WhenToBird

Pandion haliaetus · Pandionidae

When Do Ospreys Arrive in Wisconsin?

Adult female Osprey
Photo: Bill Levine, CC BY 4.0 via iNaturalist

Ospreys reach Wisconsin in late March, are common by early April, peak in mid August (6.4% of checklists), and most are gone by late September.

When to look

First arrivalsMar 22-31late March
Common byApr 1-7early April
PeakAug 15-21mid August
Most gone bySep 22-30late September

Best: mid August. First arrivals late March; most are gone by late September. Peak: on about 6.4% of Wisconsin checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Maruncommon
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octuncommon
  11. Novrare
  12. Decnot usually seen

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

0%2%4%6%8%Jan 1-7: 0% of 27925 checklistsJan 8-14: 0% of 18337 checklistsJan 15-21: 0% of 17370 checklistsJan 22-31: 0% of 23777 checklistsFeb 1-7: 0% of 16656 checklistsFeb 8-14: 0% of 18286 checklistsFeb 15-21: 0% of 24739 checklistsFeb 22-28: 0% of 20113 checklistsMar 1-7: 0% of 24024 checklistsMar 8-14: 0.1% of 26722 checklistsMar 15-21: 0.1% of 27238 checklistsMar 22-31: 0.6% of 40171 checklistsApr 1-7: 2.4% of 34961 checklistsApr 8-14: 4.4% of 39128 checklistsApr 15-21: 5.5% of 38887 checklistsApr 22-30: 5.9% of 57231 checklistsMay 1-7: 5.6% of 55115 checklistsMay 8-14: 4.6% of 63098 checklistsMay 15-21: 4.1% of 49821 checklistsMay 22-31: 3.8% of 56796 checklistsJun 1-7: 3.1% of 33621 checklistsJun 8-14: 2.9% of 31282 checklistsJun 15-21: 3.1% of 30186 checklistsJun 22-30: 3.0% of 35128 checklistsJul 1-7: 3.9% of 27088 checklistsJul 8-14: 4.2% of 23293 checklistsJul 15-21: 4.7% of 20933 checklistsJul 22-31: 5.0% of 27595 checklistsAug 1-7: 6.0% of 19147 checklistsAug 8-14: 6.1% of 18286 checklistsAug 15-21: 6.3% of 19195 checklistsAug 22-31: 6.6% of 28229 checklistsSep 1-7: 5.4% of 22408 checklistsSep 8-14: 3.9% of 20857 checklistsSep 15-21: 3.4% of 20707 checklistsSep 22-30: 2.0% of 26469 checklistsOct 1-7: 1.0% of 21069 checklistsOct 8-14: 0.8% of 21011 checklistsOct 15-21: 0.5% of 20006 checklistsOct 22-31: 0.4% of 26362 checklistsNov 1-7: 0.3% of 18928 checklistsNov 8-14: 0.1% of 17052 checklistsNov 15-21: 0.1% of 16291 checklistsNov 22-30: 0.1% of 20564 checklistsDec 1-7: 0% of 15354 checklistsDec 8-14: 0.1% of 16294 checklistsDec 15-21: 0% of 21430 checklistsDec 22-31: 0% 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 mid August · 378 checklists that week, 26,460 in all28%
  2. Calumet CountyBest early May · 797 checklists that week, 12,359 in all23%
  3. Marquette CountyBest the second week of August · 55 checklists that week, 3,706 in all22%
  4. Kewaunee CountyBest early August · 137 checklists that week, 9,747 in all22%
  5. Barron CountyBest late August · 116 checklists that week, 6,745 in all21%
  6. Manitowoc CountyBest late July · 425 checklists that week, 26,017 in all20%

Best spots

Share of checklists at the peak
  1. West Twin River County ParkManitowoc County, best late April · 26 checklists that week, 240 in all92%
  2. Columbia County Waterfowl Production AreaColumbia County, best mid April · 24 checklists that week, 354 in all80%
  3. Little Turtle FlowageIron County, best late May · 33 checklists that week, 283 in all79%
  4. Lake Kegonsa State ParkDane County, best late April · 154 checklists that week, 3,030 in all75%
  5. Lulu LakeWalworth County, best early May · 33 checklists that week, 348 in all74%

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

Best time of day

In Wisconsin, the Osprey is most often listed on checklists started between 5 and 7 pm (3.6% 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: 2.9% of 27016 checklists6 am: 3.7% of 83973 checklists7 am: 2.9% of 160717 checklists8 am: 2.9% of 160531 checklists9 am: 2.8% of 136968 checklists10 am: 2.5% of 119110 checklists11 am: 2.2% of 99116 checklists12 pm: 2.1% of 85078 checklists1 pm: 2.2% of 80688 checklists2 pm: 2.4% of 79140 checklists3 pm: 2.5% of 78599 checklists4 pm: 3.0% of 69767 checklists5 pm: 3.5% of 53229 checklists6 pm: 3.8% 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
January0%0%0%0%
February0%0%0%0%
March0%0.1%0.1%0.6%
April2.4%4.4%5.5%5.9%
May5.6%4.6%4.1%3.8%
June3.1%2.9%3.1%3.0%
July3.9%4.2%4.7%5.0%
August6.0%6.1%6.3%6.6%
September5.4%3.9%3.4%2.0%
October1.0%0.8%0.5%0.4%
November0.3%0.1%0.1%0.1%
December0%0.1%0%0%

Neighboring states

  • Illinois: arrives late March, in the same week than Wisconsin
  • Iowa: arrives late March, in the same week than Wisconsin
  • Michigan: arrives late March, in the same week than Wisconsin
  • Minnesota: arrives early April, 1 week later than Wisconsin

Common questions

When do Ospreys arrive in Wisconsin?
Ospreys reach Wisconsin in late March, are common by early April, peak in mid August (6.4% of checklists), and most are gone by late September.
When do Ospreys leave Wisconsin?
Most Ospreys have left Wisconsin by late September, when reports fall below half their usual rate. Stragglers are still reported until early October.
When is the best time to see a Osprey in Wisconsin?
The Osprey is reported most often in mid August, on about 6.4% of Wisconsin checklists.
Where in Wisconsin are Ospreys seen most often?
By county, Winnebago County, Calumet County, and Marquette County have the highest peak reporting rates for the Osprey (counties with at least 200 checklists).