We have all seen American Robins build their nests very close to houses, or even on them. Usually these nests are in well-protected spots, for example under the eaves of a house. Even if the nest is right by a doorway where people enter and exit, the young robins usually fledge successfully.
This American Robin successfully fledged four young from a nest on an outside lamp fixture.
Sometimes, though, an inexperienced female will choose a nest site that is too exposed, leaving the eggs or young vulnerable to predators. Two years ago, my sister-in-law discovered this nest on the end of a beam at her house near Bragg Creek, SW of Calgary.
This shot seems to show that there were four eggs in the nest. Photo by Sharon Thompson.
Within a couple of days, however, Common Ravens had found the nest and taken all the eggs. The robin abandoned it, and presumably learned a lesson about the importance of location.
A few weeks later, we noticed that the nest was no longer empty – a second nest had been built inside of it. There were no eggs, and no bird was seen in it. Probably the ravens had got to this one too, as it looked like they had messed up the nesting material in the process of robbing it. We managed to take the nest down to have a closer look.
Nest in a nest.
We took the inside nest out. Here are the two side-by-side:
The robin nest was beautifully constructed. The birds had gathered moss from the surrounding forest, and cemented it to the woven cup with mud.
I suspect that the inner nest was made by Chipping Sparrows. A male was singing in the area all spring. The size and material of the nest is also similar to that of a Chipping Sparrow nest I found in my yard in Calgary.
Chipping Sparrow nest in our mugo pine.
The Chipping Sparrow nest after I removed it.
I know that sometimes birds will build one nest right on top of another in the same breeding season, for example if they have been parasitized by cowbirds. But I’ve never seen two different songbirds nestle their nests one inside the other like this before.