title: On the structural adaptations of the bill, skull-elements, tongue, and hyoid of some Indian insect-eating birds.
abstract: The study of the functional morphology of the feeding apparatus of some Indian insect-eating birds reveals suitable adaptational changes in the structure of their bill, skull-elements, tongue, and byoid in different degrees, depending on the nature of their partial adaptation to secondary food-habits. The hooked tip of the upper beak in Muscicapa and Dicrurus, sharp tomial edges of both the beaks in Turdoides and the long, gradually curved bill in Merops are some of the suitable adaptations of the bill for food-getting. The dimensional variations of the skull and its kinetic elements may be correlated not only with the food-habits of birds studied, but also with the patterns of jaw and tongue muscles possessed by them. A comparatively greater width of the cranium and height of the lower jaw in Turdoides and Dicrurus provide wider areas for the origins and insertions of the adductor muscles. The skull in all the birds studied is pro-kinetic. The kinesis of the upper jaw, however, depends on several factors of which the angles of placement of the quadrate-pterygoid-palatine components, the nature of the naso-frontal hinge and the resultant "torques" produced by differential forces of muscles are very significant. The upper jaw kinesis is best developed in Merops and Orthotomus. The variations in the structure of the tongue and hyoid may also be correlated with various movements of the tongue in both primary and secondary food-adaptations.
mesh_terms: D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology*; D001502:Beak / Q000033:anatomy & histology*; D001717:Birds / Q000033:anatomy & histology*; D005247:Feeding Behavior / Q000502:physiology*; D006928:Hyoid Bone / Q000033:anatomy & histology*; D007194:India; D007313:Insecta; D011235:Predatory Behavior / Q000502:physiology*; D012886:Skull / Q000033:anatomy & histology*; D013045:Species Specificity; D014059:Tongue / Q000033:anatomy & histology*