WhenToBird

Tachycineta bicolor · Hirundinidae

When Do Tree Swallows Arrive in Wisconsin?

Adult Tree Swallow
Photo: Carter Dorscht, CC0 1.0 via iNaturalist

Tree Swallows reach Wisconsin in late March, are common by early April, peak in the second week of May (36% of checklists), and most are gone by mid August.

When to look

First arrivalsMar 22-31late March
Common byApr 1-7early April
PeakMay 8-14the second week of May
Most gone byAug 15-21mid August

Best: the second week of May. First arrivals late March; most are gone by mid August. Peak: on about 36% of Wisconsin checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Maruncommon
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Augcommon
  9. Sepuncommon
  10. Octrare
  11. Novnot usually seen
  12. Decnot usually seen

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

0%10%20%30%40%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: 0.1% of 24024 checklistsMar 8-14: 0.2% of 26722 checklistsMar 15-21: 0.9% of 27238 checklistsMar 22-31: 4.2% of 40171 checklistsApr 1-7: 13% of 34961 checklistsApr 8-14: 23% of 39128 checklistsApr 15-21: 26% of 38887 checklistsApr 22-30: 33% of 57231 checklistsMay 1-7: 37% of 55115 checklistsMay 8-14: 36% of 63098 checklistsMay 15-21: 35% of 49821 checklistsMay 22-31: 32% of 56796 checklistsJun 1-7: 29% of 33621 checklistsJun 8-14: 27% of 31282 checklistsJun 15-21: 25% of 30186 checklistsJun 22-30: 25% of 35128 checklistsJul 1-7: 22% of 27088 checklistsJul 8-14: 19% of 23293 checklistsJul 15-21: 17% of 20933 checklistsJul 22-31: 15% of 27595 checklistsAug 1-7: 13% of 19147 checklistsAug 8-14: 14% of 18286 checklistsAug 15-21: 13% of 19195 checklistsAug 22-31: 10% of 28229 checklistsSep 1-7: 8.9% of 22408 checklistsSep 8-14: 6.1% of 20857 checklistsSep 15-21: 3.0% of 20707 checklistsSep 22-30: 3.0% of 26469 checklistsOct 1-7: 3.4% of 21069 checklistsOct 8-14: 2.6% of 21011 checklistsOct 15-21: 1.5% of 20006 checklistsOct 22-31: 0.3% 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 all64%
  2. Taylor CountyBest the second week of May · 104 checklists that week, 4,326 in all60%
  3. Marquette CountyBest the second week of May · 178 checklists that week, 3,706 in all57%
  4. Calumet CountyBest the second week of May · 959 checklists that week, 12,359 in all56%
  5. Washburn CountyBest the second week of May · 355 checklists that week, 7,099 in all56%
  6. Green Lake CountyBest early May · 737 checklists that week, 15,345 in all51%

Best spots

Share of checklists at the peak
  1. Glacial Habitat Restoration - LmWinnebago County, best late May · 22 checklists that week, 269 in all100%
  2. Little Turtle FlowageIron County, best late May · 33 checklists that week, 283 in all100%
  3. Dartford Mill Pond (Green Lake 115)Green Lake County, best the second week of May · 23 checklists that week, 113 in all100%
  4. Vernon Wildlife Area (southwest)Waukesha County, best late May · 39 checklists that week, 819 in all99%
  5. Vern Wolf LakeKenosha County, best mid May · 20 checklists that week, 573 in all99%
  6. Lakeshore State ParkMilwaukee County, best mid June · 20 checklists that week, 2,503 in all98%

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

Best time of day

In Wisconsin, the Tree Swallow is most often listed on checklists started between 5 and 7 am (22% of those checklists).

0%10%20%30%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: 23% of 27016 checklists6 am: 21% of 83973 checklists7 am: 16% of 160717 checklists8 am: 15% of 160531 checklists9 am: 15% of 136968 checklists10 am: 14% of 119110 checklists11 am: 13% of 99116 checklists12 pm: 12% of 85078 checklists1 pm: 12% of 80688 checklists2 pm: 12% of 79140 checklists3 pm: 11% of 78599 checklists4 pm: 13% of 69767 checklists5 pm: 16% of 53229 checklists6 pm: 19% 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%
March0.1%0.2%0.9%4.2%
April13%23%26%33%
May37%36%35%32%
June29%27%25%25%
July22%19%17%15%
August13%14%13%10%
September8.9%6.1%3.0%3.0%
October3.4%2.6%1.5%0.3%
November0.1%0.1%0%0%
December0%0%0%0%

Neighboring states

  • Illinois: arrives the second week of March, 2 weeks earlier than Wisconsin
  • Iowa: arrives mid March, 1 week earlier than Wisconsin
  • Michigan: arrives mid March, 1 week earlier than Wisconsin
  • Minnesota: arrives early April, 1 week later than Wisconsin

Common questions

When do Tree Swallows arrive in Wisconsin?
Tree Swallows reach Wisconsin in late March, are common by early April, peak in the second week of May (36% of checklists), and most are gone by mid August.
When do Tree Swallows leave Wisconsin?
Most Tree Swallows have left Wisconsin by mid August, when reports fall below half their usual rate. Stragglers are still reported until the second week of October.
When is the best time to see a Tree Swallow in Wisconsin?
The Tree Swallow is reported most often in the second week of May, on about 36% of Wisconsin checklists.
Where in Wisconsin are Tree Swallows seen most often?
By county, Dodge County, Taylor County, and Marquette County have the highest peak reporting rates for the Tree Swallow (counties with at least 200 checklists).