optatus.