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The sandwich tern in the saltworks of San Pedro del Pinatar ¿”Goodbye forever” or a “see you soon”?

Over the decades, humans have shaped the landscape and the biological interactions between its different elements. Sometimes, changes in habitats and landscapes are associated with a revolution in the faunal communities that can be found there. In this sense, some coastal saltworks, despite their artificial nature and the fact that they were created with the aim of exploiting salt, have seen their extensions naturalised over time, creating habitats that are ideal for a wide range of species.

The San Pedro del Pinatar saltworks, despite historically forming part of the mosaic of wetlands that are distributed around the Mar Menor, continue to be visited by new species of waterbirds, some of which become established as breeders, such as Audouin’s Gull (Larus audouinii), Gull-billed Tern (Gelochelidon nilotica), Sandwich Tern (Thalasseus sandvicensis) and, more recently, Cattle Egret (Bubulcus ibis), Little Egret (Egretta garzetta) and Glossy Ibis (Plegadis falcinellus). The changes are taking place, not only in these saltworks, also in the immense number of landscapes and practices that take place in their surroundings and which have a significant influence on the life and behaviour of these species.

This time we focus on the Sandwich Tern, a species that since its arrival in the saltworks of San Pedro del Pinatar in 2008 has shown marked variations in its breeding population. Undoubtedly, these fluctuations are the result of inter-annual variations in the availability of food or feeding areas, competition for nesting sites, weather conditions during the breeding period, etc. On the other hand, the colonial nature of this species encourages it to function as a metapopulation made up of a group of nearby populations of the same species among which there is a flow of breeding individuals. This fact is one of the main factors that seems to explain the fluctuations observed in its breeding population, these changes being cushioned by the increase or decrease of neighbouring populations located in Almería and the south of the Comunidad Valenciana.

During the breeding period of 2021, the presence of Sandwich Terns in the saltworks of San Pedro del Pinatar was quite scarce, the species seemed to have moved to other areas. Weeks after the LIFE SALINAS Project monitoring team detected this situation, colleagues from Alicante reported for the first time the reproduction of this species in the Torrevieja saltworks (http://ahsa.org.es/avifauna/abandonos-colonias-charranes), located some 25 kilometres away, with a colony of 800 breeding pairs. Unfortunately, a few days later, a succession of torrential rains triggered the abandonment of all the nests. Parallel to the disappearance of this colony in the Alicante wetlands, a small colony of less than 20 Sandwich Tern pairs settled in the saltworks of San Pedro del Pinatar.

Sandwich Tern colony during the nest count carried out by LIFE SALINAS technical staff.
Sandwich Tern colony

Cases like this show that the implementation of management and conservation measures on our habitats and biodiversity is necessary and, in most cases, beyond the limits of protected areas or directly and exclusively on the species under conservation. The continuous degradation of the Mar Menor, changes in fishing activity or in the aquaculture facilities in the area or, in the long term, changes in marine currents associated with global warming, are some of the factors that can motivate and intensify variations in the reproduction areas of this and other species.

To date, the Sandwich Tern is still part of the breeding waterbird community in the salt flats of San Pedro del Pinatar, but… What will happen if the environmental conditions continue to change?

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