On a recent rainy Tuesday, Jim Whatton was inside the National Museum of Natural History in Washington looking for a bird. He opened a drawer and pulled out a preserved barn owl. He laid it next to two other owls resting on a table. He then picked up a feather he had received in the mail and, like a forensic detective, proceeded to match the evidence with the culprit.

“When the stripes line up perfectly, you know you’ve got it,” said Whatton, a Smithsonian research assistant with the Feather Identification Lab, which identifies winged creatures involved in airplane strikes in an effort to protect similar birds.

Whatton held the brown-and-white feather over the wing of a great horned owl. The patterns were different. He moved onto the barred owl. Still not right. He repeated the experiment with the third specimen. “The barn owl is the match!” he said triumphantly.

Whatton performs his identification duties in the museum, not far from where visitors gaze at the Hope Diamond and size up the T. rex. However, the public might never see him or his bird samples. His lab is tucked away in a hidden section of the building that is filled with millions of specimens, artifacts and other items. Scientists use these materials to better understand the natural world.

One researcher is trying to determine whether the silk produced by worms can be used in space. Another scientist is studying beetles that pull water out of the air, a mechanism that could help people living in very dry environments. Other experts are exploring evolution, climate change, biodiversity and conservation.

“We’re not just in the entertainment and education business,” said Floyd Shockley, the collections manager for the museum’s department of entomology. (Before the coronavirus pandemic, Shockley led tours of the insect collection. He hopes to resume the visits once it’s safe.)

The Smithsonian Institution has nearly 155 million objects. Most of the items — about 146 million — belong to the Museum of Natural History. Less than 1 percent of its collection is on display. The rest resides in a giant storage facility in Suitland, Maryland, and in a maze of rooms in the east and west wings of the museum.

“We have one of the most comprehensive collections in the world,” said Rebecca Johnson, associate director for science and chief scientist at the museum. “We collect more than one because [specimens] might look different — males and females, ages, different colors.”

The items are grouped by department, such as botany, anthropology, mineral sciences and entomology. The insects, which are in entomology, are so plentiful, they take up three floors. On the sixth floor, where the flies and aquatic insects are kept, Shockley removed a tray covered in stalk-eyed flies. The insects came to Washington from around the world, including Mozambique, Nigeria and Ghana. Some of the flies are more than 50 years old, which isn’t that old in museum years. A small parasitic wasp dates from 1819.

Sometimes the scientists’ work leads them out of their collection and into another department. One of the envelopes Whatton had received didn’t contain the usual feathers and bones. After inspecting the wing parts, he knew the specimen wasn’t a bird. It was a cicada.

This is part of a series about the Smithsonian, which celebrates its 175th birthday August 10.