WhenToBird

Ardea herodias · Ardeidae

When Do Great Blue Herons Arrive in Wisconsin?

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

Great Blue Herons reach Wisconsin in the second week of March, are common by early April, peak in mid August (21% of checklists), and most are gone by late October.

When to look

First arrivalsMar 8-14the second week of March
Common byApr 1-7early April
PeakAug 15-21mid August
Most gone byOct 22-31late October

Best: mid August. First arrivals the second week of March; most are gone by late October. Peak: on about 21% of Wisconsin checklists.

  1. Janrare
  2. Febnot usually seen
  3. Maruncommon
  4. Aprcommon
  5. Maycommon
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octcommon
  11. Novuncommon
  12. Decrare

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

0%10%20%30%Jan 1-7: 0.9% of 27925 checklistsJan 8-14: 0.9% of 18337 checklistsJan 15-21: 0.8% of 17370 checklistsJan 22-31: 0.6% of 23777 checklistsFeb 1-7: 0.7% of 16656 checklistsFeb 8-14: 0.6% of 18286 checklistsFeb 15-21: 0.4% of 24739 checklistsFeb 22-28: 0.4% of 20113 checklistsMar 1-7: 0.5% of 24024 checklistsMar 8-14: 1.3% of 26722 checklistsMar 15-21: 3.2% of 27238 checklistsMar 22-31: 6.3% of 40171 checklistsApr 1-7: 8.2% of 34961 checklistsApr 8-14: 9.9% of 39128 checklistsApr 15-21: 11% of 38887 checklistsApr 22-30: 12% of 57231 checklistsMay 1-7: 14% of 55115 checklistsMay 8-14: 14% of 63098 checklistsMay 15-21: 14% of 49821 checklistsMay 22-31: 14% of 56796 checklistsJun 1-7: 13% of 33621 checklistsJun 8-14: 12% of 31282 checklistsJun 15-21: 11% of 30186 checklistsJun 22-30: 12% of 35128 checklistsJul 1-7: 13% of 27088 checklistsJul 8-14: 15% of 23293 checklistsJul 15-21: 17% of 20933 checklistsJul 22-31: 19% of 27595 checklistsAug 1-7: 20% of 19147 checklistsAug 8-14: 21% of 18286 checklistsAug 15-21: 22% of 19195 checklistsAug 22-31: 21% of 28229 checklistsSep 1-7: 20% of 22408 checklistsSep 8-14: 20% of 20857 checklistsSep 15-21: 19% of 20707 checklistsSep 22-30: 16% of 26469 checklistsOct 1-7: 14% of 21069 checklistsOct 8-14: 12% of 21011 checklistsOct 15-21: 8.8% of 20006 checklistsOct 22-31: 6.9% of 26362 checklistsNov 1-7: 5.2% of 18928 checklistsNov 8-14: 3.3% of 17052 checklistsNov 15-21: 2.4% of 16291 checklistsNov 22-30: 1.4% of 20564 checklistsDec 1-7: 0.7% of 15354 checklistsDec 8-14: 0.9% of 16294 checklistsDec 15-21: 1.2% of 21430 checklistsDec 22-31: 0.8% of 26314 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 Wisconsin 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 Wisconsin

Best counties

Share of checklists at the peak
  1. Dodge CountyBest the second week of August · 811 checklists that week, 34,980 in all50%
  2. Kewaunee CountyBest mid August · 156 checklists that week, 9,747 in all48%
  3. Trempealeau CountyBest the second week of September · 84 checklists that week, 6,201 in all47%
  4. Buffalo CountyBest the second week of September · 29 checklists that week, 3,020 in all43%
  5. Marquette CountyBest the second week of September · 66 checklists that week, 3,706 in all41%
  6. Lafayette CountyBest the second week of September · 27 checklists that week, 1,911 in all39%

Best spots

Share of checklists at the peak
  1. Vernon Wildlife Area (southwest)Waukesha County, best the second week of August · 49 checklists that week, 819 in all98%
  2. State Owned Islands - WdMarathon County, best early April · 34 checklists that week, 415 in all98%
  3. South Rice LakeMarathon County, best the second week of August · 20 checklists that week, 534 in all96%
  4. Lake WisconsinSauk County, best late August · 82 checklists that week, 1,455 in all96%
  5. Menasha ConservancyCalumet County, best early April · 34 checklists that week, 550 in all95%
  6. Indian LakeDane County, best the second week of August · 23 checklists that week, 1,211 in all93%

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

Best time of day

In Wisconsin, the Great Blue Heron is most often listed on checklists started between 5 and 7 am (15% of those checklists).

0%5%10%15%20%12 am: too few checklists (993) to judge1 am: too few checklists (844) to judge2 am: too few checklists (839) to judge3 am: too few checklists (1488) to judge4 am: too few checklists (5344) to judge5 am: 14% of 27016 checklists6 am: 15% of 83973 checklists7 am: 12% of 160717 checklists8 am: 11% of 160531 checklists9 am: 9.4% of 136968 checklists10 am: 8.8% of 119110 checklists11 am: 8.0% of 99116 checklists12 pm: 7.4% of 85078 checklists1 pm: 7.9% of 80688 checklists2 pm: 7.9% of 79140 checklists3 pm: 8.2% of 78599 checklists4 pm: 9.2% of 69767 checklists5 pm: 12% of 53229 checklists6 pm: 14% of 38769 checklists7 pm: too few checklists (24396) to judge8 pm: too few checklists (10155) to judge9 pm: too few checklists (4990) to judge10 pm: too few checklists (2463) to judge11 pm: too few checklists (1281) 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
January0.9%0.9%0.8%0.6%
February0.7%0.6%0.4%0.4%
March0.5%1.3%3.2%6.3%
April8.2%9.9%11%12%
May14%14%14%14%
June13%12%11%12%
July13%15%17%19%
August20%21%22%21%
September20%20%19%16%
October14%12%8.8%6.9%
November5.2%3.3%2.4%1.4%
December0.7%0.9%1.2%0.8%

Neighboring states

  • Illinois: arrives early April, 3 weeks later than Wisconsin
  • Iowa: arrives early March, 1 week earlier than Wisconsin
  • Michigan: arrives mid April, 5 weeks later than Wisconsin
  • Minnesota: arrives mid March, 1 week later than Wisconsin

Common questions

When do Great Blue Herons arrive in Wisconsin?
Great Blue Herons reach Wisconsin in the second week of March, are common by early April, peak in mid August (21% of checklists), and most are gone by late October.
When do Great Blue Herons leave Wisconsin?
Most Great Blue Herons have left Wisconsin by late October, when reports fall below half their usual rate. Stragglers are still reported until late November.
When is the best time to see a Great Blue Heron in Wisconsin?
The Great Blue Heron is reported most often in mid August, on about 21% of Wisconsin checklists.
Where in Wisconsin are Great Blue Herons seen most often?
By county, Dodge County, Kewaunee County, and Trempealeau County have the highest peak reporting rates for the Great Blue Heron (counties with at least 200 checklists).