Gannet study at Farewell Spit reveals surprising feeding patterns

The gannet colony at farewell spit is an internationally renowned bird sanctuary.
Gabriel Machovsky-Capuska

The gannet colony at farewell spit is an internationally renowned bird sanctuary.

A "groundbreaking" study on Farewell Spit gannets has changed the way scientists believe some animals feed.

The research was led by nutritional ecologist Gabriel Machovsky-Capuska in collaboration with the Department of Conservation and the Nelson Ornithological Society.

They studied the spit's internationally renowned bird sanctuary for four years.

Farewell Spit in Golden Bay is a particularly good example of how sediment transported along the coast can build a beach.
Sarah Dwyer

Farewell Spit in Golden Bay is a particularly good example of how sediment transported along the coast can build a beach.

It revealed the gannets had a sophisticated foraging strategy for targeting certain foods that contained the right balance of nutrients they needed.

He said gannet parents searched for the right prey to bring certain nutrients to their chicks to provide an overall balanced diet.

"As predators, this means they combine individual knowledge of the environment to achieve the food they need to be successful and survive," Machovsky-Capuska said.

The study turns previous research on its head as scientists previously believed gannets fitted into the "optimal foraging theory."

That theory states that animals search for food based on their energy content and to minimise the time spent foraging.

"Imagine that you go to the supermarket and select foods for their nutrients rather than their calories," he said.

The study shows the "sex specific" foraging strategies of gannets is based on obtaining the right nutrients, as opposed to energy use.

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Machovsky-Capuska, a lecturer and research fellow from the University of Sydney, said this had not been seen or studied in any wild predator before.

It had been only observed in laboratory studies with minks, wolf-spiders and beetles.

Gannets are highly successful predators that consume mainly fish and squid.

"We can basically learn a lot of what they do and how they do.

"We can learn about the nutritional value of the food they consumed, obtaining samples from them and we also monitor the environment in which they forage and live and by the way we also live."

Department of Conservation ranger Mike Ogle said the study would give a much better understanding of the whole ecosystem.

"Without studies like this we would be working blind.

"The knowledge helps us to better understand if something goes wrong and why."

Machovsky-Capuska said there were other marine mammal predators, predatory fish and seabirds like that also lived in these environments and consumed similar prey to gannets.

"However, some predators are either endangered or we have small glimpses of their lives that make it extremely difficult for us to fully understand what they eat and how they adapt to environmental changes.

"With this information and our GPS tracking data we can establish how healthy are these environments, how nutrients fluctuate in them and also the quality of food and prey that is available to all these animals in the area."

Ornithologist Rob Schucker said the discovery was "groundbreaking."

"Because we're gaining these longer summers with the weather patterns like el nino, to learn about how these birds are adapting or not adapting is a very interesting component."

He said scientists were still unsure whether gannets had always been selective with food, or it was a result of environmental changes.

Gannets were very adaptable, he said.

"Because of that they can become marine indicators for what's going on in the environment."

Machovky-Capuska said lack of funding has meant he can not continue with the research.  

"In spite of the importance of the project there is not much funding available to continue this type of research.

"Unfortunately, I don't foresee the possibility to continue my work on the Spit, except for if a PhD student to continue with the research and we find some money to continue the project."

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