The masked booby faces an increasingly moveable feast as its ocean prey swims randomly from one spot to the next, making it vulnerable to overfishing and habitat destruction, a University of Sydney led project has revealed.
A field-based study of 27 breeding pairs found on average the plunge-diving booby birds were flying 50 kilometres to find adequate fish and squid supplies for their diets. The full results of the project have been published this week in New Zealand Journal of Marine and Freshwater Research
The international research team, which included vet scientists, coastal-marine researchers and electrical and information engineers, camera-tagged and monitored a group of female and male birds for several weeks on Lord Howe Island.
Study leader Dr Gabriel Machovsky-Capuska, a nutritional ecologist from the University of Sydney’s Charles Perkins Centre and Faculty of Veterinary Science, said the team combined bio-logging technology with nutritional analysis to provide first-of-their-kind details on the amount of nutrients consumed by masked boobies after each of their hunting and gathering trips.
“We discovered the increasingly long distances flown by these birds caused them to burn more calories than they were consuming. Additional studies would help us understand whether changes in the nutrient balance will render them unable to make the long journeys.
“It’s as if you’re trying to go shopping for groceries, but the supermarket is on a rail track that continuously moves around the city and is never in the same place,” says Dr Machovsky-Capuska.
An important part of the project was to discover what prey masked boobies actually consumed, such as fish and squid, and their differing nutritional value.
Researchers studying the foraging behaviour of wild animals face the significant challenge of undertaking the lengthy observations needed to correctly to interpret mannerisms and food intake.
Miniature cameras developed by engineering researchers measuring approximately the size of three Tim Tams and weighing only 60 grams were attached to the birds’ tail region allowing the researchers to understand whether boobies forage alone or with other marine animals in the ocean.
Video footage showed boobies diving in the company of sunfish, who prey upon zooplankton, as well as flying fish, one of the boobies preferred prey.
The bio-logging technologies refined by the University’s electrical and information engineers assisted the cross-disciplinary study of the boobies to capture 17 hours of footage at a time.
Dr Peter Jones, research engineer, explains: “Bio-logging is the use of miniaturised animal-attached tags for logging and relaying data about an animal’s movements; behaviour and physiology, in this case the booby birds.
“One challenge we overcame was balancing the need for continuous filming over extended periods versus the addition of on-board sensors attached to the boobies to enhance the information collected.
“We used a combination of technologies including GPS data loggers coupled with miniaturised cameras.
“We also optimised battery selection to meet the power demands of the bio-logger while acknowledging the weight and size constraints imposed by the boobies, and their plunging diving from high altitudes into the water to pursue their prey.”
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