WhenToBird

Vireo philadelphicus · Vireonidae

When Do Philadelphia Vireos Arrive in Pennsylvania?

Adult Philadelphia Vireo
Photo: Sue Carnahan, CC BY 4.0 via iNaturalist

Philadelphia Vireos mostly pass through Pennsylvania: they arrive in early September, peak in mid September (2.1% of checklists), and most are gone by early October.

When to look

First arrivalsSep 1-7early September
Common bySep 1-7early September
PeakSep 15-21mid September
Most gone byOct 1-7early October

Best: mid September. First arrivals early September; most are gone by early October. Peak: on about 2.1% of Pennsylvania checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprnot usually seen
  5. Mayrare
  6. Junnot usually seen
  7. Julnot usually seen
  8. Auguncommon
  9. Seppeak season
  10. Octuncommon
  11. Novnot usually seen
  12. Decnot usually seen

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

0%1%2%3%Jan 1-7: 0% of 47145 checklistsJan 8-14: 0% of 35840 checklistsJan 15-21: 0% of 35423 checklistsJan 22-31: 0% of 49126 checklistsFeb 1-7: 0% of 36366 checklistsFeb 8-14: 0% of 42248 checklistsFeb 15-21: 0% of 55888 checklistsFeb 22-28: 0% of 42050 checklistsMar 1-7: 0% of 42709 checklistsMar 8-14: 0% of 43985 checklistsMar 15-21: 0% of 44547 checklistsMar 22-31: 0% of 66940 checklistsApr 1-7: 0% of 51147 checklistsApr 8-14: 0% of 54868 checklistsApr 15-21: 0% of 57252 checklistsApr 22-30: 0% of 81727 checklistsMay 1-7: 0.1% of 76472 checklistsMay 8-14: 0.2% of 79341 checklistsMay 15-21: 0.5% of 61724 checklistsMay 22-31: 0.1% of 70722 checklistsJun 1-7: 0.1% of 45652 checklistsJun 8-14: 0.1% of 41810 checklistsJun 15-21: 0% of 38973 checklistsJun 22-30: 0% of 44255 checklistsJul 1-7: 0% of 34822 checklistsJul 8-14: 0% of 31104 checklistsJul 15-21: 0% of 29262 checklistsJul 22-31: 0% of 41436 checklistsAug 1-7: 0% of 29189 checklistsAug 8-14: 0.1% of 28840 checklistsAug 15-21: 0.1% of 29948 checklistsAug 22-31: 0.2% of 48235 checklistsSep 1-7: 1.1% of 37175 checklistsSep 8-14: 2.1% of 36527 checklistsSep 15-21: 2.7% of 37261 checklistsSep 22-30: 1.7% of 43583 checklistsOct 1-7: 0.5% of 35352 checklistsOct 8-14: 0.1% of 35560 checklistsOct 15-21: 0.1% of 33119 checklistsOct 22-31: 0% of 44654 checklistsNov 1-7: 0% of 32965 checklistsNov 8-14: 0% of 31305 checklistsNov 15-21: 0% of 29471 checklistsNov 22-30: 0% of 38642 checklistsDec 1-7: 0% of 28779 checklistsDec 8-14: 0% of 29486 checklistsDec 15-21: 0% of 37465 checklistsDec 22-31: 0% 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. Montour CountyBest the second week of September · 104 checklists that week, 6,082 in all7.1%
  2. Wayne CountyBest the second week of September · 121 checklists that week, 10,444 in all6.4%
  3. Indiana CountyBest mid September · 312 checklists that week, 20,768 in all5.0%
  4. Schuylkill CountyBest the second week of September · 409 checklists that week, 22,261 in all4.8%
  5. Clarion CountyBest mid September · 131 checklists that week, 9,153 in all4.7%
  6. Allegheny CountyBest mid September · 2901 checklists that week, 152,989 in all4.4%

Best spots

Share of checklists at the peak
  1. Blue Spruce ParkIndiana County, best mid September · 35 checklists that week, 667 in all33%
  2. Deer Lakes ParkAllegheny County, best late September · 22 checklists that week, 725 in all29%
  3. Woodcock Creek LakeCrawford County, best mid September · 29 checklists that week, 389 in all24%
  4. Schuylkill Rowing Basin (Lemon Hill)Philadelphia County, best the second week of September · 21 checklists that week, 419 in all24%
  5. Hartwood Acres ParkAllegheny County, best mid September · 35 checklists that week, 475 in all22%
  6. Lake FrancisLuzerne County, best the second week of September · 37 checklists that week, 940 in all22%

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

Best time of day

In Pennsylvania, the Philadelphia Vireo is most often listed on checklists started between 6 and 8 am (0.4% of those checklists).

0%0.5%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: 0.3% of 92903 checklists7 am: 0.4% of 241233 checklists8 am: 0.3% of 271994 checklists9 am: 0.2% of 236842 checklists10 am: 0.1% of 199508 checklists11 am: 0.1% of 161893 checklists12 pm: 0.1% of 143945 checklists1 pm: 0.1% of 134352 checklists2 pm: 0.1% of 129692 checklists3 pm: 0.1% of 126132 checklists4 pm: 0.1% of 115055 checklists5 pm: 0.1% of 90719 checklists6 pm: 0.1% of 67534 checklists7 pm: 0.1% 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%0%0%0%
February0%0%0%0%
March0%0%0%0%
April0%0%0%0%
May0.1%0.2%0.5%0.1%
June0.1%0.1%0%0%
July0%0%0%0%
August0%0.1%0.1%0.2%
September1.1%2.1%2.7%1.7%
October0.5%0.1%0.1%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Maryland: arrives the second week of September, 1 week later than Pennsylvania
  • District of Columbia: arrives the second week of September, 1 week later than Pennsylvania
  • Delaware: arrives the second week of September, 1 week later than Pennsylvania
  • New Jersey: arrives early September, in the same week than Pennsylvania

Common questions

When do Philadelphia Vireos arrive in Pennsylvania?
Philadelphia Vireos mostly pass through Pennsylvania: they arrive in early September, peak in mid September (2.1% of checklists), and most are gone by early October.
When do Philadelphia Vireos leave Pennsylvania?
Most Philadelphia Vireos have left Pennsylvania by early October, when reports fall below half their usual rate.
When is the best time to see a Philadelphia Vireo in Pennsylvania?
The Philadelphia Vireo is reported most often in mid September, on about 2.1% of Pennsylvania checklists.
Where in Pennsylvania are Philadelphia Vireos seen most often?
By county, Montour County, Wayne County, and Indiana County have the highest peak reporting rates for the Philadelphia Vireo (counties with at least 200 checklists).