Winter Raptor Surveys: 1983 – present

Since 1983 Boulder County Nature Association (BCNA) volunteers have counted wintering raptors along survey routes scattered throughout the plains of Boulder County, Colorado. We initiated the surveys during a time when intensified poisoning efforts by private landowners and government agencies appeared to threaten prairie dog populations in parts of Boulder County. Some of these poisonings were occurring in the Boulder Reservoir area, where Ferruginous Hawks, Red-Tailed Hawks, and Bald Eagles gathered each winter. We wanted to observe the effects of fluctuating prairie dog populations on these and other species. We also hoped to locate wintering raptor concentration areas, such as Bald Eagle roosts, Northern Harrier roosts and large prairie dog colonies, so that these areas could be protected.

Raptor Identification Review

For anyone interested in a raptor ID refresher, Denver Field Ornithologists hosted several useful webinars which can be viewed here:

Raptor Survey Training, Wind Scale Notes, and Survey Routes

Please note: The NatureCounts app is now the primary way to record all data, starting with the 2025-2026 season. We are no longer using the grid system.  Data without precise locations will not be utilized by the county.

NatureCounts App User Guide for Winter Raptor Surveys (pdf; Nov 2025) and recording of the training on YouTube at https://youtu.be/0hLZEdcwj5A

Beaufort Wind Scale for Printing (pdf)

Beaufort Wind Scale (Excel file): Do not survey above wind speeds of 12 mph or 19 km/hr

Raptor Survey Report Form (to be used as a back-up). Please use the NatureCounts app to record all data.  Data without precise locations will not be utilized by the county.  We are no longer using the grid system.

Maps are portions of the actual USGS quads. The downloadable maps for 2014 are all high-resolution PDFs, with one page for the map and a second with a 500-m grid with numeric label.

Winter Raptor Survey Route Distances in km

Link to research data and reports for raptor studies to date 

Banner Photo © Vicki Braunagel

Boulder County Nature Association

P.O. Box 493, Boulder, CO 80306 | Contact Us