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Robins built a nest on a trellis in front of my deck. I was curious and peeked inside when the bird was away. There was one blue egg. A few days later I saw a starling walking around this nest.

Just now, I took another peek inside. This time there were three eggs, but one does not look like the others.

Did the starling lay its egg in this robin's nest? This nest is located in Northern New Jersey.

Robin's Nest with Suspicious Egg

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  • More likely to be a cuckoo.
    – Chenmunka
    May 9, 2023 at 21:04
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    Just to check: Europe/UK? Starlings are widespread and the other side of the Atlantic they have a thrush they call a Robin.
    – Chris H
    May 10, 2023 at 6:00
  • @ChrisH, I updated the question with the location (Northern New Jersey, USA). I was confused by websites that identified these blue eggs differently and realize now that European robins/starlings have different egg characteristics from Northern American ones. Thank you for asking for clarification. May 10, 2023 at 14:22
  • @ChrisH The birds that built this nest are most certainly North American robins - britannica.com/animal/American-robin May 10, 2023 at 14:33
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    @qdread not as distinctive a call as ours, but still we have no evidence of cuckoos at all. The first mention of any cuckoo species was in the context of an assumption that this was in Europe, in the answer below.
    – Chris H
    May 10, 2023 at 14:47

1 Answer 1

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Perhaps there are now eggs of three species - robin, starling and cuckoo.

Starlings do attempt to take over others birds' nests, see European Starling Life History

Starlings often take over the nests of native birds, expelling the occupants.

Optics Mag also says

However, [starlings] are invasive and can take over other birds’ nests and even kill them.

Cuckoos simply lay their egg, and when it hatches, their chick expels the others. The RSPB says

When a female cuckoo finds a suitable nest, and the hosts aren’t looking, she removes one of their eggs and lays her own egg in its place. Cuckoo young hatch after just 12 days, and push the hosts’ eggs or babies out of the nest, allowing it to eat all food brought by the host bird.

Identifying the three similar eggs, the two smaller ones are probably robin and starling. Optics Mag has this picture, which shows that starling eggs are larger and paler than the robin's egg. So the egg at the top of the OP's nest would be starling, with robin on the left.

enter image description here

The cuckoo egg is usually larger than the host's eggs, and is often mottled, such as the selection shown below, from Cosmos magazine. The cuckoo evolves its mimicry according to the other species in its habitat. Its egg will be the one on the right of the OP's photo.

enter image description here

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  • Cuckoos are pretty rare, but they're very vocal with a call that carries a long way. If they're not heard in the neighbourhood in spring, they're quite unlikely
    – Chris H
    May 10, 2023 at 6:02
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    Are we sure the egg on the right in the OP is mottled and not just dirty? It's hard to tell from the photo. May 10, 2023 at 13:13
  • Unfortunately, the only cuckoos in this Northern New Jersey area, where this nest is located, are some of the neighbors. No Cuckoo birds have ever been observed, but I agree the eggs in your example look similar to one in the photo. May 10, 2023 at 14:26
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    I replaced the original photo with new one this is closer and clearer. (The reference locations in this reply no longer point to the same eggs. This new photo is taken one day later and the robin appears to have rotated the eggs 60-degrees clockwise. May 10, 2023 at 14:38

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