March 29 marks one year since BioSciCat technicians cited and photographed, for the first time in Catalonia, a specimen of Wilson's Storm-petrel Oceanites oceanicus. This observation was made in the BioSciCat’s framework of seabirds monitoring in the Golf de Sant Jordi.
Specimen observed on March 29, 2021, at l'Ametlla de Mar. First sighting in Catalonia.
Wilson's Storm-petrel is a bird that breeds in the southern hemisphere, on sub-Antarctic and Antarctic islands. Once the breeding period is over, some specimens make an epic migration that takes them to the northern hemisphere, facing the coast of the American continent, to return to the southern hemisphere through the western Atlantic Ocean. At this time, specimens are detected in the open sea, in waters of the western European and African continents. This species has totally pelagic habits and its observation from land is exceptional.
The presence of Wilson's Storm-petrel in the Mediterranean is accidental, and documented observations are very rare. This is a species hard to detect and identify which, consequently, makes difficult to obtain data.
This first citation in Catalonia was made around the bluefin tuna (Thunnus thynnus) fattening facilities, a place where studies, carried out by BioSciCat, also have cited concentrations of European storm-petrel Hydrobates pelagicus, never before described in Catalonia which, in many cases, exceed one hundred individuals. This specimen was detected in the core of a concentration of 120 European Storm-petrels. Another exceptional fact is the date, the end of March, since the earliest observations in European waters occur in May, and especially from July to September. Undoubtedly, this observation was one of the most unexpected events, ornithologically speaking, in Catalonia during 2021.
Surprisingly, on September 12, 2021, we documented the presence of a second specimen, also in l'Ametlla de Mar. The fact that, in the same year, and as a result of the monitoring carried out by BioSciCat, a couple of specimens of Wilson's Storm-petrel have been documented in the Mediterranean, suggests that the presence of this species is perhaps not so accidental, and that it may have previously gone unnoticed, because of its pelagic habits and the difficulty to identify it. Among vertebrates, the pelagic fauna is certainly the least known by the scientific community.
Specimen observed on September 12, 2021, at l'Ametlla de Mar.
Second sighting in Catalonia.
Therefore, more studies are needed to understand aspects such as phenology or feeding and distribution areas of many pelagic birds. These data are key for the conservation strategies of Procellariiformes, one of the most endangered groups of birds.