It is one of the first North American bird species to lay eggs, and normally has two to three broods per breeding season, which lasts from April to July. The female builds the nest alone.
A new nest is built for each brood.

A clutch consists of three to five light blue eggs, and is incubated by the female alone. The eggs hatch after 14 days, and the chicks leave the nest a further two weeks later. --- Wikipeadia

The colour of eggs. http://www.ccmr.cornell.edu/education/ask/index.html?quid=503