Two young bald eagles swooped near the face of the Clinton Lake dam, just within view of a large cluster of ducks taking refuge Saturday morning in a swath of open water.

David Seibel, a Johnson County Community College professor, trained a large scope on the ducks. He prepared to tally their numbers and species as part of the annual Christmas Bird Count, a campaign organized by the National Audubon Society and Jayhawk Audubon Society to take stock of area bird populations. Though huddled in large numbers, danger loomed.

“This time of year eagles eat about anything,” Seibel said. They prefer fish, he added, but will switch to ducks when the fishing is no good. “To my mind that’s where the phrase ‘like sitting ducks’ comes from.”

Just before 9 a.m., Seibel arrived at the dam with one of his JCCC students, Amelia Mallett-Kass, of Lawrence, and fellow birder Mick McHugh, of Kansas City, Kan. Each wore multiple layers to guard against the wicked gusts of cold air coming off the lake, their first stop of a campaign expected to span until dusk. As the sun set, all counters planned to convene for a chili supper, at which point final numbers would be tallied and observations would be shared. Counters planned to visit 12 locations within a 15-mile radius by day’s end, Seibel said.

Mallett-Kass joined her professor for a tradition he’s taken part in since 1969 — 33 of those years featuring stops in Lawrence before a Sunday count in Perry. She was a quick study, picking up on counting the birds in groups.

“That’s exactly right,” McHugh said. “You count certain areas and just go sideways.”

At least early on Saturday, Seibel expected the overall count to be on the low side because of recent cold temperatures in the area.

“It’s a tiny piece of a really big puzzle,” Seibel said of the count. “But all these pieces add up to a lot of information.”

Through their scopes and binoculars, the three counted up to 300 mallard ducks, 50 ring-billed gulls and about a dozen herring gulls at the lake. They also settled on a total of six bald eagles. Mallett-Kass and McHugh eventually warmed up in the Jeep and waited to leave for their next viewing point. But Seibel remained focused on the stilled group of ducks, among which were the rarer goldeneye duck and what looked like a green-wing teal, one of the smallest ducks.

“We need to boogie,” McHugh said out of the open passenger side door. “We’ve got too much land to cover today.”

With that, the ducks dispersed. “Oh!” Seibel shouted as he discovered the source of the disturbance. One of the young bald eagles had taken hold of a mallard duck and plunged the duck underwater, drowning it.

“David,” McHugh said, “have you ever seen that before?”

“No,” Seibel said, “I haven’t.”