Savannah Sparrow (Passerculus sandwichensis) Science Article 6
Evidence of intraspecific nest parasitism in passetines is rare although some well documented cases do exist (Yom-Tov et al. 1974, Ibis 116: 87-90). This note describes an incident whose circumstances suggest that two complete clutches were laid simultaneously in the same nest by two female Savannah Sparrows (Passerculus sandwichensis).
PATRICK J . WEATHERHEAD AND RALEIGH J. ROBERTSON, Auk, Vol. 95