I checked on the chicks in box #1 today and was surprised. I 3 newly-hatched chicks and 2 unhatched, abnormal bluebird eggs under them in the nest.
I hadn't noticed the abnormal size and shape of these two eggs when I monitored the box earlier this month. (A lesson learned about monitoring: take the eggs out of the nest and put them in your hand to inspect them - even if they look normal in the nestbox). One egg was round and significantly "dwarfed." The other was the right shape (oval), but 3mm smaller than a "normal" bluebird egg.
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| normal egg and the 2 smaller, abnormal eggs |
I removed the 2 eggs that hadn't hatched - and compared them with a "normal" infertile egg I'd removed from a box earlier in the summer. I photographed and measured them.
How to determine if they were fertile? Easy - I cracked them open. Both had yellow yolks - no sign of a developing chick.
The three chicks looked fine.
For more information about weird bluebird eggs, check out the North American Bluebird Society website.
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