An exceptionally well-preserved, approximately 47-million-year-old owl fossil from the UNESCO World Heritage Site Messel provides new clues as to when owls became nocturnal. The newly described species Masillastrix blattophaga was likely still diurnal—as indicated by an iridescent cockroach in its stomach, as well as the structure of its feathers and wing bones. In their new study, published in the journal Current Biology, the Senckenberg researchers speculate that nocturnal behavior in owls only developed between the middle and late Eocene, some 47 to 34 million years ago.