WhenToBird

Ardea herodias · Ardeidae

When Do Great Blue Herons Arrive in Montana?

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

Great Blue Herons are in Montana all year, but most are here in summer: numbers build from early April, peak in mid August (13% of checklists), and fall back by late September. In the quietest week (mid February) they are still on about 3.2% of checklists.

When to look

Numbers buildApr 1-7early April
PeakAug 15-21mid August
Fall back bySep 22-30late September
FewestFeb 15-21mid February

Best: mid August. Here all year; numbers build from early April and fall back by late September. Peak: on about 13% of Montana checklists.

  1. Januncommon
  2. Febuncommon
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octcommon
  11. Novuncommon
  12. Decuncommon

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

0%5%10%15%Jan 1-7: 4.3% of 7987 checklistsJan 8-14: 4.2% of 5561 checklistsJan 15-21: 4.6% of 5613 checklistsJan 22-31: 4.2% of 7881 checklistsFeb 1-7: 3.9% of 5018 checklistsFeb 8-14: 3.4% of 5598 checklistsFeb 15-21: 2.8% of 7247 checklistsFeb 22-28: 3.5% of 5531 checklistsMar 1-7: 4.1% of 6110 checklistsMar 8-14: 4.5% of 6623 checklistsMar 15-21: 5.1% of 7687 checklistsMar 22-31: 7.8% of 11095 checklistsApr 1-7: 9.5% of 7774 checklistsApr 8-14: 11% of 8785 checklistsApr 15-21: 12% of 9684 checklistsApr 22-30: 12% of 13805 checklistsMay 1-7: 12% of 11847 checklistsMay 8-14: 12% of 13547 checklistsMay 15-21: 11% of 13019 checklistsMay 22-31: 10% of 20456 checklistsJun 1-7: 9.9% of 12993 checklistsJun 8-14: 9.7% of 11594 checklistsJun 15-21: 9.7% of 11159 checklistsJun 22-30: 9.3% of 13786 checklistsJul 1-7: 8.6% of 9584 checklistsJul 8-14: 8.3% of 9078 checklistsJul 15-21: 9.7% of 7905 checklistsJul 22-31: 11% of 10906 checklistsAug 1-7: 12% of 7335 checklistsAug 8-14: 13% of 6868 checklistsAug 15-21: 13% of 6866 checklistsAug 22-31: 13% of 10076 checklistsSep 1-7: 12% of 7670 checklistsSep 8-14: 11% of 7490 checklistsSep 15-21: 11% of 6804 checklistsSep 22-30: 9.1% of 8016 checklistsOct 1-7: 7.4% of 5996 checklistsOct 8-14: 5.6% of 6156 checklistsOct 15-21: 5.4% of 5742 checklistsOct 22-31: 4.4% of 7790 checklistsNov 1-7: 4.9% of 5353 checklistsNov 8-14: 4.8% of 5475 checklistsNov 15-21: 4.8% of 4603 checklistsNov 22-30: 4.1% of 6067 checklistsDec 1-7: 4.0% of 4362 checklistsDec 8-14: 5.2% of 4467 checklistsDec 15-21: 4.7% of 5328 checklistsDec 22-31: 4.0% of 6672 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 Montana 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 Montana

Best counties

Share of checklists at the peak
  1. Broadwater CountyBest late August · 114 checklists that week, 2,470 in all47%
  2. Fallon CountyBest the second week of August · 13 checklists that week, 542 in all44%
  3. Lake CountyBest early September · 314 checklists that week, 19,478 in all42%
  4. Teton CountyBest the second week of September · 59 checklists that week, 2,579 in all41%
  5. Deer Lodge CountyBest early May · 286 checklists that week, 8,732 in all35%
  6. Hill CountyBest mid August · 32 checklists that week, 988 in all34%

Best spots

Share of checklists at the peak
  1. Pablo ReservoirLake County, best mid August · 33 checklists that week, 791 in all95%
  2. Kicking Horse ReservoirLake County, best early September · 26 checklists that week, 661 in all94%
  3. Ninepipe ReservoirLake County, best the second week of September · 40 checklists that week, 1,128 in all90%
  4. Lake Helena Wildlife Management AreaLewis and Clark County, best mid August · 22 checklists that week, 1,103 in all89%
  5. Canyon Ferry Wildlife Management AreaBroadwater County, best early September · 30 checklists that week, 301 in all87%
  6. Lee Metcalf National Wildlife Refuge (northeast)Ravalli County, best late May · 32 checklists that week, 838 in all87%

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

Best time of day

In Montana, the Great Blue Heron is most often listed on checklists started between 6 and 8 am (11% of those checklists).

0%5%10%15%12 am: too few checklists (183) to judge1 am: too few checklists (169) to judge2 am: too few checklists (163) to judge3 am: too few checklists (212) to judge4 am: too few checklists (503) to judge5 am: too few checklists (4022) to judge6 am: 13% of 12719 checklists7 am: 11% of 31202 checklists8 am: 9.0% of 47646 checklists9 am: 9.0% of 44624 checklists10 am: 8.2% of 40704 checklists11 am: 7.6% of 33825 checklists12 pm: 7.0% of 29407 checklists1 pm: 7.1% of 27959 checklists2 pm: 6.8% of 26928 checklists3 pm: 7.5% of 25313 checklists4 pm: 7.7% of 22151 checklists5 pm: 9.2% of 16884 checklists6 pm: 11% of 13780 checklists7 pm: 9.8% of 9926 checklists8 pm: too few checklists (5765) to judge9 pm: too few checklists (2099) to judge10 pm: too few checklists (595) to judge11 pm: too few checklists (230) 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
January4.3%4.2%4.6%4.2%
February3.9%3.4%2.8%3.5%
March4.1%4.5%5.1%7.8%
April9.5%11%12%12%
May12%12%11%10%
June9.9%9.7%9.7%9.3%
July8.6%8.3%9.7%11%
August12%13%13%13%
September12%11%11%9.1%
October7.4%5.6%5.4%4.4%
November4.9%4.8%4.8%4.1%
December4.0%5.2%4.7%4.0%

Neighboring states

  • Idaho: year-round, peaks early September
  • Wyoming: arrives the second week of March, 3 weeks earlier than Montana
  • Utah: year-round, peaks early September
  • Washington: year-round, peaks early September

Common questions

When do Great Blue Herons arrive in Montana?
Great Blue Herons are in Montana all year, but most are here in summer: numbers build from early April, peak in mid August (13% of checklists), and fall back by late September. In the quietest week (mid February) they are still on about 3.2% of checklists.
When do Great Blue Herons leave Montana?
Great Blue Herons never fully leave Montana: numbers fall back below half their usual rate by late September, but some are still reported in every week, about 3.2% of checklists at the low.
When is the best time to see a Great Blue Heron in Montana?
The Great Blue Heron is reported most often in mid August, on about 13% of Montana checklists.
Where in Montana are Great Blue Herons seen most often?
By county, Broadwater County, Fallon County, and Lake County have the highest peak reporting rates for the Great Blue Heron (counties with at least 200 checklists).