The Alimentary-Tract of a Specialist Frugivore, the Mistletoebird, Dicaeum-Hirundinaceum, in Relation to Its Diet

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Abstract
The mistletoebird, Dicaeum hirundinaceum, is unique in Australia for its specialised diet of mistletoe berries. Like other frugivorous dicaeids it has a relatively short alimentary tract. Unlike insect-eating passerine birds, the proventriculus, gizzard and duodenum of dicaeids are all in the same plane, allowing rapid passage of the large numbers of berries consumed. The gizzards of frugivorous dicaeids are much smaller and less muscular than those of insectivorous birds of similar size from the same areas. There is, however, no evidence of a sphincter muscle controlling access to the gizzard, despite accounts of this in the literature.