WhenToBird

Circus hudsonius · Accipitridae

When Do Northern Harriers Arrive in Iowa?

Northern Harriers are winter birds in Iowa: the first arrive in early September, they are common by mid September, peak in the second week of October (5.1% of checklists), and most are gone by late April.

When to look

First arrivalsSep 1-7early September
Common bySep 15-21mid September
PeakOct 8-14the second week of October
Most gone byApr 22-30late April

Best: the second week of October. First arrivals early September; most are gone by late April. Peak: on about 5.1% of Iowa checklists.

  1. Jancommon
  2. Febcommon
  3. Marpeak season
  4. Aprpeak season
  5. Mayuncommon
  6. Junrare
  7. Julrare
  8. Auguncommon
  9. Sepcommon
  10. Octpeak season
  11. Novpeak season
  12. Deccommon

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

0%2%4%6%8%Jan 1-7: 3.2% of 5551 checklistsJan 8-14: 3.3% of 3498 checklistsJan 15-21: 2.1% of 3803 checklistsJan 22-31: 1.9% of 4807 checklistsFeb 1-7: 2.4% of 3613 checklistsFeb 8-14: 1.9% of 4173 checklistsFeb 15-21: 2.2% of 5796 checklistsFeb 22-28: 2.5% of 4394 checklistsMar 1-7: 3.1% of 5295 checklistsMar 8-14: 3.6% of 5679 checklistsMar 15-21: 4.1% of 5418 checklistsMar 22-31: 4.2% of 8613 checklistsApr 1-7: 5.2% of 6970 checklistsApr 8-14: 4.8% of 7511 checklistsApr 15-21: 4.4% of 8321 checklistsApr 22-30: 2.7% of 11976 checklistsMay 1-7: 1.1% of 11725 checklistsMay 8-14: 0.5% of 12626 checklistsMay 15-21: 0.3% of 9372 checklistsMay 22-31: 0.2% of 10330 checklistsJun 1-7: 0.1% of 5472 checklistsJun 8-14: 0.3% of 4568 checklistsJun 15-21: 0.2% of 3870 checklistsJun 22-30: 0.1% of 4780 checklistsJul 1-7: 0.2% of 4201 checklistsJul 8-14: 0% of 3605 checklistsJul 15-21: 0.2% of 3621 checklistsJul 22-31: 0.2% of 5093 checklistsAug 1-7: 0.3% of 3931 checklistsAug 8-14: 0.5% of 3488 checklistsAug 15-21: 0.7% of 3802 checklistsAug 22-31: 1.0% of 6293 checklistsSep 1-7: 1.1% of 5328 checklistsSep 8-14: 1.4% of 4622 checklistsSep 15-21: 2.2% of 4367 checklistsSep 22-30: 3.5% of 6086 checklistsOct 1-7: 4.2% of 4708 checklistsOct 8-14: 5.1% of 4791 checklistsOct 15-21: 6.1% of 4429 checklistsOct 22-31: 4.2% of 5633 checklistsNov 1-7: 3.8% of 4090 checklistsNov 8-14: 3.4% of 3416 checklistsNov 15-21: 2.9% of 3398 checklistsNov 22-30: 2.3% of 4679 checklistsDec 1-7: 3.4% of 3442 checklistsDec 8-14: 3.4% of 3322 checklistsDec 15-21: 3.8% of 4619 checklistsDec 22-31: 3.1% 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. Louisa CountyBest the second week of January · 11 checklists that week, 1,639 in all42%
  2. Ringgold CountyBest late March · 39 checklists that week, 1,141 in all37%
  3. Pocahontas CountyBest the second week of October · 10 checklists that week, 735 in all37%
  4. Sac CountyBest the second week of October · 15 checklists that week, 1,085 in all34%
  5. Union CountyBest the second week of January · 12 checklists that week, 1,133 in all28%
  6. Kossuth CountyBest the second week of September · 22 checklists that week, 628 in all28%

Best spots

Share of checklists at the peak
  1. Kellerton Bird Conservation Area Wildlife Management AreaRinggold County, best late March · 25 checklists that week, 227 in all53%
  2. Cedar River Crossing AdditionJohnson County, best mid October · 34 checklists that week, 564 in all48%
  3. Densmore LakeJackson County, best the second week of April · 22 checklists that week, 510 in all41%
  4. Dunbar Slough Wildlife Management AreaGreene County, best the second week of April · 21 checklists that week, 218 in all41%
  5. Little Storm Lake Wildlife Management AreaBuena Vista County, best the second week of April · 24 checklists that week, 968 in all40%

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

Best time of day

In Iowa, the Northern Harrier is most often listed on checklists started between 3 and 5 pm (3.1% of those checklists).

0%1%2%3%4%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: 1.3% of 11313 checklists7 am: 1.9% of 25717 checklists8 am: 2.1% of 29755 checklists9 am: 2.3% of 28897 checklists10 am: 2.3% of 26343 checklists11 am: 2.4% of 21210 checklists12 pm: 2.6% of 17662 checklists1 pm: 2.7% of 16595 checklists2 pm: 2.6% of 16405 checklists3 pm: 3.0% of 17030 checklists4 pm: 3.2% of 17378 checklists5 pm: 2.8% of 14251 checklists6 pm: 1.9% of 10349 checklists7 pm: 0.7% 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
January3.2%3.3%2.1%1.9%
February2.4%1.9%2.2%2.5%
March3.1%3.6%4.1%4.2%
April5.2%4.8%4.4%2.7%
May1.1%0.5%0.3%0.2%
June0.1%0.3%0.2%0.1%
July0.2%0%0.2%0.2%
August0.3%0.5%0.7%1.0%
September1.1%1.4%2.2%3.5%
October4.2%5.1%6.1%4.2%
November3.8%3.4%2.9%2.3%
December3.4%3.4%3.8%3.1%

Neighboring states

  • Missouri: arrives late September, 3 weeks later than Iowa
  • Wisconsin: arrives mid February, 22 weeks later than Iowa
  • Minnesota: arrives early March, 24 weeks earlier than Iowa
  • Illinois: arrives mid September, 2 weeks later than Iowa

Common questions

When do Northern Harriers arrive in Iowa?
Northern Harriers are winter birds in Iowa: the first arrive in early September, they are common by mid September, peak in the second week of October (5.1% of checklists), and most are gone by late April.
When do Northern Harriers leave Iowa?
Most Northern Harriers have left Iowa by late April, when reports fall below half their usual rate. Stragglers are still reported until early May.
When is the best time to see a Northern Harrier in Iowa?
The Northern Harrier is reported most often in the second week of October, on about 5.1% of Iowa checklists.
Where in Iowa are Northern Harriers seen most often?
By county, Louisa County, Ringgold County, and Pocahontas County have the highest peak reporting rates for the Northern Harrier (counties with at least 200 checklists).