WhenToBird

Circus hudsonius · Accipitridae

When Do Northern Harriers Arrive in Wisconsin?

Northern Harriers reach Wisconsin in mid February, are common by late February, peak in the second week of April (4.3% of checklists), and most are gone by mid May.

When to look

First arrivalsFeb 15-21mid February
Common byFeb 22-28late February
PeakApr 8-14the second week of April
Most gone byMay 15-21mid May

Best: the second week of April. First arrivals mid February; most are gone by mid May. Peak: on about 4.3% of Wisconsin checklists.

  1. Jancommon
  2. Febcommon
  3. Marpeak season
  4. Aprpeak season
  5. Maycommon
  6. Jununcommon
  7. Juluncommon
  8. Augcommon
  9. Sepcommon
  10. Octpeak season
  11. Novcommon
  12. Deccommon

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

0%2%4%6%Jan 1-7: 2.4% of 27925 checklistsJan 8-14: 2.0% of 18337 checklistsJan 15-21: 1.6% of 17370 checklistsJan 22-31: 1.6% of 23777 checklistsFeb 1-7: 1.3% of 16656 checklistsFeb 8-14: 1.4% of 18286 checklistsFeb 15-21: 1.2% of 24739 checklistsFeb 22-28: 1.8% of 20113 checklistsMar 1-7: 2.4% of 24024 checklistsMar 8-14: 2.8% of 26722 checklistsMar 15-21: 3.2% of 27238 checklistsMar 22-31: 3.5% of 40171 checklistsApr 1-7: 4.1% of 34961 checklistsApr 8-14: 4.4% of 39128 checklistsApr 15-21: 4.2% of 38887 checklistsApr 22-30: 3.5% of 57231 checklistsMay 1-7: 2.5% of 55115 checklistsMay 8-14: 1.8% of 63098 checklistsMay 15-21: 1.7% of 49821 checklistsMay 22-31: 1.6% of 56796 checklistsJun 1-7: 1.5% of 33621 checklistsJun 8-14: 1.4% of 31282 checklistsJun 15-21: 1.2% of 30186 checklistsJun 22-30: 1.4% of 35128 checklistsJul 1-7: 1.5% of 27088 checklistsJul 8-14: 1.5% of 23293 checklistsJul 15-21: 1.4% of 20933 checklistsJul 22-31: 1.7% of 27595 checklistsAug 1-7: 1.9% of 19147 checklistsAug 8-14: 3.2% of 18286 checklistsAug 15-21: 3.5% of 19195 checklistsAug 22-31: 2.7% of 28229 checklistsSep 1-7: 1.9% of 22408 checklistsSep 8-14: 2.0% of 20857 checklistsSep 15-21: 2.5% of 20707 checklistsSep 22-30: 2.9% of 26469 checklistsOct 1-7: 3.2% of 21069 checklistsOct 8-14: 3.4% of 21011 checklistsOct 15-21: 3.3% of 20006 checklistsOct 22-31: 3.0% of 26362 checklistsNov 1-7: 2.9% of 18928 checklistsNov 8-14: 2.5% of 17052 checklistsNov 15-21: 2.2% of 16291 checklistsNov 22-30: 1.9% of 20564 checklistsDec 1-7: 1.7% of 15354 checklistsDec 8-14: 1.8% of 16294 checklistsDec 15-21: 2.1% of 21430 checklistsDec 22-31: 1.8% 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. Burnett CountyBest the second week of October · 114 checklists that week, 11,034 in all26%
  2. Dodge CountyBest early November · 418 checklists that week, 34,980 in all23%
  3. Calumet CountyBest the second week of November · 143 checklists that week, 12,359 in all20%
  4. Columbia CountyBest the second week of October · 211 checklists that week, 15,761 in all19%
  5. Adams CountyBest early April · 157 checklists that week, 5,946 in all18%
  6. Clark CountyBest the second week of November · 10 checklists that week, 2,369 in all16%

Best spots

Share of checklists at the peak
  1. Paradise Valley Wildlife AreaWaukesha County, best the second week of November · 23 checklists that week, 848 in all74%
  2. Powell Marsh Wildlife AreaVilas County, best late August · 20 checklists that week, 480 in all70%
  3. Buena Vista Wildlife Area (northeast)Portage County, best late April · 28 checklists that week, 486 in all66%
  4. Killsnake Wildlife AreaCalumet County, best early November · 24 checklists that week, 572 in all63%

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

Best time of day

In Wisconsin, the Northern Harrier is most often listed on checklists started between 3 and 5 pm (3.2% of those checklists).

0%1%2%3%4%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: 2.3% of 27016 checklists6 am: 2.1% of 83973 checklists7 am: 2.0% of 160717 checklists8 am: 2.2% of 160531 checklists9 am: 2.4% of 136968 checklists10 am: 2.4% of 119110 checklists11 am: 2.4% of 99116 checklists12 pm: 2.3% of 85078 checklists1 pm: 2.6% of 80688 checklists2 pm: 2.8% of 79140 checklists3 pm: 3.1% of 78599 checklists4 pm: 3.3% of 69767 checklists5 pm: 2.6% of 53229 checklists6 pm: 2.1% 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
January2.4%2.0%1.6%1.6%
February1.3%1.4%1.2%1.8%
March2.4%2.8%3.2%3.5%
April4.1%4.4%4.2%3.5%
May2.5%1.8%1.7%1.6%
June1.5%1.4%1.2%1.4%
July1.5%1.5%1.4%1.7%
August1.9%3.2%3.5%2.7%
September1.9%2.0%2.5%2.9%
October3.2%3.4%3.3%3.0%
November2.9%2.5%2.2%1.9%
December1.7%1.8%2.1%1.8%

Neighboring states

  • Illinois: arrives mid September, 20 weeks earlier than Wisconsin
  • Iowa: arrives early September, 22 weeks earlier than Wisconsin
  • Michigan: arrives early August, 22 weeks later than Wisconsin
  • Minnesota: arrives early March, 2 weeks later than Wisconsin

Common questions

When do Northern Harriers arrive in Wisconsin?
Northern Harriers reach Wisconsin in mid February, are common by late February, peak in the second week of April (4.3% of checklists), and most are gone by mid May.
When do Northern Harriers leave Wisconsin?
Most Northern Harriers have left Wisconsin by mid May, when reports fall below half their usual rate. Stragglers are still reported until the second week of June.
When is the best time to see a Northern Harrier in Wisconsin?
The Northern Harrier is reported most often in the second week of April, on about 4.3% of Wisconsin checklists.
Where in Wisconsin are Northern Harriers seen most often?
By county, Burnett County, Dodge County, and Calumet County have the highest peak reporting rates for the Northern Harrier (counties with at least 200 checklists).