blue tit eggs

[craigdaniel]

incubation 16 days now whats the latest the eggs could hatch

[Elizabeth B]

The BTO says 13-15 days for incubation: BTO BirdFacts - Blue Tit
My Collins guide says 12-16, and looking at our records since 2001 12 days seems to be the usual time for us.
(The Overview page of our Diary gives the dates of significant events in our boxes).

It's not always easy to tell exactly when incubation has started - the female usually roosts in the box when she starts laying, or often earlier than this, but although she sleeps on the eggs, she's not incubating them.