Intimacy across species boundaries: interspecific allopreening between Spot-necked (Stachyris strialata) and Nonggang Babblers (S. nonggangensis)

Allopreening occurs in many species of birds and is known for providing hygienic and social benefits. While this behavior has been studied between conspecifics, its occurrence among different species remains mysterious. Outside of captivity environment, only a few records of interspecific allopreening exist. In this study, we report the first documented record of a Spot-necked Babbler (Stachyris strialata) allopreening a Nonggang Babbler (Stachyris nonggangensis) in a non-captive environment in southern China. We provide three hypotheses (social dominance, cleaning mutualism, and hybridization) to explain the occurrence of this understudied behavior. We suggest that interspecific allopreening may not be as rare as we assumed if we are in the correct place to study it. This study contributes to our understanding of not only the potential mechanism(s) for interspecific allopreening but also the behavioral ecology of the vulnerable Nonggang Babbler.