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The Cory's shearwater (Calonectris diomedea) is a seabird that, like the rest of the species of this group, is specifically tailored to develop its life in the harsh conditions imposed by the marine environment. This high specialization makes them particularly vulnerable to sea degradation. Not surprisingly, seabirds are the most threatened group of birds worldwide, even more so than tropical forest birds.
Besides facing the annoyances and problems inland, such as nesting habitat digression and predation, seabirds will have to survive the changes in sea conditions due to the climate change and, above all, the reduced food availability that it will entail. The Cory's shearwater may be particularly sensitive to environmental changes and, therefore, a good indicator of the ecosystem health status.
Cory's shearwaters spend most of their life at sea, where they feed and rest next to their congeneres, forming floating compact groups called rafts. However, when breeding, they go to shore to nest in cliffs, lay their eggs and raise their chicks. Their specialized life cycle and their discreet looks makes them a largely unknown species to most of society. The Cory's Shearwater is classified as vulnerable in Europe and could become and endangered specie in the Mediterranean sea.
Nowadays, fewer than 10,000 of Cory's shearwaters are estimated to live in the Spanish Mediterranean coast, mostly in the Balearic Islands. To make an estimate of the evolution of their populations and be able to detect a negative change for this species it is necessary to have a good starting census, to know all breeding sites and to keep this information updated.
This basic knowledge is especially difficult to obtain for the Cory's shearwater because it nests in colonies placed in locations with difficult access: cliffs, rocky islets ... An exceptionally difficult place to work can be found on the north coast of Menorca.
The Vell Mari, within the program of Obra Social La Caixa "la Caixa for the sea: the route of the Vell Marí", has dedicated a specific campaign to count Cory's shearwater nesting populations on the north coast of Menorca, where this species has one of the three largest colonies in the Mediterranean sea, next to the islands of Cabrera and Chafarinas. This study was undertaken to update the data from the last census, which was conducted 17 years ago.
The results obtained from the nocturnal census, done through sound monitoring at specific locations pointed out by our experts, have added to the specific census done over the years. In this sense, changes in populations of this endangered species and protected by the EU will hopefully be detected on time to be able to take effective protective measures.
After a first exploration of the walls of the cliffs from the sea, a photographic record and a selection of the sectors best suited to accommodate reproduction nuclei, we proceeded to count the vocalizations of the breeding pairs through consecutive nocturnal sound monitoring. This was done at each chosen location in order to estimate the approximate number of existing partners.
The first results are not optimistic. From the last estimate, it appears that the nesting population has declined significantly in Menorca, probably as a result of the continuous predation of nests from nocturnal birds of prey, gulls and introduced mammals such as rats, cats and goats, and as a result of fishing activities, in addition to the loss and alteration of their habitat.
Location: north coast of Menorca
Completion date: from July 28 to August 3
Administration, scientists and experts:
- Joan Mayol, Chief of the Protection Service of Species. DG of Hunt, Species Protection and Environmental Education of the Government of the Balearic Islands.
- Carles Carboneras, marine ornithologist and researcher. Collaborator of BirdLife International.
- Miguel Rodriguez and Anne McMinn (S.L Skua). Specialists in monitoring seabirds and collaborators of the DGCAPEA.
With the participation of the DG of the Sea of the Ministry of Environment of the Government of the Balearic Islands.
Watch the final report in PDF format:
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Shearwater breeding