Colorado Birding CHallenge


Birding for Conservation

The Colorado Birding Challenge is a fun, county-based birding and conservation event held during the most exciting time of the birding year. Each year in May several billion birds migrate into and through the United States and dozens of species begin to establish breeding territories in each county in Colorado.

Donate / Pledge

The 2022 Challenge supported the Gunnison Basin-Sagebrush Ecosystem Alliance. Directly support and learn more about their efforts.

Big Day: 20 May 2023

The objectives of the Challenge in 2023 are:

    • To engage hundreds of birders in a fun day of finding and learning about Colorado's birds.
    • To raise funds for conservation. The conservation project is being determined now and will be announced in winter 2022/23.
    • To generate eBird data for all 64 counties on the same day.
    • To provide support for the expanding programs and work of Colorado Field Ornithologists.

It's a Team Effort

Teams of 2-4 members (restrictions do not apply to the non-competing category) will bird during the 24 hours within a single Colorado county of their choice. The goal is to record the highest number of species relative to a handicap value determined for the county they are birding in. All teams, other than those in the non-competing category, must abide by the ABA Big Day Rules. 

All participants are asked to solicit donations and pledges per bird species observed during the Challenge to help support a specific conservation project each year.

At the end of the day, every team submits their species list and CFO will calculate the par score for the teams and teams will be ranked by this score. The winning team in each of the five competing categories will be recognized in CFO communications, honored at the CFO Annual Meeting, and will receive a certificate.

Choose a Category


The classic Big Day

Big Sit

Birding by Par

Not all Colorado counties were created equal. Some are large, some are small, some are urban, some are rural, some have diverse habitats, some not so much.

CFO has developed a handicap system based on a decade of eBird data that will establish "par" for each county. This par is essentially the total number of species that one would expect to find in that county at that time of year.

Teams will be scored according to the total species they observe divided by par for the county they birded. Teams will be ranked by the total percentage of par they score.

This is a novel approach and there are some obvious challenges, such as the disparity in data between heavily birded counties like Boulder, Denver and Larimer vs. much less birded counties like Huerfano, Moffat or Sedgwick. If anything, we hope this will motivate teams to select these under-birded counties! 


Colorado Field Ornithologists invites applicants to submit proposals to be the beneficiary of each year's Colorado Birding Challenge. Proposed projects should have a lasting benefit to Colorado birds or the habitats on which they rely.

More than $75,000 has been raised and donated for conservation efforts through the Challenge since 2021.

The deadline to submit a proposal for 2023 was Wednesday, November 30, 2022.