WhenToBird

Tachycineta bicolor · Hirundinidae

When Do Tree Swallows Arrive in Pennsylvania?

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

Tree Swallows reach Pennsylvania in the second week of March, are common by late March, peak in late April (30% of checklists), and most are gone by mid August.

When to look

First arrivalsMar 8-14the second week of March
Common byMar 22-31late March
PeakApr 22-30late April
Most gone byAug 15-21mid August

Best: late April. First arrivals the second week of March; most are gone by mid August. Peak: on about 30% of Pennsylvania checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Sepuncommon
  10. Octuncommon
  11. Novrare
  12. Decnot usually seen

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

0%10%20%30%40%Jan 1-7: 0.1% of 47145 checklistsJan 8-14: 0.1% of 35840 checklistsJan 15-21: 0.1% of 35423 checklistsJan 22-31: 0.1% of 49126 checklistsFeb 1-7: 0.1% of 36366 checklistsFeb 8-14: 0.1% of 42248 checklistsFeb 15-21: 0.1% of 55888 checklistsFeb 22-28: 0.3% of 42050 checklistsMar 1-7: 1.1% of 42709 checklistsMar 8-14: 3.9% of 43985 checklistsMar 15-21: 7.7% of 44547 checklistsMar 22-31: 15% of 66940 checklistsApr 1-7: 22% of 51147 checklistsApr 8-14: 27% of 54868 checklistsApr 15-21: 29% of 57252 checklistsApr 22-30: 31% of 81727 checklistsMay 1-7: 30% of 76472 checklistsMay 8-14: 29% of 79341 checklistsMay 15-21: 30% of 61724 checklistsMay 22-31: 27% of 70722 checklistsJun 1-7: 25% of 45652 checklistsJun 8-14: 23% of 41810 checklistsJun 15-21: 23% of 38973 checklistsJun 22-30: 20% of 44255 checklistsJul 1-7: 16% of 34822 checklistsJul 8-14: 15% of 31104 checklistsJul 15-21: 12% of 29262 checklistsJul 22-31: 12% of 41436 checklistsAug 1-7: 11% of 29189 checklistsAug 8-14: 11% of 28840 checklistsAug 15-21: 10% of 29948 checklistsAug 22-31: 9.2% of 48235 checklistsSep 1-7: 7.9% of 37175 checklistsSep 8-14: 5.9% of 36527 checklistsSep 15-21: 5.4% of 37261 checklistsSep 22-30: 6.2% of 43583 checklistsOct 1-7: 6.6% of 35352 checklistsOct 8-14: 6.9% of 35560 checklistsOct 15-21: 7.2% of 33119 checklistsOct 22-31: 4.4% of 44654 checklistsNov 1-7: 1.2% of 32965 checklistsNov 8-14: 0.5% of 31305 checklistsNov 15-21: 0.1% of 29471 checklistsNov 22-30: 0.1% of 38642 checklistsDec 1-7: 0.1% of 28779 checklistsDec 8-14: 0.1% of 29486 checklistsDec 15-21: 0.1% of 37465 checklistsDec 22-31: 0.1% of 50651 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 Pennsylvania 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 Pennsylvania

Best counties

Share of checklists at the peak
  1. Juniata CountyBest the second week of June · 114 checklists that week, 9,807 in all48%
  2. Chester CountyBest late May · 4314 checklists that week, 144,121 in all45%
  3. Montour CountyBest the second week of May · 276 checklists that week, 6,082 in all45%
  4. Bucks CountyBest early May · 3120 checklists that week, 95,030 in all44%
  5. Susquehanna CountyBest early May · 736 checklists that week, 22,573 in all43%
  6. Carbon CountyBest mid April · 549 checklists that week, 16,269 in all41%

Best spots

Share of checklists at the peak
  1. Gwynedd Wildlife PreserveMontgomery County, best the second week of June · 39 checklists that week, 1,869 in all100%
  2. South Middleton Township ParkCumberland County, best early May · 23 checklists that week, 578 in all99%
  3. Dixon Meadow PreserveMontgomery County, best late May · 176 checklists that week, 6,425 in all98%
  4. State Game Land 046Lebanon County, best the second week of June · 23 checklists that week, 1,818 in all97%
  5. Houston PlaygroundPhiladelphia County, best early June · 39 checklists that week, 2,488 in all97%

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

Best time of day

In Pennsylvania, the Tree Swallow is most often listed on checklists started between 6 and 8 am (16% of those checklists).

0%5%10%15%20%12 am: too few checklists (1558) to judge1 am: too few checklists (1136) to judge2 am: too few checklists (839) to judge3 am: too few checklists (842) to judge4 am: too few checklists (2550) to judge5 am: too few checklists (18294) to judge6 am: 19% of 92903 checklists7 am: 14% of 241233 checklists8 am: 13% of 271994 checklists9 am: 13% of 236842 checklists10 am: 12% of 199508 checklists11 am: 11% of 161893 checklists12 pm: 10% of 143945 checklists1 pm: 9.9% of 134352 checklists2 pm: 9.5% of 129692 checklists3 pm: 9.3% of 126132 checklists4 pm: 10% of 115055 checklists5 pm: 13% of 90719 checklists6 pm: 16% of 67534 checklists7 pm: 15% of 43004 checklists8 pm: too few checklists (13966) to judge9 pm: too few checklists (3913) to judge10 pm: too few checklists (1989) to judge11 pm: too few checklists (1146) 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
January0.1%0.1%0.1%0.1%
February0.1%0.1%0.1%0.3%
March1.1%3.9%7.7%15%
April22%27%29%31%
May30%29%30%27%
June25%23%23%20%
July16%15%12%12%
August11%11%10%9.2%
September7.9%5.9%5.4%6.2%
October6.6%6.9%7.2%4.4%
November1.2%0.5%0.1%0.1%
December0.1%0.1%0.1%0.1%

Neighboring states

  • Maryland: arrives late February, 2 weeks earlier than Pennsylvania
  • District of Columbia: arrives early March, 1 week earlier than Pennsylvania
  • Delaware: arrives early March, 1 week earlier than Pennsylvania
  • New Jersey: arrives early March, 1 week earlier than Pennsylvania

Common questions

When do Tree Swallows arrive in Pennsylvania?
Tree Swallows reach Pennsylvania in the second week of March, are common by late March, peak in late April (30% of checklists), and most are gone by mid August.
When do Tree Swallows leave Pennsylvania?
Most Tree Swallows have left Pennsylvania by mid August, when reports fall below half their usual rate. Stragglers are still reported until early November.
When is the best time to see a Tree Swallow in Pennsylvania?
The Tree Swallow is reported most often in late April, on about 30% of Pennsylvania checklists.
Where in Pennsylvania are Tree Swallows seen most often?
By county, Juniata County, Chester County, and Montour County have the highest peak reporting rates for the Tree Swallow (counties with at least 200 checklists).