THOUSANDS OF BIRDS CROSS THE SKY
Currently, during the post-nuptial migration, the SEO/BirdLife Ornithological Reserve in O Grove becomes a privileged observatory to witness one of nature's most impressive phenomena: bird migration. This process, essential for the survival of many species, represents one of the most complex and coordinated movements in the animal kingdom.
Avian migration consists of periodic and regulated movements of individuals between breeding areas and wintering grounds, in response to seasonal changes in resource availability, mainly food. These movements, which repeat in biannual cycles, are not primarily motivated by low temperatures, but by their consequences: the search for optimal conditions for their survival, such as food and reproduction.
Thanks to their flight capacity and their extraordinary sense of orientation—which combines the perception of the Earth's magnetic field, the stars, and other environmental phenomena—migratory birds can travel thousands of kilometers, crossing continents, oceans, and even hemispheres and major natural obstacles such as mountains, deserts, and seas, demonstrating surprising physical endurance and navigation precision.
But how many birds cross our skies in these massive displacements?
Although it is difficult to obtain exact figures, various studies and estimates by ornithologists allow us to approximate the volume of this migration. In our region, it is estimated that the main migratory species include:
• 900 million willow warblers (Phylloscopus trochilus)
• 375 million wood buntings (Emberiza arborea)
• 260 million European pied flycatchers (Ficedula hypoleuca)
• 250 million barn swallows (Hirundo rustica)
• 40 million birds of prey (such as Milvus milvus and Accipiter spp.)
• 700,000 white storks (Ciconia ciconia)
• Etc, etc.
Adding these data, it is estimated that nearly 5 billion birds make this journey between Europe and Africa in each migratory cycle.
This exodus that crosses our skies twice a year not only represents a physiological and behavioral achievement of the species, but also a key indicator of the health of global ecosystems and ongoing climate change.
And it is astonishing that such a huge number of creatures crossing the skies of our planet in a silent and majestic spectacle often remains invisible, like a secret kept high above, waiting for someone to discover it.
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