Iowa City, IA, USA
This picture was taken by my son in Waukee, Iowa. The nest is in his fireplace vent. He has seen a house finch entering and exiting the nest. I have two issues:
1) I think the bigger eggs, including the speckled ones and the almost pure white one, are all house finch eggs. My friend thinks the speckled ones are brown-headed cowbird eggs. What do you think?
2) What in the world is the smaller. beige egg?
Your assistance will be appreciated.
Hello Ben. I think I found out your mysterious egg layers!
For one, those bigger speckled eggs are indeed Cowbird eggs. It is very common to find Cowbird eggs in a house finch nest actually. The white one is a house finch egg, one way you can tell is because of the purplish – gray spots on the wider end of the egg. And last, I think the beige egg is a chimney swift. I hope this is helpful! Good luck birdwatching!
Hi Ben, The three speckled eggs are indeed Brown-headed Cowbird eggs. Brown-headed Cowbirds are a native, protected species that lays eggs in other birds’ nests rather than build their own. This behavior is seen in several species across the world. That said, cowbird chicks tend to do poorly in House Finch nests, as House Finches are one of the few North American songbirds that feed their young a primarily vegetarian diet. Cowbirds tend to need the protein from insects that most other songbirds feed their young. If you haven’t already, we encourage you to report this nest to NestWatch.
The two pale eggs are both House Finch eggs. You’re just seeing the variation in size, and possibly the angle makes it look smaller (seeing the wider end versus the side view). It’s common for eggs to get smaller and less speckled as the female lays more in the clutch. Hope that helps.
The speckled eggs are Brown-headed Cowbird eggs for sure and as a native species, the Brown-headed Cowbird is protected under the Migratory Bird Treaty Act, and taking eggs is illegal. So any person who violates the Migratory Bird Treaty Act by murdering baby cowbirds is subject to a criminal penalty of up to $5,000 for each bird unlawfully taken or possessed; civil restitution fee for each bird unlawfully taken or possessed; and. license suspension or revocation. The white egg is a House Finch egg, and I believe is a Chimney Swift.
*The beige egg is a Chimney Swift