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September 2020
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SPEA is an Environmental not-for-profit organization whose mission is to support research and conservation of wild birds and their habitats, by promoting sustainable development for the benefit of future generations.
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Individual seabird tracking

When we track seabirds we use some of the very latest and greatest technology. It is very complicated to understand seabird behaviour in the open ocean, for we are dependent on the information given by different types of small devices attached to the bird itself.

We thought it might be interesting to show here some of these gadgets, the ones currently being used in FAME project, and to explain how they work.


This is the latest tag technology which uses the same satellite technology as in a car sat-nav system to tell us, in high resolution, where the birds have been going. The tag weigh in the region of 16 grams and is attached just to the feathers on the birds back using waterproof tape. This method means that the tag will stay attached for about a week, during which time we will try to re-catch the bird so that we can take the tag off and download its precious data. If we do not manage to re-catch the bird then the tag will fall off so that the bird does not have to carry it for too long.

Releasing a shag@Ellie Owen

TDR trags

TDR stands for Time Depth Recorder. These tags were originally designed for use on fish where they would record the depths that the fish were at by measuring the water pressure very precisely. Now they have been designed for use with seabirds and give us information on what depths the birds are diving to for food. When we use these tags on a bird which is also wearing a GPS tag we get incredible 3-D information on where the bird went and how deep the bird was diving when it got there. This kind of information is exactly what we need for trying to work out which food resources are important to our seabirds and why.

GLS tags

GLS tags are very small and very clever. They measure light levels and the time of sunrise and sunset to work out a location estimated to within about 200km. The benefit of these tags is that because they are so small they can be attached to a small ring to be worn by the bird on the leg for a year or more.  The data is not to the same high-resolution as GPS tags so we cannot use these tags to look at exactly where birds are foraging but instead we use them to tell us about where birds are going over the whole year.

Kittiwake wearing a GLS-tag@Liz Mackley

There are also other kinds of tracking devices, and each has advantages and disadvantages regarding precision, potential amount of data recovered, and device weight. In the last decade, advances in technology have been able to produce more accurate results, and lighter devices that can be used in smaller sized species. The following table will clarify the different types of tracking devices used for seabirds:

Main tracking methods - adaptaded from Ramírez et al, 2008. Important Areas for Seabirds in Portugal.

                                                                 Cory's shearwater@Pedro Geraldes

  • Tracking work underway:

SPEA in collaboration with Dr. Vitor Paiva (IMAR/CMA) deploys GPS-loggers each year on Cory’s shearwaters on Berlenga island, to be recovered in the end of May (pre-breeding period monitoring). In June 10/15 devices will be deployed on Yellow-legged gulls. In September, more Cory’s are marked to track the feeding trips and foraging areas during chick-rearing period. Also during FAME project Madeiran Storm-petrel Oceanodroma castro was tracked with GLS devices.

SEO/BirdLife team has marked 40 Balearic shearwater in Ibiza, also with GLS devices, in collaboration with CEBC-CNRS (collaborating with LPO). This team will also deploy 5 PTTs on the same species, in May/June. SEO will also track Cory's shearwaters with GPS-loggers this summer, at least near Gibraltar (about 20-30 devices) and maybe also Galicia, though the latter site will be difficult as the colonies are considered to be very sensitive to disturbance.

LPO, in colaboration with CEBC-CNRS, has been monitoring the Northern Gannet colony in Sept-îles National Reserve. In 2010, 35 GPS-tags have been deployed to register feeding trips durind nesting period.

RSPB is also performing tracking work in the remote islands of Fair Isle, Orkney and Colonsay. Investigators are using GPS-tags, GLS-tags and TRD-tags to track Fulmars, Shags, Kittiwakes, Guillemots and Razorbills.


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