Two species of Orphean Warblers Sylvia hortensis, S. crassirostris in Croatia: data overview and implications for future research

Orphean Warblers Sylvia hortensis and S. crassirostris are two similar species that have recently been split from a single species complex. It is considered that only S. crassirostris breeds in Croatia. The data collected on this species in Croatia, however, is inconsistent as some ornithologists still use either name. In order to discern whether both species oc-cur in Croatia, I conducted a study of citizen science data and a review of skins in three museum collections. There was a specimen of S. hortensis in the collection of the Institute of Ornithology, collected on the island of Brač in 1964. Citizen science data yielded no verifiable observations of S. hortensis in Croatia. Bill length was an unreliable distinction characteristic between the two species, while plumage characteristics proved useful only for adult birds. Reliable distinction characteristics are thus song, tail and moult pattern and mt-DNA. Detailed studies of Orphean Warblers’ distribution and characteristics in Croatia and Italy are recommended.