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Author: Dries Engelen, Louie Taylor, Martin Austad

UPDATE: The young Audouin’s gull is still around Malta, as it was observed again on 29.12.2021, this time by Denis Cachia.

Juvenile Audouin’s gull, ringed near Lastovo, observed on 29th of December 2021 in Malta (Author: Denis Cachia)

In mid-October we received some great news from BirdLife Malta, one of the partners on the LIFE Artina project, saying that a juvenile Audouin’s gull with Croatian ring was seen in their country. The bird was seen and photographed by Mario V. Gauci on the 15th of October, bearing a yellow colour ring with code P8. The gull was ringed as a chick in the Lastovo Archipelago, Croatia, less than four months prior, as part of the LIFE Artina project.

Juvenile Audouin’s gull, ringed near Lastovo, observed on 15th of October 2021 in Malta (Author: Mario V. Gauci)

Audouin’s gull is a scarce and threatened breeding species of Croatia and because of their limited distribution in the country, they are less known compared to their widely distributed and numerous relative, the Yellow-legged Gull (Larus michahellis). Generally, the Audouin’s gull inhabits the area of the Mediterranean Sea, with its most numerous breeding colonies on the delta of the river Elba in Spain, the Balearic Islands, the Algarve, the Tuscan Archipelago and Sardinia. In the rest of its distributional range the species breeds in smaller numbers.

Audouin’s gull in the Lastovo Archipelago (Author: Biljana Ječmenica)

In the Adriatic Sea they breed in small numbers and their breeding in Croatia was first confirmed in 1996. They breed on islands within the Lastovo and Mljet archipelagos and around the island of Korčula and the peninsula of Pelješac. As they tend to shift the locations of their breeding colonies between years, it is difficult to implement some sort of species protection on them. In the Croatian Red Book of Birds, it is estimated that 60 to 70 pairs breed on our islands. That estimation is based on data collected in the beginning of the century where in 2001, 69 pairs were found, in 2005, 56 to 59 pairs and in 2006, 57 pairs were found. During LIFE Artina, we found 29 to 38 pairs breeding in the Lastovo archipelago over the last 3 years, which comprises nearly all breeding pairs in Croatia. The breeding population of Croatia is endangered (EN according to the International Union for Conservation of Nature, IUCN) because of their small breeding numbers and limited area of distribution. Globally they are vulnerable to extinction (VU according to IUCN) because of the decline of adult individuals, in part due to predation and changes in food supply.

Yellow-legged gull (left) and Audouin’s gull (right) (Author: Biljana Ječmenica)

The Audouin’s gull is closely related to our more common species of gull, the Yellow-legged gull. It can be distinguished from them by their red beak, dark eyes, greyish-green legs and light grey mantle. Compared to the Yellow-legged gull, the Audouin’s gull is a proper seabird. It inhabits coasts, islands and the open sea, and they rarely go deeper into the mainland. After the breeding season, they stay within the Mediterranean Sea (alongside the coasts of Spain and Italy) or they migrate to the coasts of Morocco. The main food source of the Audouin’s gulls are fish, cuttlefish, crustaceans, insects, but they can rarely consume small birds or plant matter like olives and seeds. Unlike other gulls, they rarely feed on human waste. They hunt characteristically by flying low and slow, with rigid wing beats while dangling their feet. When they spot their prey, they nose dive and grab it by immersing only its beak, and occasionally their head. They breed on rocky islands with limited vegetation, similar to the Yellow-legged gull. As Yellow-legged gulls start with breeding earlier than Audouin’s gull and are more aggressive and numerous, they take the more favourable breeding sites. Besides they have also been observed to prey on the fledglings of Audouin’s gulls, further decreasing the breeding success.

As a part of LIFE Artina we are working to better understand the ecology and biology of Audouin’s gull and how to implement protection for them. Aims of the project are to identify Special Protection Areas (SPA) important for threatened seabird species of Croatia, and to understand, evaluate and mitigate the main negative effects on their populations. Therefore, we conducted yearly breeding pair counts in the Lastovo Archipelago, tried to mitigate the negative impact of Yellow-legged gulls, and colour-ringed and tagged a number of individuals in order to understand their movements and behaviour. Colour ringing allows for identifying different individuals throughout the years, which is of great importance for long-lived species. Apart from the Maltese observation of the juvenile Audouin’s gull in October, another great example of this are two Audouin’s gulls which were found nesting in the Lastovo Archipelago in May 2019, and which had been ringed as chick in the Mljet Archipelago more than ten years prior to that!

Colour-ringed adult Adouin’s gull (Author: Luka Jurinović)

Colour-ringing, together with GPS-tagging, helps in understanding several aspects of the ecology of the species, such as where Audouin’s gull ends up breeding, where it forages and where it moves during the year. Better insights in their movements are important for the protection of the species so we can better understand the areas they use and threats they face. Some of the individuals that we tagged in the Lastovo archipelago have migrated to the Atlantic coast of Morocco (around 3 000 kilometres away) and we even got a recovery of a ringed Audouin’s gull from Senegal (over 4 000 kilometres away). These recoveries show that some of our Audouin’s gulls migrate a lot further than we previously thought!

GPS track of an Audouin’s gull tagged in the Lastovo Archipelago, wintering in Mauritania

We hope to discover lots more about these mysterious gulls during the LIFE Artina project and in the future! For now, we wish P8 the best of luck on its autumn migration and hope to see it back around Lastovo as a breeding adult one day!