Expert: Roger Lederer - 5/20/2007

Question
A pair of house finches built their nest in one of my fuchsia hanging baskets. We noticed that there was one egg that broke on the porch (it was blue shelled). The next time I carefully watered the plant, we noticed that there are 3 blue eggs and one egg that is tan with black specks that is larger than the other 3 blue eggs. Could another bird have laid the different colored egg and kicked a blue egg out of the nest while the mama was out? Is there anything that we should do to ensure the viability of the fledglings?

Answer
It seems that a Brown-headed Cowbird laid an egg in the House Finch nest and it is likely that the female cowbird removed the House Finch nest in the process. Remove the odd egg or the House Finch will end up raising the Cowbird young instead.
Brown-headed Cowbirds are called nest parasites because they do not build a nest or raise their own young; they lay their eggs in other birds' nests and let the host bird do the hard work. They have harmed the populations of several songbirds in this way. Roger Lederer at Ornithology.com