Nectar feeding beyond the tongue: hummingbirds drink using phase-shifted bill opening, flexible tongue flaps and wringing at the tips.

Hummingbirds are the most speciose group of vertebrate nectarivores and exhibit striking bill variation in association with their floral food sources. To explicitly link comparative feeding biomechanics to hummingbird ecology, deciphering how they move nectar from the tongue to the throat is as important as understanding how this liquid is collected. We employed synced, orthogonally positioned, high-speed cameras to describe the bill movements, and backlight filming to track tongue and nectar displacements intraorally.

Variable evidence for convergence in morphology and function across avian nectarivores.

Nectar-feeding birds provide an excellent system in which to examine form-function relationships over evolutionary time. There are many independent origins of nectarivory in birds, and nectar feeding is a lifestyle with many inherent biophysical constraints. We review the morphology and function of the feeding apparatus, the locomotor apparatus, and the digestive and renal systems across avian nectarivores with the goals of synthesizing available information and identifying the extent to which different aspects of anatomy have morphologically and functionally converged.

On the feeding biomechanics of nectarivorous birds.

Nectar-feeding birds employ unique mechanisms to collect minute liquid rewards hidden within floral structures. In recent years, techniques developed to study drinking mechanisms in hummingbirds have prepared the groundwork for investigating nectar feeding across birds. In most avian nectarivores, fluid intake mechanisms are understudied or simply unknown beyond hypotheses based on their morphological traits, such as their tongues, which are semi-tubular in sunbirds, frayed-tipped in honeyeaters and brush-tipped in lorikeets.