[5] Scientists believe the two sister species are descended from a shared ancestor whose once widespread populations were separated by climate change.

[8] Females are smaller with olive-grey crown, similar in colouring to male but slightly duller; and juveniles are pale warm cinnamon below with grey to olive-brown upperparts, a brown-red eye and orange base to the bill.

The nest is a deep cup-shaped structure of grass and bark strips, lined with feathers and soft plant fibres, hanging by the rim in the fork of a small bushy tree or shrub, 1–15 m (3–49 ft) above ground.

The eastern spinebill feeds on nectar from many plants, including the blooms of gum trees, mistletoes Amyema spp., Epacris longiflora,[13] Epacris impressa (common heath), Correa reflexa, and various members of the Proteaceae such as Banksia ericifolia,[14] Banksia integrifolia, Lambertia formosa and Grevillea speciosa, as well as small insects and other invertebrates.

A 1982 study in the New England National Park in north-eastern New South Wales found that there was a large influx of birds coinciding with the start of flowering of Banksia spinulosa there.