On the wintering grounds in South America the Cerulean Warbler usually is found in mixed-species foraging flocks, associating with tropical tanagers and other resident species.
When renesting after a failed first nest, the female often uses spider web from the old nest to start construction on the new nest. Fresh lining is gathered for the new nest, but spider web may be too valuable and time-consuming to waste.
The female Cerulean Warbler has an unusual way of leaving a nest after sitting on it a while. Some people call it "bungee-jumping." She drops from the side of the nest, keeping her wings folded to her sides, and opens her wings to fly only when she is well below the nest.