Expert: Roger Lederer - 5/11/2010

Question
QUESTION: My bluebird nest had 5 eggs on 4/14/10 and the female was sitting on the eggs. I left for a trip and came back on 4/21/10 and there were 7 eggs in the nest. there is now 9 eggs in the nest and also one egg in a nearby nest box. In 20 years i never had more than  eggs in a nest. What is going on?
Thank you

ANSWER: There are two explanations. Either another female laid her eggs in this nest, which I find unlikely, or the original female decided the original eggs were not fertile or were not developing properly and decided to lay another clutch. You may know that most clutches or bluebirds are fathered by more than one male, so sometimes the female ends up laying two clutches in one nest.

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QUESTION: four of the eggs hatched and the young were being fed for about a week. Now the entire nest is empty and no trace of the young or the unhatched eggs remain. what could possibly have happened for everything to disappear?
Thank you

Answer
I can't give you a positive answer because I haven't observed the situation. If there were nine eggs in the nest and only four hatched and a week later everything is gone (is that correct?) then a predator got all of them. That's really the only logical explanation.