Packing up and heading home

by ZSL on

The bird team have packed up and been collected from Nelson’s Island. As they come to the end of their time in the British Indian Ocean Territory (BIOT), Hannah Wood, Institute of Zoology, blogs on all they’ve achieved during their fieldwork this summer.

We are now in the final couple of days of our two month research trip to study seabirds in BIOT. We are delighted to report that it has been an all-round success! We have now completed the final leg, which was our 12 day stay on Nelson’s Island.

2018 22 July. Nelsons's Island. Pete Carr.jpg
Nelson's Island

Over the period of our stay on Nelson’s we were able to deploy 40 GPS and GLS tags on Red-footed Boobies and got 38 of those back. During this process we applied unique numbered identification British Trust for Ornithology metal rings to all 40 birds, plus 34 of their partners, so that in the future we are able to recognise recaptured individuals. Now we are back on Diego Garcia we have been able to download and visualise the data and it appears that while rearing small chicks, the parents forage within the bounds of the Marine Protected Area. An example of some of our tag data is shown below. By counting all the visible occupied nests, we calculated that, at this time of year, Nelson’s Island supports a population of 279 breeding pairs of Red-footed Boobies, although our evening counts indicate that there may be a roosting population of around 3000 individuals. That’s a lot of birds for an island which is only 0.31 square km!

2018 July. Red footed Booby tracks. Nelsons Island, BIOT.PNG
Red-footed Booby tracks from Nelson's Island

As well as the Red-footed Booby work, we were very excited to ring and tag Brown Boobies in the Chagos Archipelago for the first time ever. There is a small breeding colony of this larger, heavier species of booby on Nelson’s Island and we were able to deploy 6 GPS-GLS combinations. The Brown Boobies are ground-nesting birds, so this was a new challenge for us, but with a combination of old and new (sometimes nocturnal) techniques, we were able to retrieve 100% of the tags. Having now downloaded the data we can already see that Brown Boobies conduct much shorter foraging trips than Red-footed Boobies. It will be very interesting to examine this data further when we return to the UK.

July 2018. Brown Booby tracks. Nelsons Island, BIOT.PNG
Brown Booby tracks from Nelson's Island

In addition to our work on the Booby species, we discovered that there is a Territory significant colony of Wedge-tailed Shearwaters on Nelson’s Island. We began trialling the use of audio recorders to document the presence of these birds, something which we would like to develop in the future in order to learn more about the size and extent of this population. Towards the end of our stay we also conducted a census of Lesser Noddies breeding in the coconuts. Within the main coconut grove we estimated that there are around 6300 nesting pairs, with a total of 6500 across the whole island.

On the 19th we finally took down our temporary home and were recovered by the crew of the BIOT Patrol Vessel and British Forces BIOT who helped us to transfer all our kit from base camp, onto the ship and back to Diego Garcia. Hopefully we will return this time next year to check up on our new study populations.

2018 22 July. Recovery from Nelson's Island with the BPV in the background. Nelsons Island, BIOT. Pete Carr.jpg
Recovery team collecting Pete, Malc and Hannah from Nelson's Island

We would especially like to thank the large number of people who have supported our research and made this work possible, in particular; BIOTA, British Forces Diego Garcia, the crew and SFPO of the BIOT Patrol Vessel.

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

For more updates from this and future expeditions, follow us on Twitter @BIOTscience.

Previous blogs from this expedition can be found here:

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