Bird's nest & eggs ID please!

During the winter my pots of ferns are taken down from my "fern wall" and relocated on the ground under the pergola, protected with a thick layer of wild ferns fronds.
This morning, as I had just started moving those pots back to the "wall", I was surprised to see a small bird frightened fly away from the corner where the pots sat. I then discovered this nest with 5 eggs, inside the pot of my Crested Japanese Painted Fern!
I took the pic and re-installed the cover of old fronds, in the hope that the frightened bird will return to its nest... There is no hurry for me to relocate the pots anyway, I can wait.
Can any of the bird lovers on this forum ID those eggs?

You are invited to a virtual visit of my garden (in English or in French).
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If you live in Derbyshire, as I do.
American Robins are beautiful and about the size of a Blackbird.
One turned up in Bingley.back in 2007 and spent 5 weeks in one of the local gardens.