Jóvenes de Gorrión molinero (Passer montanus) parasitando nidos de su propia especie

Abstract

Juvenile Tree Sparrow (Passer montanus) parasiting nestlings of their own species
Fledging Tree Sparrows have been obseved entering Tree Sparrow nests still occupied by nestlings. These birds seem to be fed by adults, and to remain in the nests for some time. They are so considered as intraespecific parasites.