The mysterious bird outbreak of 1779 in southeastern Iberian peninsula: a massive irruption of the Spanish sparrow Passer hispaniolensis from Africa?

Several current and past bibliographical references mention the sudden pest outbreak of a mysterious sparrow–like bird in the southeastern Iberian peninsula in 1779. Based on these references, we investigated unpublished documentary sources from various historical archives that reflected the actions carried out by public authorities against the bird pest. Some narratives come from direct witnesses who sometimes provided relevant data on the origin and biology of the birds involved. From the analysis and interpretation of these data, it was clear that the bird outbreak was caused by an unusual passerine in southeastern Iberia. In May 1779, birds irrupted in large numbers into several localities in the current provinces of Alicante, Murcia and Almería, probably coming from North Africa. Damage caused to cereal crops was meaningful and the extraordinary alarm generated in the people motivated the intervention of both local authorities and government institutions. The birds formed large arboreal colonies, building multiple nests per tree. We discuss different hypotheses related to the taxonomic position of these birds within the Ploceidae and Passeridae families. The bird species whose distribution, morphology, life characteristics and behaviour agrees best with the testimonies analysed is the Spanish sparrow Passer hispaniolensis. We propose that this sparrow could be the protagonist of this historic bird pest outbreak.