Inbreeding Threatens Norfolk Island Morepork Owls

In the 1980s the Norfolk Island morepork almost vanished, leaving only one breeding female. The entire current population traces back to that lone bird.

A male morepork from New Zealand was moved to the island in 1988. Norfolk Island science ranger Allie Andersen said the translocation raised the number of breeding pairs and the population grew to about 50 by the late 1990s.

By 2021 only about 25‑26 owls remain. Monash University ornithologist Rohan Clarke warned that reproduction has slowed and infertility is common because the birds are highly inbred. He added that the window for action may be measured in years.

High inbreeding reduces genetic diversity, which weakens fertility and the ability of the owls to produce healthy offspring. When only a few individuals contribute genes, each loss of an adult dramatically cuts the gene pool, pushing the species closer to extinction.

Scientists now suggest bringing genetically similar moreporks from New Zealand to increase diversity. The plan would involve careful biosecurity checks and consultation with local communities and Māori custodians before any new birds are released.

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