The importance of political, economic, and cultural factors in explaining fundamental ornithological problems (A case study from Bulgaria) III. Sparrows (Passer spp.)

The importance of socio-economic factors in explaining fundamental ornithological problems, some of which are unresolved issues with passerine species, is analyzed, with a special emphasis on Bulgaria. Over the past 150 years, Bulgaria has experienced a number of socio-economic cataclysms that have had an impact on bird life, offering surprising new solutions for European passerine species. The relationship between the Spanish and the House sparrows reveals a temporally differentiated relationship related to the seasonal periodicity in the availability of food resources. The main food reserves are used by a sedentary species, while the seasonal surplus is used by a migratory species with largely similar ecological requirements. The different migratory behavior and the resulting differences in metabolic and molting programs require a clear distinction between the species. The Italian and Cretan sparrows occur where access for the House sparrow was difficult. The Spanish sparrow, as a long-distance migrant, had no trouble getting there and evolutionarily took the position of the sedentary House sparrow.