Return to Danger Island

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Blog by Hannah Wood, Institute of Zoology, ZSL

Hello again from the British Indian Ocean Territory (BIOT), a chain of coral islands in the middle of the Indian Ocean.

The Seabird Team from ZSL have arrived on Diego Garcia and are preparing for our second trip to Danger Island. The purpose of our expedition is to investigate how BIOT’s breeding seabirds use the Marine Protected Area which encompasses the archipelago. We stayed on Danger Island for the first time in January 2019, and successfully GPS tracked both red-footed and brown boobies breeding on the island. BIOT has two monsoon periods with different prevailing wind conditions, one at the beginning of the year and another around now in July. Boobies breed throughout the year, so we conduct research expeditions during both monsoon seasons in order to capture any changes in the birds’ foraging behaviour caused by the varying conditions.

Photo looking up the beach, with lush vegetation on one side, the ocean on the other and many birds in the air

Danger Island is in the west of BIOT and is an overnight sail from our current location on Diego Garcia in the south. It took us two days to get from London to Diego Garcia where we have been packing our expedition barrels with equipment and food, and programming and preparing our bird tracking tags. Danger Island is uninhabited, with no fresh water or electricity and is 2km long and no more than 400m wide. This means that we need to take everything we require to survive for around two weeks. We have been keeping an eye on the weather and sea conditions and are hoping for a calm day next week when we can land on the island and set up camp.

Photo at night from the shore looking out to sea with the moon reflecting on the waves

Our stay on Danger Island will last around 11 days and we will try to deploy around 45 GPS trackers on red-footed boobies and 15 on the less numerous brown boobies. We will also be deploying activity loggers which indicate when the birds are on or in the water. During our visit we will have the chance to download images from time lapse cameras which we set up in January. If they have survived for the past 5 months, then we will replace the batteries and SD cards and leave them to record the presence of breeding boobies for the rest of the year. In this way we hope to understand more about the breeding behaviour of the birds when we are not on the island.

Photo of a person on a beach, surrounded by plastic litter and debris

This season we will be joined by two turtle researchers, Nicole Esteban and Jacques-Olivier Laloë, who hope to deploy tracking devices on juvenile and adult female green turtles. At this time of year adult females should be making their way up the beaches to dig pits in the sand and lay their eggs. The Turtle Team also plan to take sand cores which are samples of the different layers of substrate that make up the beach. These samples will be analysed for their plastic content, which can affect moisture levels in the sand important for the development of turtle eggs in the nest. Marine plastic is a huge issue across the globe, and despite the remote location of BIOT, we see marine litter on every island we visit. Over the weekend Nicole and Jacques have been leading a team of volunteers gathering marine litter from the Egmont Islands, which are suitable nesting locations for turtles but have a build-up of litter carried from across the ocean. ZSL is working not only to collect and study marine litter, but also to encourage individuals to avoid single use plastic and to choose more environmentally friendly and sustainable options.

When Nicole and Jacques return from the Egmont Islands we will all head to Danger Island together for our joint research expedition, and hopefully find many breeding birds and turtles ready to be tracked!

This research is kindly funded by the Bertarelli Foundation as part of the Bertarelli Programme in Marine Science.

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