Bluebird and Small Cavity Nester Conservation
Sialis - Bluebirds and other small cavity nesters



Dwarf or Runt House Wren Egg

Dwarf HOWR egg. Zimmerman.
Above: Dwarf House Wren egg next to sunflower seed. See higher resolution version.
dwarf HOWR egg. Zimmerman.
dwarf HOWR egg. Zimmerman.
Above, left: Dwarf egg (broken) next to a normal House Wren egg from a different nest.
Above, right: Dwarf egg next to a second normal House Wren egg found in the same nest.

I found this dwarf House Wren (HOWR) egg in a nest on July 11, 2009, next to a normal sized egg. The dwarf egg had unusual pigmentation, in that it was evenly spotted and dark. Most HOWR eggs have a wreath on the large end, which is apparent in the lower left photo of an egg from a different nest. (The second egg in the nest I found the dwarf egg in was darker.) I don't know which egg was laid first.

Unfortunately, in my excitement, I took a crummy photo (below, right) of the two eggs side by side and then dropped the normal egg and it broke. Later (before taking the picture at the lower right), my husband broke the dwarf egg on the gravel driveway, and the contents drained away, so I was not able to determine whether the dwarf had a yolk in it. If it DID have a yolk, I would call it a runt (vs. dwarf) egg.

Dwarf eggs are not common. They often lack a yolk. In an egg without a yolk, an embryo would never form, so it would not hatch. They may be more spherical than a normal egg, and have a thick, rough shell (this one did not have a rough shell). See more info on weird eggs.


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