Question about incubation timing/habits…

[TimC]

I’m hoping someone might be able to answer this. I’ve looked it up but haven’t found any related info. I’ll start with the back story with the question at the end.

We’re experiencing a long cold spell here and I wonder about a particular nest box I have monitored since 4-19 when I installed the box. Nest materials appeared the next day. On 4-24 two eggs were inside and on the 28th there were five. Today (May 6) there are still five eggs and while sitting on the hill near the box I observed the BB male and female hunting nearby. When a pair of Chickadees showed an interest in the box the bluebirds both flew into a nearby tree and the Chickadees flew off. None of the birds seemed aggressive. They were just exhibiting mild territorial behavior.

As I mentioned we have had temps below freezing each night and daytime temps in the 40s and 50s. Lots of wind as well. Snow cover in the woods has mostly been gone for two weeks. I don’t see much in the way of bugs; flying or crawling (with the exception of wood ticks… I swear they are always here, even during snow melt periods).

So my question… is it necessary for the bluebirds to keep the eggs warm after being laid? I’m wondering if the eggs can be whatever the ambient temperature is until incubation starts. Then they need to be kept warm during active incubation?

---

WI/MI Border, about 100 miles north of Green Bay

Tim C. WI/MI border.

[David in Stafford,VA]

Tim, normally, from what I have read about the Bluebirds and what I have seen with my nests, the female starts to sit on the eggs for 14 days after the last egg is laid. So if your final egg was on April 27, she would be sitting on the eggs until May11 or 12. The female will be on and off the nest during that time but mostly on if the temps stay that low. She may come off periodically to feed and definitely on all night. I have seen my male bird bring food to the nest box while she is still sitting.
Try not to disturb her while she is nesting.

David
Stafford, VA

[tamsea]

What David said.
I don’t know the scientific answer but I do know from experience that they don’t incubate as much as I think they should. Mine are always off the nest! They don’t need to incubate as much as we think. My husband said to me yesterday that he wondered if the eggs froze because she isn’t incubating…and today they hatched.
Mine always hatch in 12 days…don’t know why. So it could be even April 8th that yours should hatch.
The big problem comes when she hasn’t started incubating because she hasn’t finished laying. That’s when I worry about the cold affecting the eggs. Or when she has newly hatched babies that can’t regulate their own body temperature yet.

Tammy

[Author]

Posts