Dining habits of breeding terns revealed

Dec 20, 2013 by Lizzie Thelwell
Dining habits of breeding terns revealed
Bridled terns have been increasing at a very fast pace on Penguin Island since the 1950s. Credit: A Labbé

Western Australian researchers have used stable isotope ratios from the tail feathers of bridled terns (Onychoprion anaethetus) on Penguin Island to assess how their feeding habits vary during the breeding season.

Increasingly popular with ornithologists, analyses provide information on a bird's food web and feeding level from a single capture.

The Murdoch University study took samples upon arrival, before egg-laying, after egg-laying, after hatching and from fledglings.

"It was a beautiful thing to look at the stable isotope graphs and almost be able to super-impose a map on them. Bridled remind me of small flying computers and data-loggers," says lead researcher Aurélie Labbé.

"Our research highlighted how bridled terns use different feeding grounds while breeding on Penguin Island, while also showing how much they restrict their diet to specific prey items while raising their chicks.

"The birds feed on almost anything they fancy until they have their chicks, and then they become highly selective of what they eat and what they bring to their young."

The starts when the adults arrive on the island from the Indonesian Archipelago during the second half of September. 

During this time, their diet can be very diverse and include small fish, terrestrial insects, crustaceans – including crab larvae – and cephalopods such as small squids.

When egg-laying begins, their diets become restricted to prey found in the waters offshore and adjacent to the island, with crustaceans and black-spotted goatfish representing a significant portion of their diet in the mid to late parts of the breeding season.

"During the breeding season, they become central place foragers as they must return to their nesting sites from feeding ground to incubate and raise their chicks until the fledglings become independent," Ms Labbé says.

She says the information is important for conservation because it provides a better understanding of how this species uses its environment in WA.

"Bridled terns have been increasing at a very fast pace on Penguin Island since the 1950s. This reflects a change in the climatic and oceanic conditions around this WA ecosystem which has been greatly favourable to the species.

"While many studies focus on endangered species and those threatened by the effects of climate change, species that benefit from global warming also deserve our attention.

"They add a new dimension to the equation of ecosystem dynamics, and we need to know more about them."

Explore further: A penguin's tale: Diet linked to breeding failure

More information: Labbé, Aurélie M. T., Dunlop, James N., and Loneragan, Neil R. (2013). "Central place foraging and feather regrowth rate in bridled terns (Onychoprion anaethetus): an insight from stable isotopes." Marine and Freshwater Research 64, 1184–1191. dx.doi.org/10.1071/MF12334

add to favorites email to friend print save as pdf

Related Stories

Spotted: Rare spotted penguin

Jan 31, 2013

(Phys.org)—Little penguins, also known as fairy penguins, usually have a white belly and dark blue back to camouflage them from predatory eagles above and their fish prey below.

Recommended for you

Orchid named after UC Riverside researcher

17 minutes ago

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

2 hours ago

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

2 hours ago

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Tiny power plants hold promise for nuclear energy

Small underground nuclear power plants that could be cheaper to build than their behemoth counterparts may herald the future for an energy industry under intense scrutiny since the Fukushima disaster, the ...

Hand out money with my mobile? I think I'm ready

A service is soon to launch in the UK that will enable us to transfer money to other people using just their name and mobile number. Paym is being hailed as a revolution in banking because you can pay peopl ...

Classifying cognitive styles across disciplines

Educators have tried to boost learning by focusing on differences in learning styles. Management consultants tout the impact that different decision-making styles have on productivity. Various fields have ...