At a study site in southern Taiwan, Plain Flowerpeckers fed mainly on nectar and fruit of Taxillus pseudochinensis and dispersed the seeds of several mistletoes. The Taiwanese subspecies is described with a thin, pointed bill and pale underparts.
The Taiwanese subspecies uchidai is described as having a thin, pointed bill and light yellow to light green underparts.
In a study at Hengchun Tropical Botanical Garden, the birds fed mainly on nectar and fruit of Taxillus pseudochinensis and effectively dispersed seeds of three mistletoe species.
An extinction-risk assessment has not been added yet.