WhenToBird

Sterna forsteri · Laridae

When Do Forster's Terns Arrive in Wisconsin?

Adult Forster's Tern
Photo: Aitor, CC BY 4.0 via iNaturalist

Forster's Terns arrive in Wisconsin in mid April, peak in early May (2.9% of checklists), and most are gone by early August.

When to look

First arrivalsApr 15-21mid April
Common byApr 15-21mid April
PeakMay 1-7early May
Most gone byAug 1-7early August

Best: early May. First arrivals mid April; most are gone by early August. Peak: on about 2.9% 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. Auguncommon
  9. Seprare
  10. Octrare
  11. Novnot usually seen
  12. Decnot usually seen

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

0%1%2%3%4%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% of 40171 checklistsApr 1-7: 0.1% of 34961 checklistsApr 8-14: 0.2% of 39128 checklistsApr 15-21: 1.1% of 38887 checklistsApr 22-30: 2.5% of 57231 checklistsMay 1-7: 3.3% of 55115 checklistsMay 8-14: 2.8% of 63098 checklistsMay 15-21: 2.4% of 49821 checklistsMay 22-31: 2.1% of 56796 checklistsJun 1-7: 2.4% of 33621 checklistsJun 8-14: 1.7% of 31282 checklistsJun 15-21: 1.7% of 30186 checklistsJun 22-30: 1.2% of 35128 checklistsJul 1-7: 1.3% of 27088 checklistsJul 8-14: 1.2% of 23293 checklistsJul 15-21: 1.1% of 20933 checklistsJul 22-31: 0.9% of 27595 checklistsAug 1-7: 0.7% of 19147 checklistsAug 8-14: 0.6% of 18286 checklistsAug 15-21: 0.6% of 19195 checklistsAug 22-31: 0.4% of 28229 checklistsSep 1-7: 0.3% of 22408 checklistsSep 8-14: 0.3% of 20857 checklistsSep 15-21: 0.6% of 20707 checklistsSep 22-30: 0.4% of 26469 checklistsOct 1-7: 0.3% of 21069 checklistsOct 8-14: 0.2% of 21011 checklistsOct 15-21: 0.1% of 20006 checklistsOct 22-31: 0.1% of 26362 checklistsNov 1-7: 0.1% of 18928 checklistsNov 8-14: 0.1% 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.

Embed this map on your site

Where in Wisconsin

Best counties

Share of checklists at the peak
  1. Dodge CountyBest early June · 1223 checklists that week, 34,980 in all32%
  2. Marquette CountyBest the second week of May · 178 checklists that week, 3,706 in all23%
  3. Green Lake CountyBest early May · 737 checklists that week, 15,345 in all10%
  4. Brown CountyBest late June · 853 checklists that week, 36,306 in all9.1%
  5. Racine CountyBest the second week of May · 936 checklists that week, 18,400 in all8.7%
  6. Manitowoc CountyBest late May · 1357 checklists that week, 26,017 in all8.1%

Best spots

Share of checklists at the peak
  1. Horicon National Wildlife Refuge (Stony Island)Dodge County, best early June · 210 checklists that week, 1,653 in all83%
  2. Lake MariaGreen Lake County, best mid May · 21 checklists that week, 137 in all71%
  3. North Beach ParkRacine County, best the second week of May · 29 checklists that week, 490 in all66%
  4. Horicon National Wildlife Refuge (southeast)Dodge County, best mid May · 111 checklists that week, 2,074 in all61%
  5. Horicon National Wildlife Refuge (east)Dodge County, best mid May · 93 checklists that week, 1,923 in all61%
  6. South Side Memorial BeachSheboygan County, best late May · 30 checklists that week, 231 in all61%

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

Best time of day

In Wisconsin, the Forster's Tern is most often listed on checklists started between 5 and 7 pm (1.1% of those checklists).

0%0.5%1%1.5%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: 1.2% of 27016 checklists6 am: 1.1% of 83973 checklists7 am: 0.7% of 160717 checklists8 am: 0.8% of 160531 checklists9 am: 0.9% of 136968 checklists10 am: 1.0% of 119110 checklists11 am: 1.0% of 99116 checklists12 pm: 1.1% of 85078 checklists1 pm: 1.0% of 80688 checklists2 pm: 1.0% of 79140 checklists3 pm: 0.9% of 78599 checklists4 pm: 1.0% of 69767 checklists5 pm: 1.2% of 53229 checklists6 pm: 1.0% 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%
April0.1%0.2%1.1%2.5%
May3.3%2.8%2.4%2.1%
June2.4%1.7%1.7%1.2%
July1.3%1.2%1.1%0.9%
August0.7%0.6%0.6%0.4%
September0.3%0.3%0.6%0.4%
October0.3%0.2%0.1%0.1%
November0.1%0.1%0%0%
December0%0%0%0%

Neighboring states

  • Illinois: arrives mid April, in the same week than Wisconsin
  • Iowa: arrives mid April, in the same week than Wisconsin
  • Michigan: arrives the second week of April, 1 week earlier than Wisconsin
  • Minnesota: arrives mid April, in the same week than Wisconsin

Common questions

When do Forster's Terns arrive in Wisconsin?
Forster's Terns arrive in Wisconsin in mid April, peak in early May (2.9% of checklists), and most are gone by early August.
When do Forster's Terns leave Wisconsin?
Most Forster's Terns have left Wisconsin by early August, when reports fall below half their usual rate.
When is the best time to see a Forster's Tern in Wisconsin?
The Forster's Tern is reported most often in early May, on about 2.9% of Wisconsin checklists.
Where in Wisconsin are Forster's Terns seen most often?
By county, Dodge County, Marquette County, and Green Lake County have the highest peak reporting rates for the Forster's Tern (counties with at least 200 checklists).