WhenToBird

Astur cooperii · Accipitridae

When Do Cooper's Hawks Arrive in Wisconsin?

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

Cooper's Hawks are in Wisconsin all year, but most are here in fall: numbers build from late August, peak in mid September (6.2% of checklists), and fall back by mid October. In the quietest week (the second week of June) they are still on about 2.0% of checklists.

When to look

Numbers buildAug 22-31late August
PeakSep 15-21mid September
Fall back byOct 15-21mid October
FewestJun 8-14the second week of June

Best: mid September. Here all year; numbers build from late August and fall back by mid October. Peak: on about 6.2% of Wisconsin checklists.

  1. Jancommon
  2. Febcommon
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Jununcommon
  7. Julcommon
  8. Augcommon
  9. Seppeak season
  10. Octpeak season
  11. Novcommon
  12. Deccommon

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

0%2%4%6%8%Jan 1-7: 3.4% of 27925 checklistsJan 8-14: 3.7% of 18337 checklistsJan 15-21: 3.8% of 17370 checklistsJan 22-31: 3.6% of 23777 checklistsFeb 1-7: 3.4% of 16656 checklistsFeb 8-14: 3.5% of 18286 checklistsFeb 15-21: 3.4% of 24739 checklistsFeb 22-28: 3.0% of 20113 checklistsMar 1-7: 3.0% of 24024 checklistsMar 8-14: 2.9% of 26722 checklistsMar 15-21: 3.3% of 27238 checklistsMar 22-31: 3.4% of 40171 checklistsApr 1-7: 4.0% of 34961 checklistsApr 8-14: 4.5% of 39128 checklistsApr 15-21: 4.7% of 38887 checklistsApr 22-30: 4.8% of 57231 checklistsMay 1-7: 5.2% of 55115 checklistsMay 8-14: 4.1% of 63098 checklistsMay 15-21: 3.3% of 49821 checklistsMay 22-31: 2.3% of 56796 checklistsJun 1-7: 1.9% of 33621 checklistsJun 8-14: 2.1% of 31282 checklistsJun 15-21: 2.0% of 30186 checklistsJun 22-30: 2.2% of 35128 checklistsJul 1-7: 2.3% of 27088 checklistsJul 8-14: 2.6% of 23293 checklistsJul 15-21: 2.7% of 20933 checklistsJul 22-31: 2.9% of 27595 checklistsAug 1-7: 3.3% of 19147 checklistsAug 8-14: 3.4% of 18286 checklistsAug 15-21: 3.7% of 19195 checklistsAug 22-31: 4.6% of 28229 checklistsSep 1-7: 5.2% of 22408 checklistsSep 8-14: 6.1% of 20857 checklistsSep 15-21: 6.0% of 20707 checklistsSep 22-30: 6.5% of 26469 checklistsOct 1-7: 6.0% of 21069 checklistsOct 8-14: 5.2% of 21011 checklistsOct 15-21: 4.7% of 20006 checklistsOct 22-31: 3.7% of 26362 checklistsNov 1-7: 3.9% of 18928 checklistsNov 8-14: 3.5% of 17052 checklistsNov 15-21: 3.6% of 16291 checklistsNov 22-30: 3.4% of 20564 checklistsDec 1-7: 3.7% of 15354 checklistsDec 8-14: 3.7% of 16294 checklistsDec 15-21: 4.2% of 21430 checklistsDec 22-31: 3.2% 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. Winnebago CountyBest late September · 476 checklists that week, 26,460 in all16%
  2. Milwaukee CountyBest late September · 2530 checklists that week, 114,667 in all16%
  3. Crawford CountyBest the second week of February · 62 checklists that week, 4,271 in all16%
  4. Ozaukee CountyBest the second week of October · 586 checklists that week, 38,294 in all11%
  5. Monroe CountyBest late September · 54 checklists that week, 3,836 in all11%
  6. Langlade CountyBest late January · 86 checklists that week, 5,023 in all10%

Best spots

Share of checklists at the peak
  1. Riverside ParkMilwaukee County, best early April · 24 checklists that week, 1,153 in all55%
  2. Uw ArboretumDane County, best mid September · 114 checklists that week, 7,732 in all44%
  3. Northeast Regional ParkRock County, best late July · 59 checklists that week, 105 in all41%
  4. Washington ParkMilwaukee County, best the second week of October · 20 checklists that week, 984 in all39%
  5. Havenwoods Forest Preserve and Nature CenterMilwaukee County, best the second week of October · 21 checklists that week, 1,148 in all38%

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

Best time of day

In Wisconsin, the Cooper's Hawk is most often listed on checklists started between 7 and 9 am (5.0% of those checklists).

0%2%4%6%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: 3.4% of 27016 checklists6 am: 4.8% of 83973 checklists7 am: 5.1% of 160717 checklists8 am: 5.0% of 160531 checklists9 am: 4.2% of 136968 checklists10 am: 3.5% of 119110 checklists11 am: 3.1% of 99116 checklists12 pm: 2.9% of 85078 checklists1 pm: 3.1% of 80688 checklists2 pm: 3.1% of 79140 checklists3 pm: 3.3% of 78599 checklists4 pm: 3.0% of 69767 checklists5 pm: 2.9% of 53229 checklists6 pm: 2.8% 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
January3.4%3.7%3.8%3.6%
February3.4%3.5%3.4%3.0%
March3.0%2.9%3.3%3.4%
April4.0%4.5%4.7%4.8%
May5.2%4.1%3.3%2.3%
June1.9%2.1%2.0%2.2%
July2.3%2.6%2.7%2.9%
August3.3%3.4%3.7%4.6%
September5.2%6.1%6.0%6.5%
October6.0%5.2%4.7%3.7%
November3.9%3.5%3.6%3.4%
December3.7%3.7%4.2%3.2%

Neighboring states

  • Illinois: arrives late August, in the same week than Wisconsin
  • Iowa: arrives mid June, 9 weeks earlier than Wisconsin
  • Michigan: arrives the second week of July, 6 weeks earlier than Wisconsin
  • Minnesota: arrives the second week of March, 22 weeks earlier than Wisconsin

Common questions

When do Cooper's Hawks arrive in Wisconsin?
Cooper's Hawks are in Wisconsin all year, but most are here in fall: numbers build from late August, peak in mid September (6.2% of checklists), and fall back by mid October. In the quietest week (the second week of June) they are still on about 2.0% of checklists.
When do Cooper's Hawks leave Wisconsin?
Cooper's Hawks never fully leave Wisconsin: numbers fall back below half their usual rate by mid October, but some are still reported in every week, about 2.0% of checklists at the low.
When is the best time to see a Cooper's Hawk in Wisconsin?
The Cooper's Hawk is reported most often in mid September, on about 6.2% of Wisconsin checklists.
Where in Wisconsin are Cooper's Hawks seen most often?
By county, Winnebago County, Milwaukee County, and Crawford County have the highest peak reporting rates for the Cooper's Hawk (counties with at least 200 checklists).