WhenToBird

Common Loon · Gavia immer

When Do Loons Arrive in Colorado?

Adult Common Loon
Photo: Hungry-Sarracenia Photo, CC BY 4.0 via iNaturalist

Common Loons mostly pass through Colorado: they arrive in mid October, peak in the second week of November (4.8% of checklists), and most are gone by early December. They are the only regular loons in Colorado.

When to look

First arrivalsOct 15-21mid October
Common byOct 15-21mid October
PeakNov 8-14the second week of November
Most gone byDec 1-7early December

Best: the second week of November. First arrivals mid October; most are gone by early December. Peak: on about 4.8% of Colorado checklists.

  1. Januncommon
  2. Febrare
  3. Marrare
  4. Apruncommon
  5. Mayrare
  6. Junnot usually seen
  7. Julnot usually seen
  8. Augnot usually seen
  9. Sepnot usually seen
  10. Octcommon
  11. Novpeak season
  12. Decuncommon

Darker months: more checklists report it. Outlined: peak month.

Loons in Colorado, species by species

SpeciesFirst arrivalsCommon byPeakMost gone byPeak %
Common LoonOct 15-21Oct 15-21Nov 8-14Dec 1-74.8%
0%2%4%6%Common LoonJanFebMarAprMayJunJulAugSepOctNovDec
  • Common Loon
Share of complete checklists reporting each species, by week (4 per month). Gaps: fewer than 10 checklists that week.

Frequency is the share of complete checklists in Colorado that listed the bird, 2016–2025. It is not a head count, and it follows where and when people go birding. How to read it.

Where in Colorado

Best counties for Common Loon

Share of checklists at the peak
  1. Sedgwick CountyBest early November · 24 checklists that week, 1,168 in all23%
  2. Crowley CountyBest mid November · 24 checklists that week, 1,883 in all22%
  3. Washington CountyBest the second week of November · 15 checklists that week, 2,511 in all21%
  4. Kiowa CountyBest the second week of November · 58 checklists that week, 3,854 in all21%
  5. Logan CountyBest early November · 51 checklists that week, 4,117 in all16%
  6. Montezuma CountyBest the second week of November · 183 checklists that week, 15,992 in all15%

Common questions

When do loons arrive in Colorado?
Common Loons mostly pass through Colorado: they arrive in mid October, peak in the second week of November (4.8% of checklists), and most are gone by early December. They are the only regular loons in Colorado.
When do loons leave Colorado?
Most Common Loons have left Colorado by early December, when reports fall below half their usual rate.
When is the best time to see loons in Colorado?
The Common Loon is reported most often in the second week of November, on about 4.8% of Colorado checklists.