Winter Classification Flights

Winter weather conditions typically concentrate pronghorn, deer and elk and provide increased visibility for staff who are conducting the aerial surveys.
Video: Flight for Wildlife

Wildlife managers, biologists, and researchers from Colorado Parks and Wildlife are gearing up for a busy winter season. During the winter months, Colorado Parks and Wildlife will be using helicopters and fixed-wing aircraft to capture and classify big game species. 

Winter study work will include operations to capture, assess, and collar elk, deer and pronghorn in the Bears Ears, White River, Roaring Fork, Steamboat Springs and Middle Park areas.

A doe deer wearing GPS collar as part of a wildlife study.
A doe deer wearing GPS collar as part of a wildlife study.

The elk studies are in the second year of a six-year study. Colorado Parks and Wildlife is capturing and collaring adult female elk and calves to assess the health of herds, estimate survival rates, identify major sources of mortality, and evaluate the influence of human recreation on elk herds. Mule deer studies are conducted annually to assess survival rates and monitor seasonal movements. A pronghorn movement study will begin in Middle Park this winter. Colorado Parks and Wildlife will capture and collar 40 female pronghorn to assess migration patterns, herd connectivity, and seasonal movement patterns to aid in conservation efforts. 

Why Winter?

pronghorn
Winter weather conditions typically concentrate pronghorn, deer and elk and provide increased visibility for staff who are conducting the aerial surveys

Winter classifications – often thought of as “counts” – will take place December through February; utilizing helicopters and fixed-wing airplanes. These classification flights occur statewide. It’s not possible to count all of the deer and elk across the landscape, so Colorado Parks and Wildlife staff classify animals by age and sex to determine the health of the herds and to compare to objectives in herd management plans. These operations provide wildlife managers with supplementary data that is used to generate computer models that estimate wildlife population numbers and composition.

While animals are under pressure to survive harsh winter conditions, winter remains the best time of year for the success of these operations and the overall long-term health of big game herds. 

Counting from helicopter
Annual aerial inventories help estimate population, productivity and distribution of animals throughout the state.

“Winter is the safest time to conduct capture work,” explained Nathaniel Rayl, a big game researcher for Colorado Parks and Wildlife. “Cool ambient temperatures and moderate snow depths help prevent overheating and injury when capturing big game species with a helicopter.”

Area Wildlife Manager Matt Yamashita oversees the Glenwood Springs Colorado Parks and Wildlife operations. He adds that winter provides other advantages for wildlife flights. 

“Winter weather conditions typically concentrate deer and elk and provide increased visibility for staff who are conducting the aerial surveys,” Yamashita said. “The short duration of flight disturbances is warranted by the important biological information that is gathered.”

Warning: Operating at Low Elevation

low flying helicopter
Helicopters may be operating at low elevation and spend time in one area before moving on to the next survey area.

Northwest Colorado residents are reminded that they may see low flying aircraft during these surveys. Helicopters may be operating at low elevation and spend time in one area before moving on to the next survey area. Colorado Parks and Wildlife contractors and staff attempt to minimize noise or disruption to residential areas. 

Colorado Parks and Wildlife manages more than 400,000 deer, nearly 300,000 elk, 82,000 pronghorn, about 3,000 moose and hundreds of other species. Management of big game species provides millions of dollars to Colorado’s economy each year through hunting revenues for communities and small businesses. In addition, revenue from big game hunting is responsible for the introduction, reintroduction, and conservation of dozens of non-game species in the state.


Randy Hampton is the public information officer for CPW’s Northwest Region. Randy based in Grand Junction, Colorado.

4 Responses

  1. Other states also use data from the hunters to determine the number of animals in the field. This could be another valuable tool used to get a more accurate count of the animals.

    1. Thanks Ron. We also use hunter harvest surveys in the calculation. It’s all part of a pretty complex modeling process. I think we’ve got a video somewhere on the modeling process… if I can find it, I’ll post that link. Stay well and Happy Holidays!

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