The Miño river Estuary is the most significant natural area in A Guarda. The mouth of the river forms a delta and is considered one of the most important wetlands on the Iberian Peninsula, with the confluence of both ecosystems, fluvial and maritime.
The variety and number of birds that choose the estuary for wintering are recognised by biologists and ornithologists experts. It has protection as:
- Natura 2000 Network.
- Included since 1965 on the List of International Relevance Wetlands of Europe and North Africa.
- Special Protection Areas for Birds (SPA).
- Special Protection of Natural Values (SPNV).
From the Bird Observatories, a path runs the last kilometres of the river mouth. This path has informative panels giving details about the estuary, the wildlife, the vegetation and environmental elements.