14 - The Gautegiz Arteaga marshes

We are now looking at the marshes of Gautegiz Arteaga, one of the most valuable places in Urdaibai.

The wetland we see in front of us is made up of two clearly distinct areas. The closest one has an elongated shape and is a fresh water lagoon. Beyond the dike or dividing barrier, there is a salt water lagoon, much larger than the previous one and connected to the tidal flow. Thanks to a floodgate system, this lagoon is never drained completely, and this helps to maintain bird diversity.

The surrounding landscape is also highly valuable. On the bottom-right side of the marsh, we will find very interesting areas of Atlantic countryside dotted with Basque farms, hedges, planted forest crops and Atlantic woods. Oak stands grow on both sides of the wetland, not only increasing the ornithological richness of the area, but also mitigating the impacts caused on birds by human activity. Both copses are managed by the Aranzadi Society of Sciences by a project of land stewardship.

Rising above the fields and farms, on the limestone hills that roll down to the sea, we will find a thick evergreen forest. It is known as the “Cantabrian holm oak wood”. It grows on both sides of the estuary, making up the largest natural forest in the Urdaibai Biosphere Reserve.

Beyond the lagoons, we will see the river’s old meander, through which the tide rises and falls. There is also a vast plain of supra-tidal marshes, that is, an area which only gets flooded during spring tides or periods of heavy rain. At the bottom of this flood plain stands Murueta Shipyard, the place where the tides can be detected more easily.

These marshes are very rich in bird life; in fact, about 200 species can be seen here. Several reasons account for this diversity. On the one hand, these waters hold plenty of available food fish and small invertebrates, and this is exactly what migratory birds need to recover their strength. On the other hand, the water has varying degrees of salinity and depth, and this attracts birds with different habits and characteristics. And finally, birds need tranquility. This wetland managed by Urdaibai Bird Center has become a small paradise safe from human disturbance, and that’s why birds stop here year after year during their migrations.