What kind of bird builds a small nest and lays 3 small blue eggs and 1 speckled egg?

there are two birds in the process of this: the house finch and the brown-headed cowbird. the house finch is the one that built the nest and laid the blue eggs. however, that speckled egg was laid by the cowbird. the cowbird does this to use finches to raise their own children, not really regarding the harm caused to the baby finches.