What happened to the birds in Las Tablas de Daimiel National Park after the water crisis?

Wetlands are ecosystems that, despite providing a wide variety of ecosystem functions, are in serious decline. A clear example is the Las Tablas de Daimiel National Park.

Is the situation of Las Tablas de Daimiel that serious?

The Daimiel Tables have undergone variations in their water regime throughout their history. In recent years, due to the overexploitation of the aquifer that supplies it for the use of human activities, its water regime is in critical condition, reaching only 623 ha in 2024 with the presence of water of the 1800 ha that are floodable.

As a result, the great biodiversity of flora and fauna that houses the National Park is in serious decline. Among the birds present in the wetland, marsh passerines stand out, a group highly specialized in wetlands and coastal areas, and little studied due to their difficult detection and such specific habitat requirements.

Objective of the study of these birds

We set ourselves the objective of knowing the situation of five species of passerines in the face of the water crisis that the wetland is going through by studying their population trends and habitat requirements. Species and their conservation status (IUCN) are:

• Tordal Warbler (Acrocephalus arundinaceus). NT “ALMOST THREATENED”
• Look for the unicolor (Locustella luscinioides). NT “ALMOST THREATENED”
• Moustached (Panurus biarmicus). I SAW “VULNERABLE”
• Royal Carricerin (Acrocephalus melanopogon). I SAW “VULNERABLE”
• Ibero-Eastern Marsh Scriban (Emberiza schoeniclus witherbyi). CR “CRITICALLY ENDANGERED”

What did we discover in Daimiel's Tables?

The results showed that there is a strong relationship between population trends and the wetland's water regime. Thus, a population increase was observed after the favorable period of rains from 2010 to 2016, which allowed optimal flood levels to recover, and a subsequent population decline starting in 2019 due to the current water crisis as a result of illegal extractions from the aquifer 23.

This population decline can be explained because all marsh passerines have as a habitat requirement the presence of open water in the wetland, this is due to the great benefits it provides them with:

• It acts as a food source by increasing the presence of aquatic insects included in the diet.
• It insulates nests, making them inaccessible to predators.
• It allows the growth and maintenance of the marsh vegetation on which marsh passerines depend for their lives.

The hedgehog (Phragmites communis), the farmhouse (Cladium mariscum) or Enea (Typha domingensis) are highly water-dependent plant species that act as a refuge for marsh passerines. Thus, they provide them with protection, material for the construction of the nest, support for perching and food.

Conclusions

The water crisis that Las Tablas de Daimiel National Park is experiencing leads to the absence of water and, as a consequence, the drying up of the vegetation. The loss of the resources provided by vegetation to marsh passerines makes it impossible to maintain their populations in the National Park.

Finally, it should be noted that studies on habitat requirements and population trends are very important for threatened species such as marsh passerines in declining wetlands such as Las Tablas de Daimiel National Park, to effectively target management and conservation efforts.