The Balearic shearwater (Puffinus mauretanicus) is the only endemic seabird in Spain. Until recently it was considered a subspecies of the much more widespread Mediterranean shearwater. It is characterized by having a medium-sized, brown body that changes to cream in the belly area and on the inside of its wings. Specimens with bellies of whiter or grayer tones than the normal pattern have also been observed, but no appreciable differences have been found between sexes or ages.

This endemic species it only breeds in the Balearic Islands, but on its journeys it can reach the Atlantic and the Cantabrian Sea. During its breeding period it can be seen in the waters of the western Mediterranean and the eastern Atlantic, so it is possible to see it during its wintering in French, English waters and even near the North Sea. It can also winter in waters of northwest Africa.  

The shearwater’s breeding season runs from February to June and occurs in the Balearic archipelago, especially on the island of Formentera. This seabird feeds in groups and consumes both small fish and squid that it catches by diving in the water. During the breeding and moulting periods, it feeds on fish discards, while during wintering it consumes only live prey.   
 
Currently, the Balearic shearwater is a species of great importance for biodiversity as it is considered an indicator of the environmental health of the Mediterranean Sea. Although it is also a very endangered species, with a population of around 3,000 breeding pairs. As it is a long-lived species with a low number of chicks per year, it is very sensitive to mortality caused by unnatural causes.
 
Another cause related to the decline of the species is connected to fishing activity. On the one hand, for carrying out longline fishing and for the overcapture of some species on which these birds feed. And on the other hand, due to biological stoppages in fishing activity during the breeding period, which can cause a drop in the productivity of the colonies due to the absence of fishing discards.  
 
Because of these dangers, the Balearic shearwater is included in the Red Book of Birds of Spain (2004) as “critically endangered” and appears as “endangered” in the National Catalogue of Threatened Species. For this reason, with the aim of cooperating in mitigating the decline of the species, the Biodiversity Foundation of the Ministry of Agriculture, Food and the Environment, with the support of the University of Valencia and Barcelona, carry out different projects that are responsible for measuring mortality rates caused by fishing gear and modifying these procedures to help in the recovery of the species.

Likewise, with the basis of the LIFE IBA Marinas project developed by SEO/Birdlife within the framework of the LIFE INDEMARES project, coordinated by the Biodiversity Foundation, 39 Bird Protection Areas have been declared that will allow better protection of seabirds and specifically of our threatened Balearic shearwater.