From the 1970s to 1980 the population of birds called martin fishermen has decreased. Probably these birds have been poisoned with heavy metals that pollute the rivers.
The English ornithological organization BTO has recently given data on birds of the last 30 years. The main conclusion is that the population of most conventional species has declined.
The use of pesticides and the laboreo calendar are the main causes of the decline. The seeds eaten by fins, txokos and wheat verges are treated by herbicides. Planting more and more in autumn and less in spring is another obstacle for birds.
Likewise, the growth of monoculture has reduced the differences between the lands, thus affecting the slopes, white owls and green birds. However, due to monoculture, some species have won, but the winners have been very few.