Researchers investigate impact of light pollution at sea on migratory birds

4:49 pm on 8 October 2022

By Pokere Paewai

A Kuaka/Whenua Hou Diving Petrel being checked on Whenua Hou/Codfish Island.

A Kuaka / Whenua Hou Diving Petrel being checked on Whenua Hou / Codfish Island. Photo: Thomas Burns

Migratory seabirds are being affected by light pollution even in the dead of night.

Seabirds like Tītī / muttonbirds face many threats as they make their marathon journeys from the northern hemisphere to Aotearoa.

New research is shedding light on one of the less understood threats, light pollution at sea.

Vessels such as fishing boats, container ships, and cruise ships may all have bright outside lighting that attracts and disorients birds, leading to collisions with ships and subsequent drownings.

Department of Conservation technical advisor Johannes Fischer is currently on Whenua Hou / Codfish Island working with the kuaka or Whenua Hou diving petrel.

"The vastness of the open ocean means that it's very difficult to understand this threat at sea," he said.

"Most of our knowledge comes from terrestrial studies."

Vessels such as fishing boats may have bright lights that attract and disorient birds which can lead them to collide with the vessel and drown.

Vessels may have bright lights that attract and disorient birds which can lead them to collide with the vessel and drown. Photo: Johannes Fischer

To understand light pollution impacts at sea better, researchers at DOC recently attached light-sensitive tracking tags to 179 seabirds across seven different species.

These tags record light exposure events and exactly where they occur.

"We were seeing these light 'events' during the dead of night," DOC principal science advisor Graeme Taylor said.

"At first, we thought they might be lighthouses, but this new research shows these events happening out over the deep ocean where there isn't any land. We've concluded the light must be coming from ships."

The good news is that some of the more endangered seabirds, such as the Chatham Island tāiko, kuaka / Whenua Hou diving petrel, and ranguru / Chatham petrel, seem to encounter relatively little light pollution out at sea.

However, more than a third of tītī Wainui / fairy prions, toanui/flesh-footed shearwaters, and tītī / sooty shearwaters encountered light pollution throughout the Pacific, particularly between Japan and Hawaii, Alaska, and southeast of Aotearoa.

Johannes Fischer said there were steps that could be taken to reduce the harm to seabirds, starting with being aware that some seabirds were vulnerable to light.

Raising awareness among vessel owners would be an important first step, he said.

The next step would be to identify which lights were necessary, and simply turn off those which were not.

"Minimizing light use around seabird colonies, shielding lights, and changing bulbs are some of the many actions that can reduce vessel strikes," Fischer said.

Seabirds are most attracted to blue, violet, and ultra-violet light, so bulbs which filter out these wavelengths also help.

For Ngāi Tahu the tītī is a taonga species and an important part of their mahinga kai around Rakiura Stewart Island.

Fischer works closely with Ngāi Tahu on Whenua Hou.

He said that they shared his concerns around light pollution and support the messaging around minimizing light use.

Get the RNZ app

for ad-free news and current affairs