An owl that died about 47 million years ago in what is now Germany still has its last meal inside it, and that meal is reshaping when scientists think owls became creatures of the night. Researchers describe the bird as a new species, Masillastrix blattophaga, in a study published Nov. 2 in Current Biology.

Inside the fossil's stomach region were greenish-blue, iridescent wing fragments from a cockroach — the owl's apparent last meal. Shiny, iridescent coloring in insects is associated with daytime activity, so the find suggests this early owl was hunting in daylight.

Combined with clues from its bones and feathers, the authors estimate that owls shifted to nighttime habits sometime between about 47 and 34 million years ago. The evidence comes from a single specimen, and the researchers acknowledge the timing is a best estimate.

A 'Last Supper' Preserved in Lake Mud

The fossil comes from the Messel Pit near Darmstadt, a UNESCO World Heritage Site where an ancient forest lake preserved animals in remarkable detail. Apart from its missing skull, the bird's skeleton is complete, and even its flight and tail feathers survive, the Senckenberg research institute said. It is only the second owl species known from Messel.

"Apart from the skull, the bird's skeleton is complete and exceptionally well preserved," Mayr said, translated from German. He worked with co-authors Lucia Šmídová, Adrian Richter and Wedmann.

The bird was small, about 12 centimeters (5 inches) long. Its name translates loosely as the cockroach-eating owl of Messel, combining the Latin name for the site with a reference to its insect meal.

Sonja Wedmann, who leads Senckenberg's Messel excavations, identified the stomach contents as cockroach wing remains from the pattern of their veins. A better-preserved, very similar cockroach turned up a few meters away at the same dig site, supporting the identification. "This means the cockroach in the little owl's stomach provides an important clue to its own activity time," lead author Gerald Mayr said in the institute's release, translated from German.

Reading Behavior From a Meal

Messel offers unusual conditions for that kind of detective work. During the middle Eocene, central Europe sat in a warm greenhouse climate, and the lake was ringed by subtropical forest. Oxygen-poor water at the lake bottom slowed decay, which is why the site preserves soft tissues, feathers, and even the original colors of some insects.

Stomach contents are rare in the fossil record, and they offer a direct look at what an animal was doing just before it died. In this case, the prey's appearance carries the signal. Iridescence comes from microscopic layered structures that reflect light at different angles, producing the shimmering green-blue preserved in the Messel cockroach wings. Many modern insects with bright, iridescent wings are active by day, when color plays a role in signaling and camouflage.

The bones point the same way. The owl's upper wing bone, the humerus, is sturdier than in modern owls, Live Science reported. Today's nocturnal owls have long, slender wing bones and specialized feathers that allow nearly silent flight, an advantage when stalking prey in darkness but less important by day. The fossil's flight feathers lack those features.

Earlier owl fossils also show bony ridges above the eye sockets that may have shaded the eyes from sunlight, and head-rotation structures similar to those of daytime raptors. The oldest known owl with modern wing-bone proportions lived about 35 million years ago in France, which helps set the later end of the transition window.

Limits of a Single Fossil

The cockroach evidence has limits — and the authors say so. The owl could have caught its meal at dawn or dusk, when both day-active insects and twilight hunters are on the move, which would weaken the case for strict daytime hunting. One fossil cannot show how an entire group behaved.

"There exists a consensus that owls must have evolved from a diurnal ancestor," Mayr told Live Science. The new specimen adds direct evidence to that consensus and narrows when the shift happened. The study is peer-reviewed, but the owl fossil record is sparse, and many species are known only from a few isolated bones.

Why owls became nocturnal remains unresolved. Earlier ideas, such as escaping competition from daytime raptors or exploiting night-active mammals, fit poorly because both of those groups diversified later, around 20 to 25 million years ago. "By narrowing down the time frame when owls became nocturnal, our study may eventually contribute to solving this mystery," Mayr said.

Night Vision and Silent Wings Came Later

Modern owls are among the most specialized night hunters on Earth. Large, forward-facing eyes gather dim light, asymmetrical ear openings in many species pinpoint sounds in three dimensions, and soft-edged feathers muffle the sound of flight. The Messel owl suggests these traits developed after the earliest owls were already established.

The oldest known owl, Ogygoptynx wetmorei, dates to about 60 million years ago, shortly after the extinction of the non-avian dinosaurs. That leaves millions of years in which owls may have lived very differently than the silent nighttime hunters familiar to backyard birders today. Some living owls, such as the burrowing owl and northern hawk owl, still hunt regularly in daylight, a reminder that nocturnality is common among owls but not universal.

Messel continues to yield discoveries, and Senckenberg teams excavate there each year. Future finds, especially owls with preserved skulls, eyes, or ear regions, could test the new timeline. "We still know so little about the early evolution of modern birds," Mayr said.

What Readers Want to Know

What did researchers find? A 47-million-year-old owl fossil from Germany's Messel Pit, named Masillastrix blattophaga, with iridescent cockroach remains in its stomach region.

Why does a cockroach matter? Iridescent insects are associated with daytime activity, suggesting the owl hunted in daylight rather than at night.

When did owls become nocturnal? The researchers estimate between about 47 and 34 million years ago, based on this fossil and later owls with modern wing proportions.

Could the owl have eaten at dusk instead? Yes. The researchers note the meal could have been caught at dawn or dusk, which is a key limitation of the evidence.

What other clues point to daytime habits? Its sturdy wing bones and flight feathers lack the features modern owls use for long, silent flight at night.

How old are the oldest owls? The oldest known owl, Ogygoptynx wetmorei, lived about 60 million years ago.