Morpho-functional analysis of the jaw apparatus of Vietnamese Passerine birds (Passeriformes): inferences on their trophic adaptations, ecology, and systematic position

The biology of many forest birds of Southeast Asia is still poorly known and requires extensive and intensive field study. Field data on trophic features of forest Passerine birds were collected in more than 15 forest areas in all main natural zones of the country during an ecological research program at the Russian-Vietnamese Tropical Research Centre in Vietnam in 1989–2013. The morpho-functional analysis of the jaw apparatus has been used to interpret field observations and to infer certain aspects of the feeding biology in the absence of direct observations. The analytical method comprises a detailed description of the morphology and a subsequent biomechanical analysis of the jaw apparatus as a basis for the reconstruction of the evolution of trophic adaptations in selected species and groups. A comparison of several congeneric species provided insights into the feeding adaptations in several genera of bulbuls and timaliid species and of several other Passerine families. Besides data on 16 picnonotid species and 11 timaliid species, data on selected representatives of Corvidae, Rhipiduridae, Oriolidae, Campephagidae, Dicruridae, Chloropseidae, Irenidae, Monarchidae, Aegithinidae, Dicaeidae, Nectarinidae, Sturnidae, Muscicapidae, and Zosteropidae were collected to identify their trophic adaptations. Our morpho-functional data show various degrees of specialization for different trophic strategies, such as insectivory, frugivory, nectarivory, predation, seed-eating, or eating of other plant matter. Several conclusions on the systematics of Old World Passerines based on these data are also presented.