How tagged petrels survive with geolocators


Researchers have analysed a wealth of data on Trindade Petrels to ascertain whether or not geolocator devices affect their survival.

Tracking devices such as geolocators are now a firmly established part of the conservation toolkit, providing a wealth of information on the movements of individual birds and enhancing understanding of populations as a whole.

Trindade Petrel breeds on the Brazillian island of Ilha da Trindade and on Round Island off the coast of Mauritius (Guillermo Rodriguez Lazaro).

However, some studies have found that, in a small number of cases, these devices could have a negative impact on the survival or breeding success of tagged individuals in some species. Two out of 14 studies found that leg-mounted tags had a negative impact on return rates.

Malcolm Nicoll, of the Zoological Society of London (ZSL), and colleagues combined data from a long-term mark and recapture dataset for Trindade Petrel with information from a geolocator study on the species to assess whether the devices compromised the birds' chances of survival.

In the geolocator study, almost 400 of the petrels on Round Island, in the western Indian Ocean, were fitted with a geolocator on their left tarsus between 2009 and 2012. The whole population there has been studied since 1993, allowing the survival of birds with geolocators to be compared with the rest of the population.

The team found no difference between the survival probability of the birds with geolocators and the rest of the population, either during tracking or in the long-term, meaning the devices have no impact on the Pterodroma petrels.

The researchers suggest the lack of any effect is likely due to the small size of the devices used in comparison to the mass of the petrels, weighing in at less than 1% of their body mass. Devices weighing more than 3% of the bearer's body mass are advised against.

The findings will inform future tracking studies of seabird species, providing insights that can inform conservation strategies and research into threatened species.



Nicoll, M A, Cole, N C, Horswill, C, Jones, C G, Ratcliffe, N, Ruhomaun, K, Tatayah, V, & Norris, K. 2022. No detectable effect of geolocator deployment on the short- or long-term apparent survival of a tropical seabird. IBIS. DOI: https://doi.org/10.1111/ibi.13094