WhenToBird

Hydroprogne caspia · Laridae

When Do Caspian Terns Arrive in Wisconsin?

Adult Caspian Tern
Photo: Daughter Dad, CC BY 4.0 via iNaturalist

Caspian Terns reach Wisconsin in the second week of April, are common by mid April, peak in early May (5.2% of checklists), and most are gone by early September.

When to look

First arrivalsApr 8-14the second week of April
Common byApr 15-21mid April
PeakMay 1-7early May
Most gone bySep 1-7early September

Best: early May. First arrivals the second week of April; most are gone by early September. Peak: on about 5.2% of Wisconsin checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Julcommon
  8. Augpeak season
  9. Sepcommon
  10. Octrare
  11. Novnot usually seen
  12. Decnot usually seen

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

0%2%4%6%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% of 26722 checklistsMar 15-21: 0% of 27238 checklistsMar 22-31: 0.1% of 40171 checklistsApr 1-7: 0.1% of 34961 checklistsApr 8-14: 0.9% of 39128 checklistsApr 15-21: 2.3% of 38887 checklistsApr 22-30: 5.1% of 57231 checklistsMay 1-7: 5.9% of 55115 checklistsMay 8-14: 4.6% of 63098 checklistsMay 15-21: 4.8% of 49821 checklistsMay 22-31: 3.5% of 56796 checklistsJun 1-7: 1.9% of 33621 checklistsJun 8-14: 1.5% of 31282 checklistsJun 15-21: 1.7% of 30186 checklistsJun 22-30: 1.7% of 35128 checklistsJul 1-7: 1.9% of 27088 checklistsJul 8-14: 2.5% of 23293 checklistsJul 15-21: 2.7% of 20933 checklistsJul 22-31: 3.9% of 27595 checklistsAug 1-7: 4.5% of 19147 checklistsAug 8-14: 3.8% of 18286 checklistsAug 15-21: 3.7% of 19195 checklistsAug 22-31: 2.7% of 28229 checklistsSep 1-7: 2.0% of 22408 checklistsSep 8-14: 1.4% of 20857 checklistsSep 15-21: 1.0% of 20707 checklistsSep 22-30: 0.4% of 26469 checklistsOct 1-7: 0.2% of 21069 checklistsOct 8-14: 0.1% of 21011 checklistsOct 15-21: 0.1% of 20006 checklistsOct 22-31: 0.1% of 26362 checklistsNov 1-7: 0% of 18928 checklistsNov 8-14: 0% of 17052 checklistsNov 15-21: 0% of 16291 checklistsNov 22-30: 0% of 20564 checklistsDec 1-7: 0% of 15354 checklistsDec 8-14: 0% 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. Kewaunee CountyBest early August · 137 checklists that week, 9,747 in all33%
  2. Racine CountyBest late April · 996 checklists that week, 18,400 in all31%
  3. Brown CountyBest late July · 850 checklists that week, 36,306 in all29%
  4. Manitowoc CountyBest early August · 340 checklists that week, 26,017 in all21%
  5. Marinette CountyBest the second week of May · 677 checklists that week, 16,075 in all20%
  6. Door CountyBest late July · 983 checklists that week, 37,397 in all18%

Best spots

Share of checklists at the peak
  1. North Beach ParkRacine County, best the second week of May · 29 checklists that week, 490 in all100%
  2. Pennoyer ParkKenosha County, best late April · 23 checklists that week, 129 in all94%
  3. Manitowoc Small Boat HarborManitowoc County, best early May · 75 checklists that week, 2,200 in all93%
  4. Dead Horse BayBrown County, best late April · 37 checklists that week, 630 in all88%
  5. Coal Dock ParkOzaukee County, best early May · 53 checklists that week, 1,961 in all83%

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

Best time of day

In Wisconsin, the Caspian Tern is most often listed on checklists started between 5 and 7 am (2.7% of those checklists).

0%1%2%3%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: 2.4% of 27016 checklists6 am: 2.9% of 83973 checklists7 am: 2.0% of 160717 checklists8 am: 1.7% of 160531 checklists9 am: 1.6% of 136968 checklists10 am: 1.6% of 119110 checklists11 am: 1.6% of 99116 checklists12 pm: 1.6% of 85078 checklists1 pm: 1.7% of 80688 checklists2 pm: 1.7% of 79140 checklists3 pm: 1.7% of 78599 checklists4 pm: 1.8% of 69767 checklists5 pm: 2.2% of 53229 checklists6 pm: 2.4% 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%0%0.1%
April0.1%0.9%2.3%5.1%
May5.9%4.6%4.8%3.5%
June1.9%1.5%1.7%1.7%
July1.9%2.5%2.7%3.9%
August4.5%3.8%3.7%2.7%
September2.0%1.4%1.0%0.4%
October0.2%0.1%0.1%0.1%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Illinois: arrives late March, 2 weeks earlier than Wisconsin
  • Iowa: arrives late July, 14 weeks later than Wisconsin
  • Michigan: arrives the second week of April, in the same week than Wisconsin
  • Minnesota: arrives late April, 2 weeks later than Wisconsin

Common questions

When do Caspian Terns arrive in Wisconsin?
Caspian Terns reach Wisconsin in the second week of April, are common by mid April, peak in early May (5.2% of checklists), and most are gone by early September.
When do Caspian Terns leave Wisconsin?
Most Caspian Terns have left Wisconsin by early September, when reports fall below half their usual rate. Stragglers are still reported until the second week of September.
When is the best time to see a Caspian Tern in Wisconsin?
The Caspian Tern is reported most often in early May, on about 5.2% of Wisconsin checklists.
Where in Wisconsin are Caspian Terns seen most often?
By county, Kewaunee County, Racine County, and Brown County have the highest peak reporting rates for the Caspian Tern (counties with at least 200 checklists).