WhenToBird

Circus hudsonius · Accipitridae

When Do Northern Harriers Arrive in Illinois?

Northern Harriers are winter birds in Illinois: the first arrive in mid September, they are common by early October, peak in the second week of January (4.6% of checklists), and most are gone by the second week of April.

When to look

First arrivalsSep 15-21mid September
Common byOct 1-7early October
PeakJan 8-14the second week of January
Most gone byApr 8-14the second week of April

Best: the second week of January. First arrivals mid September; most are gone by the second week of April. Peak: on about 4.6% of Illinois checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marcommon
  4. Aprcommon
  5. Mayrare
  6. Junnot usually seen
  7. Julrare
  8. Augrare
  9. Sepuncommon
  10. Octpeak season
  11. Novpeak season
  12. Decpeak season

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

0%2%4%6%Jan 1-7: 4.5% of 29700 checklistsJan 8-14: 4.7% of 20189 checklistsJan 15-21: 4.5% of 19784 checklistsJan 22-31: 4.2% of 26641 checklistsFeb 1-7: 4.1% of 20478 checklistsFeb 8-14: 3.0% of 21967 checklistsFeb 15-21: 2.9% of 28735 checklistsFeb 22-28: 3.4% of 24223 checklistsMar 1-7: 3.1% of 26775 checklistsMar 8-14: 2.6% of 27579 checklistsMar 15-21: 2.5% of 27193 checklistsMar 22-31: 2.4% of 42278 checklistsApr 1-7: 2.4% of 34579 checklistsApr 8-14: 2.1% of 38290 checklistsApr 15-21: 1.5% of 39261 checklistsApr 22-30: 1.0% of 59584 checklistsMay 1-7: 0.7% of 60485 checklistsMay 8-14: 0.3% of 59647 checklistsMay 15-21: 0.2% of 43173 checklistsMay 22-31: 0.2% of 47913 checklistsJun 1-7: 0.1% of 31151 checklistsJun 8-14: 0.2% of 27692 checklistsJun 15-21: 0.1% of 23983 checklistsJun 22-30: 0.1% of 28448 checklistsJul 1-7: 0.2% of 21273 checklistsJul 8-14: 0.1% of 19284 checklistsJul 15-21: 0.1% of 17712 checklistsJul 22-31: 0.2% of 24500 checklistsAug 1-7: 0.3% of 18498 checklistsAug 8-14: 0.4% of 19331 checklistsAug 15-21: 0.6% of 19983 checklistsAug 22-31: 0.6% of 31892 checklistsSep 1-7: 0.7% of 26396 checklistsSep 8-14: 0.7% of 25011 checklistsSep 15-21: 0.7% of 23597 checklistsSep 22-30: 1.6% of 30638 checklistsOct 1-7: 2.3% of 23949 checklistsOct 8-14: 2.6% of 24412 checklistsOct 15-21: 3.8% of 22359 checklistsOct 22-31: 3.6% of 29794 checklistsNov 1-7: 4.0% of 21877 checklistsNov 8-14: 3.7% of 19742 checklistsNov 15-21: 3.4% of 18989 checklistsNov 22-30: 3.2% of 23905 checklistsDec 1-7: 3.4% of 16935 checklistsDec 8-14: 3.2% of 16687 checklistsDec 15-21: 3.6% of 20931 checklistsDec 22-31: 3.9% of 29011 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 Illinois 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 Illinois

Best counties

Share of checklists at the peak
  1. Jasper CountyBest late February · 21 checklists that week, 1,292 in all59%
  2. Perry CountyBest mid January · 20 checklists that week, 783 in all59%
  3. Gallatin CountyBest late January · 14 checklists that week, 625 in all57%
  4. Wayne CountyBest the second week of December · 10 checklists that week, 394 in all52%
  5. Putnam CountyBest early December · 51 checklists that week, 3,333 in all45%
  6. Grundy CountyBest late January · 120 checklists that week, 5,050 in all39%

Best spots

Share of checklists at the peak
  1. Prairie Ridge-Jasper State Natural AreaJasper County, best mid March · 28 checklists that week, 405 in all86%
  2. South Greenbelt PreserveCook County, best early November · 22 checklists that week, 1,639 in all84%
  3. Goose Lake Prairie State Natural AreaGrundy County, best late January · 45 checklists that week, 1,288 in all84%
  4. Midewin OtherWill County, best early December · 23 checklists that week, 920 in all80%
  5. Orland Grassland Land and Water ReserveCook County, best mid February · 20 checklists that week, 1,587 in all78%
  6. Brunner Family Forest Preserve (Lake Marian)Kane County, best the second week of February · 28 checklists that week, 712 in all76%

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

Best time of day

In Illinois, the Northern Harrier is most often listed on checklists started between 2 and 4 pm (2.6% of those checklists).

0%1%2%3%12 am: too few checklists (484) to judge1 am: too few checklists (631) to judge2 am: too few checklists (485) to judge3 am: too few checklists (610) to judge4 am: too few checklists (2321) to judge5 am: too few checklists (23536) to judge6 am: 1.3% of 95511 checklists7 am: 1.7% of 164584 checklists8 am: 1.8% of 163654 checklists9 am: 2.0% of 141804 checklists10 am: 1.9% of 122882 checklists11 am: 2.1% of 100640 checklists12 pm: 2.0% of 89894 checklists1 pm: 2.3% of 82729 checklists2 pm: 2.5% of 79801 checklists3 pm: 2.8% of 82169 checklists4 pm: 2.4% of 75124 checklists5 pm: 1.1% of 57708 checklists6 pm: 0.5% of 41843 checklists7 pm: too few checklists (20943) to judge8 pm: too few checklists (6131) to judge9 pm: too few checklists (1677) to judge10 pm: too few checklists (843) to judge11 pm: too few checklists (448) 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
January4.5%4.7%4.5%4.2%
February4.1%3.0%2.9%3.4%
March3.1%2.6%2.5%2.4%
April2.4%2.1%1.5%1.0%
May0.7%0.3%0.2%0.2%
June0.1%0.2%0.1%0.1%
July0.2%0.1%0.1%0.2%
August0.3%0.4%0.6%0.6%
September0.7%0.7%0.7%1.6%
October2.3%2.6%3.8%3.6%
November4.0%3.7%3.4%3.2%
December3.4%3.2%3.6%3.9%

Neighboring states

  • Indiana: arrives late September, 1 week later than Illinois
  • Wisconsin: arrives mid February, 20 weeks later than Illinois
  • Michigan: arrives early August, 6 weeks earlier than Illinois
  • Iowa: arrives early September, 2 weeks earlier than Illinois

Common questions

When do Northern Harriers arrive in Illinois?
Northern Harriers are winter birds in Illinois: the first arrive in mid September, they are common by early October, peak in the second week of January (4.6% of checklists), and most are gone by the second week of April.
When do Northern Harriers leave Illinois?
Most Northern Harriers have left Illinois by the second week of April, when reports fall below half their usual rate. Stragglers are still reported until late April.
When is the best time to see a Northern Harrier in Illinois?
The Northern Harrier is reported most often in the second week of January, on about 4.6% of Illinois checklists.
Where in Illinois are Northern Harriers seen most often?
By county, Jasper County, Perry County, and Gallatin County have the highest peak reporting rates for the Northern Harrier (counties with at least 200 checklists).