Eucalyptus pollen grain emptying by two Australian nectarivorous psittacines

The relative importance of pollen as a source of protein to vertebrates is controversial. In nectarivorous psittacine birds, field studies support its importance, but an experimental study in a nectarivorous parrot showed that less than 7% of pollen grains were emptied. We investigated pollen grain emptying by two nectarivorous Australian parrots, the Swift Parrot Lathamus discolor and the Musk Lorikeet Glossopsitta concinna. We used a controlled experiment, and examined pollen located at different levels through the alimentary tract of wild L. discolor. There was significant emptying of pollen grains (x = 45.4%±1.91 s.e.) by all birds in the experimental trials. There was also a progressive increase in the percentage of pollen grains emptied at different sites along the alimentary tract in wild birds (crop x = 24.2%±4.44 s.e., proventriculus x = 34.0±7.29 s.e., duodenum x = 54.3%±5.42 s.e. and distal intestine x = 64.2%±4.68 s.e.). The percentage of pollen grains emptied by captive L. discolor in the experimental trial (x = 44.1%±2.77 s.e.) was not significantly different from that found in wild L. discolor (x = 40.3%±4.25 s.e.). Both species of nectarivorous parrot were able to rapidly ingest large quantities of Eucalyptus pollen and appeared to empty the pollen grains efficiently. Eucalyptus pollen appears to be an important source of protein for these birds.