Abstract
We found an uncommonly large clutch of the Tree Sparrow Passer montanus in July 2010. Nine eggs were laid in a nest box at Ogata Village in Akita Prefecture, northern Japan. One egg hatched and successfully fledged, but the other eight eggs remained unhatched. The clutch included at least two eggs different from the others in color and pattern. It is known that Tree Sparrows lay the last egg different from the others of a clutch in color and pattern. The largest clutch ever reported for Tree Sparrows consists of eight eggs. It is, therefore, reasonable to assume that these eggs were laid by multiple females (including parasitic ones) or they belonged to different clutches laid by the same female.
