Morphological adaptations to nectarivory of the alimentary tract of the Swift Parrot Lathamus discolor

The morphology and microscopic architecture of the alimentary tract of the Swift Parrot was compared to that of the Green Rosella and Musk Lorikeet. Gut contents were evaluated grossly and by light microscopic examination. There were significant differences between the Swift Parrot and the Green Rosella in the scaled measurements of the length of the distal oesophagus and proventriculus and in the width of the crop, duodenum, intestine and cloaca. There were significant differences in the scaled measurements of the length of the gizzard and the width of the oesophagus, gizzard and duodenum between the Swift Parrot and the Musk Lorikeet. The results support previous findings that the Swift Parrot has retained some of the alimentary features of its granivorous ancestors. However, our findings suggest that the Swift Parrot may have adapted to nectarivory, not only with the development of a brush tongue, but also in changes to the crop, proventriculus and duodenum. The larger, more muscular gizzard and longer intestine may allow the Swift Parrot to use a diversity of dietary items when nectar and pollen are not readily available.