OPEN FORESTS On the softer sandstones and shales of the Terrigal Formation SOILS in open forests are more fertile giving a vegetation of eucalypts, angophoras and a shrub understorey. BIRDS in open forests include whistlers, wattlebirds, lorikeets, bellbirds, butcherbirds, magpies, noisy miners, tawny frogmouths, glossy black cockatoos and parrots.