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EZS and the Port of Ibiza

13 November 2022

Ibiza ornithology

Today we would like to introduce you to EZS... EZS is a xatrac; sandwich tern (Thalasseus sandvicensis), and he has two rings on his legs. The one on the right leg is metallic, this type of rings are those of the official organisation that manages the production of rings in the area where it was ringed; and the one on the left leg is made of PVC, with a code designed to be read from a distance. Both rings have a unique code, there are no two alike (if this were the case, scientific ringing would lose part of its usefulness as it could confuse individuals in different parts of the world). Through the code of the PVC ring, which is EZS, we have been able to contact the banding group responsible and learn something of their history.

scientific ringing ibiza

EZS was ringed as an adult in Scotland in 2011 (which implies that he is at least 11 years old), and it seems that he likes to spend the winter in our beloved Pitiusas, specifically in the Port of Eivissa, where he is often seen with other members of his species.

Sandwich Tern Thalasseus sandvicensis Ibiza

Their breeding colony is on the Farne Islands, where this past summer there was an outbreak of avian influenza, which killed more than 3,000 wildlife birds, a disaster that our friend has survived.

bird migration Ibiza and Formentera


If we can find out where it comes from or where it breeds and since when it has been documented, it is, as already indicated above, thanks to the unique code on its remote reading ring, the big PVC one.

Through this code, we have contacted the organisation responsible for its marking, and apart from giving them the sighting report, you also kill the inevitable curiosity to know what its history is and how long it has been around.

For those who want to know how to get in touch with the people in charge of a remote reading ring tagging project, there are several options. On the one hand, the Doñana Biological Station, which can help you to find the project to which the ring is associated, if you send them the code information. Another option is this website, where there is a search engine that allows you to locate the possible projects to which it may belong, based on a previous filtering based on the type of code, ring colour and species. Last but not least, asking in specialised groups on social networks is also very useful.

birds port of ibiza

Text: own elaboration.

Photographs: Borja Pérez.


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Wildlife control in Ibiza