| Abstract: | Both birds and insects visit yellow flower heads of Banksia ilicifolia rather than those in the pink or red phases. Birds carry most pollen. Substantial nectar and pollen rewards are present only in the yellow phase. The timing of flower colour change also corresponds to a decline in viability of presented pollen and stigma receptivity. Colour change is age-dependent rather than pollinator-induced. Bird visits to yellow or red heads are essentially determined by the availability of nectar in each rather than differences in their visibility. Fruit set is negligible in the absence of pollinators but still < 1% in their presence. Banksia ilicifolia has the smallest heads and is the most localized of five co-occurring and partly co-flowering Banksia species. It is hypothesized that the restriction of flower colour change to B. ilicifolia increases the competitiveness of this species: bird visitors are directed to flower heads with abundant nectar, viable pollen and receptive stigmas, foraging and pollination efficiency thereby being enhanced without a marked reduction in long-distance attractiveness of the tree to potential pollinators. |
