WhenToBird

Butorides virescens · Ardeidae

When Do Green Herons Arrive in Iowa?

Adult male Green Heron
Photo: Jonathan Eisen, CC BY 4.0 via iNaturalist

Green Herons arrive in Iowa in late April, peak in mid August (6.6% of checklists), and most are gone by late September.

When to look

First arrivalsApr 22-30late April
Common byApr 22-30late April
PeakAug 15-21mid August
Most gone bySep 22-30late September

Best: mid August. First arrivals late April; most are gone by late September. Peak: on about 6.6% of Iowa checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Apruncommon
  5. Maycommon
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octrare
  11. Novnot usually seen
  12. Decnot usually seen

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

0%2%4%6%8%Jan 1-7: 0% of 5551 checklistsJan 8-14: 0% of 3498 checklistsJan 15-21: 0% of 3803 checklistsJan 22-31: 0% of 4807 checklistsFeb 1-7: 0% of 3613 checklistsFeb 8-14: 0% of 4173 checklistsFeb 15-21: 0% of 5796 checklistsFeb 22-28: 0% of 4394 checklistsMar 1-7: 0% of 5295 checklistsMar 8-14: 0% of 5679 checklistsMar 15-21: 0% of 5418 checklistsMar 22-31: 0% of 8613 checklistsApr 1-7: 0% of 6970 checklistsApr 8-14: 0.1% of 7511 checklistsApr 15-21: 0.5% of 8321 checklistsApr 22-30: 1.9% of 11976 checklistsMay 1-7: 3.2% of 11725 checklistsMay 8-14: 3.3% of 12626 checklistsMay 15-21: 3.6% of 9372 checklistsMay 22-31: 3.4% of 10330 checklistsJun 1-7: 2.9% of 5472 checklistsJun 8-14: 3.2% of 4568 checklistsJun 15-21: 2.9% of 3870 checklistsJun 22-30: 3.3% of 4780 checklistsJul 1-7: 4.1% of 4201 checklistsJul 8-14: 4.7% of 3605 checklistsJul 15-21: 4.8% of 3621 checklistsJul 22-31: 5.2% of 5093 checklistsAug 1-7: 6.0% of 3931 checklistsAug 8-14: 6.9% of 3488 checklistsAug 15-21: 6.5% of 3802 checklistsAug 22-31: 6.4% of 6293 checklistsSep 1-7: 5.1% of 5328 checklistsSep 8-14: 3.9% of 4622 checklistsSep 15-21: 3.4% of 4367 checklistsSep 22-30: 1.7% of 6086 checklistsOct 1-7: 0.6% of 4708 checklistsOct 8-14: 0.2% of 4791 checklistsOct 15-21: 0.1% of 4429 checklistsOct 22-31: 0.1% of 5633 checklistsNov 1-7: 0.1% of 4090 checklistsNov 8-14: 0% of 3416 checklistsNov 15-21: 0% of 3398 checklistsNov 22-30: 0% of 4679 checklistsDec 1-7: 0% of 3442 checklistsDec 8-14: 0% of 3322 checklistsDec 15-21: 0% of 4619 checklistsDec 22-31: 0% of 5113 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 Iowa 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 Iowa

Best counties

Share of checklists at the peak
  1. Mahaska CountyBest the second week of September · 14 checklists that week, 912 in all38%
  2. Shelby CountyBest the second week of July · 10 checklists that week, 354 in all35%
  3. Clarke CountyBest late August · 15 checklists that week, 459 in all27%
  4. Louisa CountyBest the second week of August · 14 checklists that week, 1,639 in all20%
  5. Cerro Gordo CountyBest the second week of August · 21 checklists that week, 1,853 in all19%
  6. Mitchell CountyBest the second week of August · 12 checklists that week, 660 in all19%

Best spots

Share of checklists at the peak
  1. Ada Hayden Heritage ParkStory County, best mid July · 24 checklists that week, 1,681 in all55%
  2. Maskunky MarshMahaska County, best late August · 21 checklists that week, 487 in all49%
  3. John Deere MarshDubuque County, best late August · 35 checklists that week, 1,952 in all48%
  4. Lake Macbride State Park (southeast)Johnson County, best early August · 39 checklists that week, 275 in all48%
  5. Water Plant ParkJohnson County, best late August · 25 checklists that week, 1,004 in all44%
  6. Little Storm Lake Wildlife Management AreaBuena Vista County, best late August · 23 checklists that week, 968 in all42%

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

Best time of day

In Iowa, the Green Heron is most often listed on checklists started between 6 and 8 am (3.2% of those checklists).

0%2%4%6%12 am: too few checklists (96) to judge1 am: too few checklists (99) to judge2 am: too few checklists (67) to judge3 am: too few checklists (82) to judge4 am: too few checklists (201) to judge5 am: too few checklists (1888) to judge6 am: 4.7% of 11313 checklists7 am: 2.6% of 25717 checklists8 am: 2.3% of 29755 checklists9 am: 1.7% of 28897 checklists10 am: 1.3% of 26343 checklists11 am: 1.3% of 21210 checklists12 pm: 1.1% of 17662 checklists1 pm: 1.0% of 16595 checklists2 pm: 1.1% of 16405 checklists3 pm: 1.2% of 17030 checklists4 pm: 1.3% of 17378 checklists5 pm: 2.2% of 14251 checklists6 pm: 3.1% of 10349 checklists7 pm: 3.4% of 6233 checklists8 pm: too few checklists (2002) to judge9 pm: too few checklists (392) to judge10 pm: too few checklists (186) to judge11 pm: too few checklists (87) 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%0%0%0%
February0%0%0%0%
March0%0%0%0%
April0%0.1%0.5%1.9%
May3.2%3.3%3.6%3.4%
June2.9%3.2%2.9%3.3%
July4.1%4.7%4.8%5.2%
August6.0%6.9%6.5%6.4%
September5.1%3.9%3.4%1.7%
October0.6%0.2%0.1%0.1%
November0.1%0%0%0%
December0%0%0%0%

Neighboring states

  • Missouri: arrives mid April, 1 week earlier than Iowa
  • Wisconsin: arrives mid April, 1 week earlier than Iowa
  • Minnesota: arrives late April, in the same week than Iowa
  • Illinois: arrives mid April, 1 week earlier than Iowa

Common questions

When do Green Herons arrive in Iowa?
Green Herons arrive in Iowa in late April, peak in mid August (6.6% of checklists), and most are gone by late September.
When do Green Herons leave Iowa?
Most Green Herons have left Iowa by late September, when reports fall below half their usual rate.
When is the best time to see a Green Heron in Iowa?
The Green Heron is reported most often in mid August, on about 6.6% of Iowa checklists.
Where in Iowa are Green Herons seen most often?
By county, Mahaska County, Shelby County, and Clarke County have the highest peak reporting rates for the Green Heron (counties with at least 200 checklists).