[Distinctive morphofunctional features of the bill and hyoid apparatus of turacos (Aves, Musophagidae): relations with frugivory]. / Les particularités morphofonctionnelles des appareils du bec et hyoïdien chez les touracos (Aves, Musophagidae): relations avec la frugivorie.

The present study points to morpho-anatomical features that allow vegetarian but mainly frugivorous turacos to fill at best their specific feeding requirements. Mechanisms are analysed which the bird can use to detach a fruit and avoid it rolls out of the bill. It is also examined how vegetable items can be processed particularly when they have to be cut, and what can facilitate their ingestion particularly when they are fruits that have to be swallowed entirely and are large and/or have dry or fibrous skin or flesh. The skeletal and muscular anatomy of the bill and hyoid apparatus is described in details and illustrated. The particularly short and stout bill coupled with a relatively simple system of aponevroses of the adductors reflects a trade-off between two important jaw functional requirements: huge efforts for clamping, and a wide opening for plucking, processing and swallowing relatively large fruit. The clearly oblique orientation of the modified outer adductor seems an adaptation to the detachment of fruits. The os uncinatum, particularly developed in this bird family, is interpreted as maintaining transversal stability, particularly when jaws act as a pair of scissors. Most food items being processed near the base of the bill, mechanisms have been developed which contribute to overcome the risk of breakage at the level of the prokinetic hinge because of a vertically oriented force there.

[Morphofunctional analysis and trophic adaptations: the case of bill apparatus of Old World flycatchers]. / Analyse morphofonctionnelle et adaptations trophiques: le cas de l'appareil du bec des gobe-mouches de l'Ancien Monde.

A morphofunctional analysis of the bill apparatus was conducted on some African forest flycatchers (Muscicapidae, Platysteiridae, Monarchidae) in relation to detailed eco-ethological data available on these species. The aim was to evaluate relationships between anatomical structures and habitat constraints and also identify the most pertinent trophic adaptations. If forest Muscicapidae have essentially conserved the generalized passerine structures and occupy open-habitat niches in the forest, Platysteiridae and Monarchidae have adapted to forest conditions and show a key-adaptation based on specific changes in the structure of the bill apparatus in response to particular light patterns and habitat clogginess, constraints that require speed and precision for the capture of prey and protection of the skull against collisions.