Sparrow Plagues in Extremadura (Western Spain) Over Four Centuries (1501–1900): A Spatio-Temporal Analysis of Records From Historical Archives

Some bird species can cause crop damage but the historical variation in the incidence of such events is poorly documented. We analyse the spatio-temporal variation of damage attributed to sparrows (Passer domesticus, P. hispaniolensis and/or P. montanus) at a regional scale in Extremadura (western Spain) over four centuries (1501–1900). Textual data were extracted from historical documentary sources using over 12,000 Books of Accords (Libros de Acuerdos) belonging to 203 municipal archives. Sparrow agricultural damages were estimated from reported actions to control sparrow populations and two simple indices were constructed to analyse the spatial (PIM) and temporal (PIY) variation in sparrow plagues. We used these indices to fit geostatistical models and analyse time curves. We found 251 accords reporting sparrow plagues, distributed across 236 years and involving 47 municipalities. Most of these reports (97.2%) were mandatory impositions (repartimientos) on residents to deliver a certain number of dead sparrows within a fixed period, under penalty of a fine or imprisonment. Results show a significant spatio-temporal variation in sparrow plagues, which we tentatively relate to dynamic environmental and agroecological factors. The spatial index showed high values (PIM > 4) in certain cereal-producing areas, among which La Raya zone located in western Badajoz province was the best example. The temporal index reached maximum values (PIY = 7.3) in the mid 18th century (1741–1770), probably because this was a milder period (within the so-called Little Ice Age) coinciding with increased food availability for birds. In addition, we also examine some sociopolitical, economic and historical features that could have shaped the plague indices. We particularly discuss the normative and legislative developments (e.g. mandatory impositions), the municipal activity itself (affected by wars and other historical events) and the bird conservation interest (which flourished during the final quarter of the 19th century). We conclude that textual data-based indices provide a suitable historical perspective of the agricultural impact of sparrows in Extremadura and of human perceptions of them.