Summary
The Short-tailed Green Magpie
Cissa thalassina, a member of an Asian lineage of uniquely coloured corvids, is represented by two subspecies,
thalassina and
jefferyi, that occur on the islands of Java and Borneo, respectively. The distinct Javan nominate form is poorly described in the literature and next to nothing is published on its biology and occurrence in the wild. We here document the biology and distribution of this taxon based on hitherto unpublished historical data and on our own fieldwork. We also analyse vocal data of
jefferyi, thalassina and two other
Cissa species and show that
jefferyi and
thalassina are well-differentiated, and that
thalassina is bioacoustically more similar to another
Cissa species from the Asian mainland. We also demonstrate important and significant biometric differences between
jefferyi and
thalassina that may reflect divergent adaptations to the environment, as well as plumage differences that may serve signalling functions. Finally, the application of a novel species delimitation test [
Tobias et al. (2010)] to our data suggests that
jefferyi and
thalassina deserve to be classified as biological species because their phenotypic divergence exceeds that found in many sympatric species. The revised taxonomic status of Javan
thalassina invites a reconsideration of its threat status. Based on its restricted range, extreme rarity and threats by bird trapping and habitat destruction, we consider the Javan Green Magpie as globally Critically Endangered.
