“Black-winged swallow, where are you going? That you’re flying so high”, begins the lyrics of the song performed by the group Madredeus entitled “A Andorinha da Primavera”. It turns out that these announcers of the new station have been crossing the skies of Portugal less often.
The number of swallows has fallen by 40% in the space of 20 years. This is the main conclusion reached by the census of common birds, a long-term monitoring program for nesting birds, coordinated by the Portuguese Society for the Study of Birds (SPEA).
This decrease is considered representative of the widespread decline of several species of long-distance migratory birds.
In statements to the RenaissanceHany Alonso, SPEA technician and coordinator of the study now published, points to the lack of food as one of the essential causes, as is the case of insects.
“Whether we are talking about climate change or agricultural intensification, it all has to do with food availability. In this case, insectivorous species depend on insects. These small animals end up being the most affected by major changes in ecosystems. In fact, in insectivorous birds we can see this impact, as their numbers decrease”, he points out.
Hany Alonso explains that climate change represents one of the problems already identified, but there are other associated factors.
“A study came out last year that took data from the last 37 years in Europe and evaluated the trends of 170 species. What can be seen is that agricultural intensification was the factor that was most affecting the decline of species, namely through the use of pesticides. One of the logical consequences is, obviously, the reduction of insects”, he maintains.
The SPEA technician also states that in addition to swallows, there are other species of migratory birds on the path to a generalized decline and gives as examples the wild turtle dove, barrete shrike and cuckoo.
In Portugal there are at least five species of swallows. The chimney swallow is a migratory species and one of the most common.
