Keeping an eye on Balearic Shearwater
By Pep Arcos, David García, Daniel Oro, Meritxell Genovart & Maite Louzao, Sat, 04/07/2015 – 06:46
It’s been over a decade that Balearic Shearwater has held the dangerous title ‘Critically Endangered’, which puts it at the very top of the European Red List of Birds. To make sure it doesn’t disappear before our very eyes requires some very careful monitoring at sea, where it spends most of its life, and also on land where it breeds. But so far we haven’t been doing enough to ensure the conservation of this species and if we wait any longer, we might notice too late that it’s gone forever.
Balearic Shearwater may not be the most colourful bird, it’s rather brownish and could be mistaken for a gull by an untrained eye, but it’s special. Only found as a breeder in the western Mediterranean’s Balearic Islands where it nests in caves, crevices and under rock boulders in inaccessible sea cliffs and small islets. We think there are just a little over 3,000 breeding pairs, and maybe a global population of about 25,000 individuals. It’s long lived, most likely some birds live over 30 years though we have no sound data on this, it begins mating at 3 years of age, and lays a single egg per year. Losing adult birds is therefore of serious concern, as they are not quickly or easily replaced. Unfortunately, the population has been steadily declining as a consequence of several threats, particularly fisheries bycatch at sea and predation by invasive species on land. This trend is alarming and scientists say it could become extinct in slightly over half a century.
Over the last decade, we’ve learned quite a lot about the Balearic Shearwater’s ecology at sea. Nearly all of its breeding colonies, plus the main Spanish marine hotspots, which were identified by SEO/BirdLife’s marine team have now been designated Special Protection Areas(SPAs) under the Birds and Habitats Directives. Rat eradication has been addressed in some colonies. This is all good but we need to do more to safeguard the species. For one, management plans for these SPAs haven’t been implemented, and wider conservation action at sea is also missing. Furthermore, despite being one of the priorities highlighted in the Species Action Plan, we still don’t have a proper breeding monitoring programme in place. Without monitoring, we cannot understand the dynamics of the population, and so updating its conservation status and assessing the suitability of conservation actions (e.g., reducing bycatch rates) are impossible or at least unreliable.
Two recent initiatives are trying to address the gap created by the lack of monitoring programmes, one in W Mallorca (where colony monitoring had already been conducted in the late 1990s and early 2000s) and another in the southernmost of the Balearic Islands, Ibiza and Formentera. Here we describe the latter, where SEO/BirdLife is directly involved, working closely with researchers from AZTI-Tecnalia, IRBI and other institutions, with support from the Natural Reserves of West Ibiza Islets. Most of the work is in Sa Conillera islet, off west Ibiza, and it began in 2011, within the framework of Interreg Project FAME, in close collaboration with LPO and CEBC-CNRS. Geolocators have been placed on a number of birds so we can better understand their movements in the Atlantic outside the breeding period. They’ve also been GPS-tracked during the breeding period, which has allowed us to monitor their habits during breeding as well.
On top of monitoring movement, about 120 nests are checked at least twice each year in Sa Conillera and the islets of Es Bosc and Espartar, which are close by. First, during the incubation period, nest occupancy and identification (and ringing if required) of adults is done at each nest. Late in the season, nests are visited again to ring and find out which chicks have fledged. Surveys of other colonies are being conducted in parallel in other islets of Ibiza and Formentera, with particular attention to the Natural Park of Ses Salines. These efforts were also supported by another major project, LIFE+ INDEMARES, as well as the Spanish Institute of Oceanography (IEO) and the Ibiza Preservation Fund (IPF).
Monitoring is just one step forward to saving this Mediterranean jewel, the most threatened bird in Europe. But to be sure the species doesn’t vanish forever we must set up monitoring programmes in other Balearic Islands. Also, we can’t forget what happens at sea, because this is where this species spends most of its life. With this in mind, SEO/BirdLife and BirdLife Europe’s new European Seabird Task Force is now working with fishers to find ways to ensure they keep catching fish rather than seabirds.