We have 11 bluebird houses and it is my habit to check on them daily to assure that I don't have sparrows trying to build in the houses. This year we have an unusual nest. It's a typical bluebird nest with soft grasses and a nice deep cavity in the center. It has no feathers in the nest which would indicate that it is a tree swallow nest. The 4 eggs were white! I've observed what looks like a bluebird emerging from the box just about every morning. She is very wary and won't let me get anywhere close to get a better look. This morning 2 of the eggs had hatched and they look like typical bluebirds.
I've never seen white bluebird eggs before. They've always been a very lovely medium deep blue color. Has anyone else observed this? Does it indicate a nutritional deficiency? If so, the chicks look normal.
Axel: Thanks a lot for that link. It has amazing information on bluebirds that will make for interesting reading. With an incidence of about 5%, it's a bit strange that I haven't seen this before in the 12 years we've had bluebirds nesting here.
Linda- I have looked at and handled 1000s of seabird eggs over the last few decades and very occasionally you see an anomaly. Usually it's just a single egg in a clutch rather than all the eggs. For example, at very low rates, gulls and terns will produce a blue egg instead of a brown/green speckled one.
John: Interesting! The link that Axel provided indicates that in bluebirds the entire clutch will be white rather than just one egg. If there are mixed egg colors, it may mean more than one hen is laying in the nest. And the link stated that it seems to be permanent so that it will lay white eggs in future clutches. It seems we have a new bluebird pair in the neighborhood! I'll have to ask around to the other 2 neighbors with houses if they have seen this before.
Bluebird egg color
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