WhenToBird

Larus californicus · Laridae

When Do California Gulls Arrive in Colorado?

Adult California Gull
Photo: Madeleine Claire, CC BY 4.0 via iNaturalist

California Gulls are winter birds in Colorado: they arrive in early March, peak in early November (4.9% of checklists), and most are gone by mid December.

When to look

First arrivalsMar 1-7early March
Common byMar 1-7early March
PeakNov 1-7early November
Most gone byDec 15-21mid December

Best: early November. First arrivals early March; most are gone by mid December. Peak: on about 4.9% of Colorado checklists.

  1. Januncommon
  2. Febuncommon
  3. Marcommon
  4. Aprcommon
  5. Mayuncommon
  6. Jununcommon
  7. Julcommon
  8. Augpeak season
  9. Seppeak season
  10. Octpeak season
  11. Novpeak season
  12. Deccommon

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

0%2%4%6%Jan 1-7: 0.8% of 32254 checklistsJan 8-14: 0.6% of 23278 checklistsJan 15-21: 0.6% of 22933 checklistsJan 22-31: 0.4% of 30856 checklistsFeb 1-7: 0.3% of 21464 checklistsFeb 8-14: 0.3% of 22910 checklistsFeb 15-21: 0.3% of 28739 checklistsFeb 22-28: 0.8% of 21833 checklistsMar 1-7: 1.5% of 23066 checklistsMar 8-14: 2.1% of 23783 checklistsMar 15-21: 2.7% of 24797 checklistsMar 22-31: 3.1% of 38439 checklistsApr 1-7: 2.8% of 31676 checklistsApr 8-14: 3.0% of 35092 checklistsApr 15-21: 3.1% of 36778 checklistsApr 22-30: 2.1% of 50885 checklistsMay 1-7: 1.4% of 44186 checklistsMay 8-14: 1.0% of 49011 checklistsMay 15-21: 1.1% of 40784 checklistsMay 22-31: 1.1% of 53073 checklistsJun 1-7: 1.7% of 32432 checklistsJun 8-14: 1.3% of 29978 checklistsJun 15-21: 1.7% of 29457 checklistsJun 22-30: 1.8% of 36072 checklistsJul 1-7: 1.7% of 28857 checklistsJul 8-14: 1.8% of 27224 checklistsJul 15-21: 2.3% of 27629 checklistsJul 22-31: 2.6% of 37318 checklistsAug 1-7: 2.7% of 25893 checklistsAug 8-14: 3.5% of 24870 checklistsAug 15-21: 3.9% of 24035 checklistsAug 22-31: 4.3% of 35691 checklistsSep 1-7: 4.2% of 27068 checklistsSep 8-14: 4.2% of 26709 checklistsSep 15-21: 4.5% of 26098 checklistsSep 22-30: 4.4% of 31550 checklistsOct 1-7: 3.6% of 24110 checklistsOct 8-14: 3.8% of 23352 checklistsOct 15-21: 4.6% of 21895 checklistsOct 22-31: 5.1% of 28319 checklistsNov 1-7: 4.9% of 21698 checklistsNov 8-14: 4.8% of 21061 checklistsNov 15-21: 3.6% of 19855 checklistsNov 22-30: 3.4% of 25798 checklistsDec 1-7: 3.0% of 18626 checklistsDec 8-14: 2.2% of 19004 checklistsDec 15-21: 1.4% of 23103 checklistsDec 22-31: 1.4% of 30802 checklistsJanFebMarAprMayJunJulAugSepOctNovDec
Share of complete checklists reporting it, by week (4 per month). Grey bars: fewer than 10 checklists, not counted.

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.

JanFebMarAprMayJunJulAugSepOctNovDec
today
Second week of November

Each county is shaded by the share of complete checklists there that listed the bird, blended with the weeks either side. Darker is more often. It follows where people watch birds, not how many birds there are. How to read it.

