Complex sentence: Having fledged one brood some rainbow pittas may build a new nest and lay a second brood (two out of four closely studied nests relaid), and may even build the next nest while still feeding the previous brood.
Split into simpler sentences: Having fledged one brood some rainbow pittas may build a new nest and lay a second brood; in one study two out of four closely studied nests relaid. Pairs may even build the next nest while still feeding the previous brood.