How specialized is the plant–pollinator association betweenEucalyptus globulusssp.globulusand the swift parrotLathamus discolor?

The swift parrotLathamus discolor(Shaw) (Psittacidae) evolved from granivorous ancestors to become a specialized flower‐feeder in a monotypic genus. Its reproduction is dependent largely on flowers ofEucalyptus globulusLabill. ssp.globulus(Myrtaceae),the birds migrating to breed within the natural distribution of this tree. This paper investigates the extent to which this dependence ofL. discoloronE. globulusis mirrored by dependence of the tree on the bird. It was found thatL. discolorcarried significantly more eucalypt pollen within 22 mm of its bill tip than did the New Holland honeyeater,Phylidonyris novaehollandiae(Latham) (Meliphagidae), and that pollen was concentrated on the regions of the head ofL. discolorthat consistently contact stigmas. Larger pollen loads onL. discolorcan be attributed to it consuming both pollen and nectar, while honeyeaters take nectar only. The short thick bill ofL. discolornecessitates regular stigmatic contact while the long slender bills of honeyeaters are unlikely to contact stigmas as often in these bowl‐shaped flowers. These factors suggest thatL. discolorhas a greater capacity to deposit pollen on stigmas ofE. globulusthan do honeyeaters. However, the characteristics ofL. discolorthat make it such an effective pollinator ofE. globulusare also exhibited by a lorikeet (Psittacidae) that feeds on flowers ofE. globulus. The association betweenE. globulusandL. discoloris therefore only moderately specialized because the flowers are also adapted to the more recently associated lorikeet and are almost certainly also pollinated by honeyeaters.