A new and empty island initially has:
“High immigration and low extinction” for a new and empty island initially has. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. The remaining alternatives—“High extinction and low immigration”, “Low immigration and high extinction”, “Both high immigration and high extinction”—refer to different states, processes, or scales and therefore do not express the same causal relationship. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: Biogeography, Lomolino et al., 5th Ed., Ch. 1-4