WhenToBird

Astur cooperii · Accipitridae

When Do Cooper's Hawks Arrive in Illinois?

Adult male Cooper's Hawk
Photo: Shirley Zundell, CC BY 4.0 via iNaturalist

Cooper's Hawks are in Illinois all year, but most are here in fall: numbers build from late August, peak in late September (14% of checklists), and fall back by early November. In the quietest week (the second week of June) they are still on about 3.6% of checklists.

When to look

Numbers buildAug 22-31late August
PeakSep 22-30late September
Fall back byNov 1-7early November
FewestJun 8-14the second week of June

Best: late September. Here all year; numbers build from late August and fall back by early November. Peak: on about 14% of Illinois checklists.

  1. Jancommon
  2. Febuncommon
  3. Marcommon
  4. Aprcommon
  5. Maycommon
  6. Jununcommon
  7. Juluncommon
  8. Augcommon
  9. Seppeak season
  10. Octpeak season
  11. Novcommon
  12. Deccommon

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

0%5%10%15%20%Jan 1-7: 5.8% of 29700 checklistsJan 8-14: 6.0% of 20189 checklistsJan 15-21: 5.8% of 19784 checklistsJan 22-31: 5.5% of 26641 checklistsFeb 1-7: 5.1% of 20478 checklistsFeb 8-14: 5.2% of 21967 checklistsFeb 15-21: 5.0% of 28735 checklistsFeb 22-28: 4.8% of 24223 checklistsMar 1-7: 5.3% of 26775 checklistsMar 8-14: 6.2% of 27579 checklistsMar 15-21: 6.7% of 27193 checklistsMar 22-31: 7.3% of 42278 checklistsApr 1-7: 7.7% of 34579 checklistsApr 8-14: 8.1% of 38290 checklistsApr 15-21: 8.4% of 39261 checklistsApr 22-30: 8.0% of 59584 checklistsMay 1-7: 8.0% of 60485 checklistsMay 8-14: 6.7% of 59647 checklistsMay 15-21: 6.1% of 43173 checklistsMay 22-31: 4.7% of 47913 checklistsJun 1-7: 3.5% of 31151 checklistsJun 8-14: 3.6% of 27692 checklistsJun 15-21: 3.7% of 23983 checklistsJun 22-30: 3.7% of 28448 checklistsJul 1-7: 3.7% of 21273 checklistsJul 8-14: 3.4% of 19284 checklistsJul 15-21: 3.9% of 17712 checklistsJul 22-31: 3.9% of 24500 checklistsAug 1-7: 5.0% of 18498 checklistsAug 8-14: 6.5% of 19331 checklistsAug 15-21: 7.3% of 19983 checklistsAug 22-31: 8.6% of 31892 checklistsSep 1-7: 11% of 26396 checklistsSep 8-14: 11% of 25011 checklistsSep 15-21: 13% of 23597 checklistsSep 22-30: 15% of 30638 checklistsOct 1-7: 14% of 23949 checklistsOct 8-14: 13% of 24412 checklistsOct 15-21: 13% of 22359 checklistsOct 22-31: 11% of 29794 checklistsNov 1-7: 9.1% of 21877 checklistsNov 8-14: 8.9% of 19742 checklistsNov 15-21: 8.3% of 18989 checklistsNov 22-30: 7.3% of 23905 checklistsDec 1-7: 7.3% of 16935 checklistsDec 8-14: 6.9% of 16687 checklistsDec 15-21: 6.6% of 20931 checklistsDec 22-31: 6.6% 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. Ford CountyBest the second week of December · 13 checklists that week, 762 in all26%
  2. Perry CountyBest the second week of December · 11 checklists that week, 783 in all22%
  3. DuPage CountyBest late September · 3189 checklists that week, 134,332 in all21%
  4. Grundy CountyBest late November · 90 checklists that week, 5,050 in all21%
  5. Lake CountyBest early October · 1814 checklists that week, 113,940 in all20%
  6. Cook CountyBest late September · 10568 checklists that week, 432,644 in all19%

Best spots

Share of checklists at the peak
  1. Sand Pond (Kellogg Creek)Lake County, best the second week of October · 25 checklists that week, 544 in all62%
  2. Burnham (Daniel)Cook County, best early October · 51 checklists that week, 1,106 in all52%
  3. Cantighy ParkDuPage County, best the second week of April · 20 checklists that week, 332 in all50%

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

Best time of day

In Illinois, the Cooper's Hawk is most often listed on checklists started between 6 and 8 am (10% of those checklists).

0%5%10%15%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: 9.6% of 95511 checklists7 am: 11% of 164584 checklists8 am: 9.4% of 163654 checklists9 am: 8.1% of 141804 checklists10 am: 6.7% of 122882 checklists11 am: 6.1% of 100640 checklists12 pm: 5.9% of 89894 checklists1 pm: 5.7% of 82729 checklists2 pm: 5.8% of 79801 checklists3 pm: 5.6% of 82169 checklists4 pm: 5.3% of 75124 checklists5 pm: 5.0% of 57708 checklists6 pm: 4.0% 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
January5.8%6.0%5.8%5.5%
February5.1%5.2%5.0%4.8%
March5.3%6.2%6.7%7.3%
April7.7%8.1%8.4%8.0%
May8.0%6.7%6.1%4.7%
June3.5%3.6%3.7%3.7%
July3.7%3.4%3.9%3.9%
August5.0%6.5%7.3%8.6%
September11%11%13%15%
October14%13%13%11%
November9.1%8.9%8.3%7.3%
December7.3%6.9%6.6%6.6%

Neighboring states

  • Indiana: arrives the second week of September, 2 weeks later than Illinois
  • Wisconsin: arrives late August, in the same week than Illinois
  • Michigan: arrives the second week of July, 6 weeks earlier than Illinois
  • Iowa: arrives mid June, 9 weeks earlier than Illinois

Common questions

When do Cooper's Hawks arrive in Illinois?
Cooper's Hawks are in Illinois all year, but most are here in fall: numbers build from late August, peak in late September (14% of checklists), and fall back by early November. In the quietest week (the second week of June) they are still on about 3.6% of checklists.
When do Cooper's Hawks leave Illinois?
Cooper's Hawks never fully leave Illinois: numbers fall back below half their usual rate by early November, but some are still reported in every week, about 3.6% of checklists at the low.
When is the best time to see a Cooper's Hawk in Illinois?
The Cooper's Hawk is reported most often in late September, on about 14% of Illinois checklists.
Where in Illinois are Cooper's Hawks seen most often?
By county, Ford County, Perry County, and DuPage County have the highest peak reporting rates for the Cooper's Hawk (counties with at least 200 checklists).