Urban sparrows have lost 20% of their population since 1998. The decline is more pronounced in urban areas than in rural areas.
The most available junk food in cities is junk food, which we throw away. The diet is poor and does not contain the necessary amounts of amino acids and vitamins, researchers say. It is difficult for such as seeds or invertebrates in green areas to find healthy food. The research offers physiological data on the species, but it is not decisive when it comes to specifying the role that nutrition plays in reproduction and population decline.