Fertile House Ssparrow X Tree Sparrow (Passer domesticus XPasser montanus) hybrids?

Abstract

Viability and a seemingly successful breeding of a Fl House Sparrow x Tree Sparrow hybrid are reported from islands off the coast of northern Norway. From two consecutive clutches of House Sparrow x Tree Sparrow hybrids recorded in 1995, only one of 7 chicks survived the first year. The surviving individual was later, in 1997. round attending the nest with a female House Sparrow and feeding the young in two consecutive clutches. Neither of the F2 hybrids were observed after fledging. Despite the fact that Mouse Sparrows indulge in frequent extra pair copulation, we find it unlikely that both clutches fed by the male hybrid could have been fathered by a House Sparrow male and therefore conclude that the Fl male hybrid was fertile. The hybridisation may have been facilitated by the fragmented structure and small size (from 5 to 100 individuals) of the sub-populations found in our study area.