Recent and exceptional irruption of the Razorbill Alca torda (Linnaeus, 1758) on the Algerian coastline

Abstract

The Algerian coastline, known for its diverse array of fauna primarily dependent on marine ecosystems, has recently experienced notable changes in its community, perhaps due to the severe weather conditions in the North Atlantic. To explore this phenomenon, we conducted an extensive survey of the entire Algerian coast, specifically focusing on fishing ports and beaches, during November and December of 2022. Our objective was to investigate the remarkable and recent irruption of the razorbill Alca torda, which typically spends the winter in the open sea. Throughout our study, we documented a total of 32 sightings of razorbill individuals, including both live specimens observed within harbors (as depicted in Fig. 2 & 3) and deceased individuals washed up on the beaches.

First data on the diet of Razorbill Alca torda wintering in the Mediterranean Sea: insights from social media

“…Displacements occurring at more southern latitudes are also documented, with individuals redistributing across the Atlantic coasts of France and Portugal (e.g., Teixeira, 1986;Pasquet, 1988), extending as far south as the Canary Islands and entering the western Mediterranean in small numbers (Carboneras, 1988). Occasionally, irruption events can occur, with unusually large numbers of individuals entering the Mediterranean Sea and dispersing in countries such as Spain and France, but also Italy, Algeria, Tunisia, Libya, Malta and Greece, as recently documented by several authors (De La Cruz et al, 2022;Balestrieri et al, 2023;Boutabia et al, 2023;Ouni et al, 2023). At a global level, the population size is estimated to be around 700,000 pairs, with most (80%) concentrated in Iceland and the British Isles (Harrison et al, 2021).…”

“…Most of the photographs and videos of Razorbills chasing prey and feeding at sea were made close to the coast or even within ports. This may reflect the fact that photographers and amateurs were concentrated along the coasts as opposed to at sea (Balestrieri et al, 2023), but it may also be due to shallower waters and abundance of small fry that Razorbills could easily prey on, as discussed by Boutabia et al (2023). At the same time, this can also mean that observed individuals were those most easily approachable by photographers, thus possibly representing the weakest individuals within the wintering population.…”

“…Studying seabirds' diet in winter is often complicated by the fact that the individuals stay offshore, thus being difficult to observe. In the case of the 2022/2023 irruption event, many individuals remained close to shore for months at a time and allowed birdwatchers, photographers and other citizen scientists to take photographs and collect data on feeding habits and prey (Balestrieri et al, 2023;Boutabia et al, 2023). Non-invasive methods for data collection such as digital photography and/or citizen science data have been already used as an accurate and efficient method for dietary studies in seabirds (e.g., Ward et al, 2015;Forys & Hevesh, 2017;Gaglio et al, 2017;Viola et al, 2022).…”