WhenToBird

Ardea herodias · Ardeidae

When Do Great Blue Herons Arrive in Colorado?

Adult Great Blue Heron
Photo: mostbittern, CC BY 4.0 via iNaturalist

Great Blue Herons are in Colorado all year, but most are here in spring: numbers build from mid March, peak in late April (21% of checklists), and fall back by mid June. In the quietest week (the second week of February) they are still on about 5.1% of checklists.

When to look

Numbers buildMar 15-21mid March
PeakApr 22-30late April
Fall back byJun 15-21mid June
FewestFeb 8-14the second week of February

Best: late April. Here all year; numbers build from mid March and fall back by mid June. Peak: on about 21% of Colorado checklists.

  1. Januncommon
  2. Febuncommon
  3. Marpeak season
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Augpeak season
  9. Seppeak season
  10. Octcommon
  11. Novcommon
  12. Decuncommon

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

0%10%20%30%Jan 1-7: 5.8% of 32254 checklistsJan 8-14: 6.1% of 23278 checklistsJan 15-21: 6.5% of 22933 checklistsJan 22-31: 5.9% of 30856 checklistsFeb 1-7: 5.8% of 21464 checklistsFeb 8-14: 4.9% of 22910 checklistsFeb 15-21: 4.7% of 28739 checklistsFeb 22-28: 6.4% of 21833 checklistsMar 1-7: 7.3% of 23066 checklistsMar 8-14: 9.1% of 23783 checklistsMar 15-21: 12% of 24797 checklistsMar 22-31: 16% of 38439 checklistsApr 1-7: 19% of 31676 checklistsApr 8-14: 19% of 35092 checklistsApr 15-21: 21% of 36778 checklistsApr 22-30: 21% of 50885 checklistsMay 1-7: 21% of 44186 checklistsMay 8-14: 20% of 49011 checklistsMay 15-21: 20% of 40784 checklistsMay 22-31: 17% of 53073 checklistsJun 1-7: 16% of 32432 checklistsJun 8-14: 15% of 29978 checklistsJun 15-21: 13% of 29457 checklistsJun 22-30: 13% of 36072 checklistsJul 1-7: 13% of 28857 checklistsJul 8-14: 11% of 27224 checklistsJul 15-21: 12% of 27629 checklistsJul 22-31: 13% of 37318 checklistsAug 1-7: 14% of 25893 checklistsAug 8-14: 16% of 24870 checklistsAug 15-21: 17% of 24035 checklistsAug 22-31: 19% of 35691 checklistsSep 1-7: 18% of 27068 checklistsSep 8-14: 18% of 26709 checklistsSep 15-21: 16% of 26098 checklistsSep 22-30: 15% of 31550 checklistsOct 1-7: 13% of 24110 checklistsOct 8-14: 12% of 23352 checklistsOct 15-21: 11% of 21895 checklistsOct 22-31: 10% of 28319 checklistsNov 1-7: 8.8% of 21698 checklistsNov 8-14: 8.6% of 21061 checklistsNov 15-21: 7.9% of 19855 checklistsNov 22-30: 7.6% of 25798 checklistsDec 1-7: 7.1% of 18626 checklistsDec 8-14: 6.2% of 19004 checklistsDec 15-21: 6.7% of 23103 checklistsDec 22-31: 5.7% 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.

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Where in Colorado

Best counties

Share of checklists at the peak
  1. Washington CountyBest mid August · 43 checklists that week, 2,511 in all70%
  2. Sedgwick CountyBest mid September · 38 checklists that week, 1,168 in all61%
  3. Morgan CountyBest the second week of September · 123 checklists that week, 5,181 in all52%
  4. Adams CountyBest early September · 900 checklists that week, 44,639 in all48%
  5. Logan CountyBest mid September · 83 checklists that week, 4,117 in all47%
  6. Kiowa CountyBest mid July · 42 checklists that week, 3,854 in all46%

Best spots

Share of checklists at the peak
  1. Ward EnterprisesLarimer County, best late March · 20 checklists that week, 287 in all98%
  2. Robb-Colorado River State Park Colorado River Wildlife Area SectionMesa County, best late April · 22 checklists that week, 172 in all97%
  3. Ish ReservoirBoulder County, best late July · 20 checklists that week, 237 in all97%
  4. Timnath ReservoirLarimer County, best the second week of August · 106 checklists that week, 1,723 in all97%
  5. Old St. Louis Natural AreaLarimer County, best late April · 33 checklists that week, 934 in all96%

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

Best time of day

In Colorado, the Great Blue Heron is most often listed on checklists started between 6 and 8 am (16% of those checklists).

0%5%10%15%20%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: 17% of 71991 checklists7 am: 15% of 159189 checklists8 am: 15% of 177206 checklists9 am: 14% of 165269 checklists10 am: 12% of 141029 checklists11 am: 11% of 115283 checklists12 pm: 11% of 96068 checklists1 pm: 11% of 89512 checklists2 pm: 11% of 86319 checklists3 pm: 11% of 82496 checklists4 pm: 13% of 71648 checklists5 pm: 15% of 52445 checklists6 pm: 16% 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
January5.8%6.1%6.5%5.9%
February5.8%4.9%4.7%6.4%
March7.3%9.1%12%16%
April19%19%21%21%
May21%20%20%17%
June16%15%13%13%
July13%11%12%13%
August14%16%17%19%
September18%18%16%15%
October13%12%11%10%
November8.8%8.6%7.9%7.6%
December7.1%6.2%6.7%5.7%

Neighboring states

  • Wyoming: arrives the second week of March, 1 week earlier than Colorado
  • New Mexico: year-round, peaks mid November
  • Utah: year-round, peaks early September
  • Nebraska: arrives early March, 2 weeks earlier than Colorado

Common questions

When do Great Blue Herons arrive in Colorado?
Great Blue Herons are in Colorado all year, but most are here in spring: numbers build from mid March, peak in late April (21% of checklists), and fall back by mid June. In the quietest week (the second week of February) they are still on about 5.1% of checklists.
When do Great Blue Herons leave Colorado?
Great Blue Herons never fully leave Colorado: numbers fall back below half their usual rate by mid June, but some are still reported in every week, about 5.1% of checklists at the low.
When is the best time to see a Great Blue Heron in Colorado?
The Great Blue Heron is reported most often in late April, on about 21% of Colorado checklists.
Where in Colorado are Great Blue Herons seen most often?
By county, Washington County, Sedgwick County, and Morgan County have the highest peak reporting rates for the Great Blue Heron (counties with at least 200 checklists).