The fauna of the Audomarois marsh

Birds, insects, fish, bats, reptiles & amphibians – the animals of the Saint-Omer marsh

Discovering the animals of the marsh

The Audomarois marsh is a true haven of biodiversity, where nature unfolds in a mosaic of preserved habitats. This wetland, characterized by its expanses of water and marshy areas, is home to an exceptionally rich fauna.

Here, birds, whether migratory or resident, offer a daily spectacle of colors and songs, while fish, evolving in symbiosis with their aquatic environment, bear witness to the subtle balance of ecosystems. The presence of rodents and other mammals contributes to the dynamics of the marsh, but are sometimes also invasive… Insects, tireless actors of pollination, as well as nocturnal bats, essential for controlling insect populations, add a fascinating dimension to this biodiversity. Finally, amphibians and reptiles, sensitive to environmental variations, embody the fragility and resilience of this unique natural environment.

This lively and contrasting panorama offers nature lovers an invitation to discovery and contemplation.

The birds of the marsh

In terms of bird life, there are between 220 and 240 species of birds in the Audomarois marsh, as many as in the Marquenterre ornithological park. These wetlands provide an ideal habitat for a multitude of migratory and resident species. Birds of prey, wading birds, ducks and many other birds meet in a balanced and dynamic ecosystem. The diversity of habitats – ponds, reeds and flooded areas – allows these species to reproduce, feed and rest in a preserved natural environment.

Many species reside there year-round, in a sedentary manner. Others only come to visit us in spring and summer. The Romelaere pond, in particular, is ideal for observing colonies.

Among the fauna of the Audomarois marsh, you are likely to quite easily encounter the mallard duck, the coot, the moorhen, the great crested or little grebe, the mute swan, the grey heron, the kingfisher, the lapwing... And many other species!

Discover our special article on the marsh birds.

Aquatic fauna: fish

In the Audomarois marsh, the fish diversity is demonstrated by 26 species of fish that populate its waters. Among them, we first distinguish the carnivores, such as pike, pikeperch and perch, which reign supreme in the depths, as well as the eel, an endangered species requiring special attention. Burrowing fish, such as carp, bream and tench, play an essential role in aerating the bottom and promoting sediment dynamics. Finally, forage fish, like roach, are a vital component of the food chain, serving as food for many predators. This complex balance is evidence of a rich and fragile ecosystem, where each species contributes to the health of the environment. The presence of these 26 species illustrates the marsh's ability to support truly exceptional aquatic biodiversity and makes this site a privileged place for research and observation.

Find our article on the fish fauna of the Audomarois marsh as well as our article on the fishing.

The insects

The Audomarois marsh is a true sanctuary for insects, offering a remarkable diversity that arouses the curiosity of neophytes. There are 86 species of spiders and harvestmen, such as the common tegenaria or small species of reaper, which silently patrol the wetlands. Among the odonates, 18 species of dragonflies, or 21% of French species, evolve gracefully, such as the checkered dragonfly or the marsh auxiliary. The marsh is also home to 98 species of beetles, among which the ground beetle and the scarab attract attention with their robustness. In the group of orthoptera, eight species, such as the green grasshopper or the cricket, enliven the meadows. There are also 90 species of Lepidoptera, including the swallowtail butterfly and various noctuids, as well as 23 species of Homoptera, such as the whitefly and certain aphids, completing this exceptional insectivorous panorama.

Bats

The Audomarois marsh is a real refuge for bats, home to 13 species of bats that reside there or come to feed there. Among them, the Marsh Bat (or Marsh Bat) stands out as the rarest species in France, offering a fascinating natural spectacle, especially during the breeding season when its behavior becomes particularly remarkable. This humid and preserved environment, rich in insects, provides them with an abundant source of food that is essential for their survival. Bats, true regulators of insect populations, thus play a key role in the ecological balance of the marsh. Their discreet but essential presence also contributes to pollination and seed dispersal, strengthening local biodiversity.

Mammals of the Audomarois marsh

The Audomarois marsh offers an exceptional natural habitat for a rich fauna of mammals. Among them, we can observe the discreet weasel and, more rarely, the European badger, real actors of biodiversity. The territory is also home to many rodents such as the vole, the wood mouse, the garden dormouse and the house mouse, essential to the ecological network. There are also emblematic species such as the roe deer, the wild boar, the European hare, the wild rabbit and the red fox, guaranteeing the presence of large mammals. The presence of forest environments in the surroundings contributes to this.

Stone martens, martens, European hedgehogs, stoats and musardins also roam the gardens, fields and undergrowth. The otter, an aquatic species, bears witness to the quality of the water, even if it rarely shows itself. The brown rat and the harvest mouse punctuate the landscape. The European mole completes this diverse panorama, thus offering a remarkable ecological balance. Finally, we find an invasive species: the muskrat or myocastor. More rarely, its big brother, the coypu, can make an appearance there.

Amphibians and reptiles

The Audomarois marsh, with its ditches, canals and ponds bordered by a vast forest, offers a true haven of biodiversity for reptiles and amphibians. In this harmonious landscape, several species coexist, illustrating the richness of local ecosystems. In particular, we find the grass snake (Natrix natrix), whose elegance blends with the peaceful waters, as well as the midwife toad and the common toad, emblems of the amphibian. The Lessona frog, the common frog and the green frog populate the wetlands, bringing color and vitality to the aquatic environments. Among the reptiles, the viviparous lizard and the slow worm bring a touch of dynamism, while the Florida turtle, an exotic species, adapts to local conditions. The latter, fortunately, is becoming increasingly rare. The newts, whether alpine, crested, webbed or spotted, as well as the spotted salamander, perfectly illustrate the diversity and fragility of this unique environment, a true natural setting.

Mollusks

The Audomarois marsh contains a remarkable diversity of molluscs, testifying to the richness of its aquatic and terrestrial ecosystems. Among them, snails and slugs, true actors of decomposition, transform organic matter into essential nutrients. These gastropods, sensitive to environmental variations, illustrate the fragile balance of this environment. The presence of anodonte, a freshwater mussel, enriches biodiversity by filtering the water and improving its quality. Together, these molluscs actively participate in the natural dynamics of the marsh, making this place a true laboratory of life where each species plays a vital role.

Invasive species

The Audomarois marsh, rich in biodiversity, is facing the invasion of certain species that disrupt the natural balance. The muskrat, accidentally introduced, has established itself permanently and is modifying the structure of the banks through its digging work, thus affecting the riverside vegetation. The Florida turtle also represents a threat. As an adult, it can reach 30 centimeters and is distinguished by its red spots around its eyes. Hibernating from November to March, this exotic species is a formidable predator, feeding on amphibians and local fish, and competes with native turtles for access to resources. The American crayfish completes this worrying picture by modifying the dynamics of aquatic ecosystems through its rapid reproduction and predation on native invertebrates. Together, these invasive species contribute to unbalancing natural interactions and pose a major challenge for the conservation of the Audomarois marsh. Their urgent management remains absolutely essential to preserve the ecosystem.

Find in this pdf the complete list of the fauna of the Audomarois marsh (complete inventory)

The fauna of the Audomarois marsh

Birds, insects, fish, bats, reptiles & amphibians – the animals of the Saint-Omer marsh