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The return of burrow-nesting seabirds to Ipipiri

Early this month Jo Sim and her species conservation dog Rua spent five gruelling days surveying the rugged coastlines of Ipipiri in search of burrow-nesting seabirds. The forests of these islands would have once been abundant with burrows housing a myriad of seabird species, but due to the arrival of introduced mammals and changes in land-use, the seabird population has been much reduced.

New Zealand is seabird central, with our waters having the highest species richness of anywhere on the planet. In New Zealand we have an appalling record of mainland colonies being wiped out by introduced predators, but the ecology of many islands is still dominated by the positive effects of burrowing seabirds. Their activities alter nutrients in the soil, change the type of plants that grow, and make homes for invertebrates and reptiles, many of which are endangered. Their presence in abundance is an indicator of a healthy and natural island ecosystem.

Jo and Rua found 51 burrows in the areas they surveyed around the islands. Six of the burrows belonged to kororā/little blue penguins, but most belonged to ōi/grey-faced petrels. Camera footage (view here) showed that many of the burrows had chicks inside; a sign that the birds are recolonising and doing well in a pest-free habitat.

The ōi/grey-faced petrel is an-all dark oceanic seabird with a short but powerful hooked beak. At sea, they are fast and graceful with a high soaring, powerful flight on long narrow wings. Ōi breed around northern New Zealand on pest-free islands as well as on a few pest-managed mainland headlands. The birds begin breeding in the middle of winter, and nest at the end of a long burrow dug into soil or amongst vegetation. Breeding occurs annually, with very few pairs skipping a breeding season. In August and September, after around 55 days of incubation, the eggs hatch. The parents share both the incubation and care of the chick until it leaves the nest at around 118 days old, and is then fully independent of its parents.

The fact that ōi have started to recolonise Ipipiri is fantastic. Ōi are usually the first of the burrowing seabirds to return once pest mammals are removed. As the recolonisation of burrow-nesting seabird species is critical to the ongoing ecological restoration of the islands of Ipipiri, we plan to use the information gained from the survey to look at how these species could be encouraged to return and once again nest on Ipipiri.

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