Embed this map on your site

Where in Colorado

Best counties

Share of checklists at the peak
  1. Ouray CountyBest mid November · 211 checklists that week, 10,572 in all37%
  2. Jackson CountyBest late June · 407 checklists that week, 7,472 in all32%
  3. Washington CountyBest the second week of August · 37 checklists that week, 2,511 in all31%
  4. Park CountyBest early November · 155 checklists that week, 11,432 in all26%
  5. Morgan CountyBest late September · 179 checklists that week, 5,181 in all26%
  6. Summit CountyBest the second week of November · 131 checklists that week, 14,176 in all21%

Best spots

Share of checklists at the peak
  1. Horseshoe LakeLarimer County, best the second week of April · 20 checklists that week, 747 in all96%
  2. Ridgway State ParkOuray County, best late November · 59 checklists that week, 1,406 in all93%
  3. Walden ReservoirJackson County, best late April · 47 checklists that week, 546 in all90%
  4. Lake Pueblo State ParkPueblo County, best late June · 37 checklists that week, 1,491 in all86%

Busy spots report more of everything; compare the checklist counts before you drive anywhere.

Best time of day

In Colorado, the California Gull is most often listed on checklists started between 11 am and 1 pm (2.5% of those checklists).

0%1%2%3%12 am: too few checklists (512) to judge1 am: too few checklists (468) to judge2 am: too few checklists (513) to judge3 am: too few checklists (656) to judge4 am: too few checklists (1918) to judge5 am: too few checklists (16045) to judge6 am: 2.4% of 71991 checklists7 am: 2.2% of 159189 checklists8 am: 2.4% of 177206 checklists9 am: 2.4% of 165269 checklists10 am: 2.5% of 141029 checklists11 am: 2.5% of 115283 checklists12 pm: 2.5% of 96068 checklists1 pm: 2.5% of 89512 checklists2 pm: 2.5% of 86319 checklists3 pm: 2.4% of 82496 checklists4 pm: 2.4% of 71648 checklists5 pm: 2.5% of 52445 checklists6 pm: 2.2% of 40199 checklists7 pm: too few checklists (24246) to judge8 pm: too few checklists (7986) to judge9 pm: too few checklists (2004) to judge10 pm: too few checklists (888) to judge11 pm: too few checklists (450) to judge12a3a6a9a12p3p6p9p
Share of checklists started in each local hour that reported it. It reflects when people go birding as well as when birds are active. Grey hours have too few checklists (under 2% of the state’s, or under 200) to judge.
Week-by-week table
MonthDays 1-78-1415-2122-end
January0.8%0.6%0.6%0.4%
February0.3%0.3%0.3%0.8%
March1.5%2.1%2.7%3.1%
April2.8%3.0%3.1%2.1%
May1.4%1.0%1.1%1.1%
June1.7%1.3%1.7%1.8%
July1.7%1.8%2.3%2.6%
August2.7%3.5%3.9%4.3%
September4.2%4.2%4.5%4.4%
October3.6%3.8%4.6%5.1%
November4.9%4.8%3.6%3.4%
December3.0%2.2%1.4%1.4%

Neighboring states

  • Wyoming: arrives early March, in the same week than Colorado
  • Utah: year-round, peaks the second week of April
  • South Dakota: arrives early March, in the same week than Colorado
  • Montana: arrives late February, 1 week earlier than Colorado

Common questions

When do California Gulls arrive in Colorado?
California Gulls are winter birds in Colorado: they arrive in early March, peak in early November (4.9% of checklists), and most are gone by mid December.
When do California Gulls leave Colorado?
Most California Gulls have left Colorado by mid December, when reports fall below half their usual rate. Stragglers are still reported until late December.
When is the best time to see a California Gull in Colorado?
The California Gull is reported most often in early November, on about 4.9% of Colorado checklists.
Where in Colorado are California Gulls seen most often?
By county, Ouray County, Jackson County, and Washington County have the highest peak reporting rates for the California Gull (counties with at least 200 checklists).