Warming seas. Invasive seaweed. Overfishing. The threats facing our coastlines seem insurmountable. But thriving populations of seabirds reappearing on Hauturu may provide reason to hope, says Hauturu Supporters Trust Trustee Chris Gaskin. 

Today Cook’s Petrels are prolific and noisy on Te Hauturu-o-Toi Little Barrier Island.

Their population is in the many hundreds of thousands and they call the island home from September through to May, before they migrate to the Northern Hemisphere.

“They dominate the soundscape now,” says Chris Gaskin, explaining that the vulnerable birds have only been able to return to the island in large numbers  since the eradication of cats and Kiore (rats) in the last two decades.

Cooks Petrel (c) Edin Whitehead

The birds mostly live at sea but return to the shore at night to nurture their nests and raise their hatchlings. And this is when they are vulnerable.

They aren’t the only species whose  numbers are increasing on the island. The New Zealand Storm Petrel, a tiny 35g bird thought extinct until 2003, are reappearing, as are Grey-faced petrels, Fluttering Shearwaters and Diving Petrels.

When these species, which feed a long way offshore where there is still ample prey for the taking, once provided[CG1]  the forests of phosphorus and other nutrients, explains Chris. With their loss, the forest has been deprived.

“There is a cycling of what seabirds bring to where they breed, if they are in big numbers. They bring massive amounts of marine nutrients by their presence.”

He explains this can be through their droppings, and also when they die, their body and feathers accumulate in the ground to enrich the soil. He says this increased diversity benefits invertebrates, reptiles and even terrestrial birds. 

The benefit goes further: in heavy rain, some of those nutrients are washed into the sea, enriching the near shore environments.

“Islands which have never had predators like the Poor Knights Islands have a rich near-shore environment. Islands where predators have been eradicated are showing improvements in near shore environments. In those with no seabirds, the near shore environment is depleted.”

Chris hints that scientists are investigating whether treatments for Kauri Dieback might be developed by thinking about the suite of nutrients that seabirds bring to forest areas. That enrichment is something our mainland forests have lost, with the loss of seabirds breeding throughout most of Aotearoa.

Can safe seabird habitats be found on the mainland? “There are very few areas on the mainland free of predators. We are working with a number of places aiming to get seabirds back, like Tawharanui. That requires predator control to keep the numbers down,” says Chris.

There is a great deal of research left to do, but the work on Hauturu, and in sanctuaries like Tawharanui, and other sites in the north, we can highlight the importance of the nutrient cycling between seabirds, land and sea. . Initially symbolically, but the potential is exciting,” says Chris.

The Seabird Trust has published a guide to seabird restoration titled ‘Restoring Resilience’ about the important role that seabirds have as ‘ecosystem engineers’ and how communities can work to restore populations. The online copy is available here and a printed copy is available for $35. 

 

 

 

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