WhenToBird

Vireo philadelphicus · Vireonidae

When Do Philadelphia Vireos Arrive in Maryland?

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

Philadelphia Vireos mostly pass through Maryland: they arrive in the second week of September, peak in mid September (1.7% of checklists), and most are gone by early October.

When to look

First arrivalsSep 8-14the second week of September
Common bySep 8-14the second week of September
PeakSep 15-21mid September
Most gone byOct 1-7early October

Best: mid September. First arrivals the second week of September; most are gone by early October. Peak: on about 1.7% of Maryland checklists.

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

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

0%0.5%1%1.5%2%Jan 1-7: 0% of 28716 checklistsJan 8-14: 0% of 21449 checklistsJan 15-21: 0% of 21267 checklistsJan 22-31: 0% of 29144 checklistsFeb 1-7: 0% of 21347 checklistsFeb 8-14: 0% of 22166 checklistsFeb 15-21: 0% of 29986 checklistsFeb 22-28: 0% of 22427 checklistsMar 1-7: 0% of 21389 checklistsMar 8-14: 0% of 22192 checklistsMar 15-21: 0% of 22823 checklistsMar 22-31: 0% of 33720 checklistsApr 1-7: 0% of 25513 checklistsApr 8-14: 0% of 27718 checklistsApr 15-21: 0% of 29328 checklistsApr 22-30: 0% of 42595 checklistsMay 1-7: 0.1% of 38532 checklistsMay 8-14: 0.1% of 42722 checklistsMay 15-21: 0.1% of 31936 checklistsMay 22-31: 0.1% of 36903 checklistsJun 1-7: 0% of 23191 checklistsJun 8-14: 0% of 21853 checklistsJun 15-21: 0% of 21000 checklistsJun 22-30: 0% of 25133 checklistsJul 1-7: 0% of 18715 checklistsJul 8-14: 0% of 16376 checklistsJul 15-21: 0% of 15793 checklistsJul 22-31: 0% of 21969 checklistsAug 1-7: 0% of 16013 checklistsAug 8-14: 0% of 15249 checklistsAug 15-21: 0% of 15674 checklistsAug 22-31: 0.1% of 24925 checklistsSep 1-7: 0.6% of 19808 checklistsSep 8-14: 1.3% of 18513 checklistsSep 15-21: 1.9% of 21901 checklistsSep 22-30: 1.9% of 22901 checklistsOct 1-7: 0.5% of 19111 checklistsOct 8-14: 0.1% of 18482 checklistsOct 15-21: 0.1% of 17380 checklistsOct 22-31: 0.1% of 23992 checklistsNov 1-7: 0% of 17915 checklistsNov 8-14: 0% of 18905 checklistsNov 15-21: 0% of 16259 checklistsNov 22-30: 0.1% of 22852 checklistsDec 1-7: 0.1% of 16108 checklistsDec 8-14: 0% of 16512 checklistsDec 15-21: 0% of 18952 checklistsDec 22-31: 0% of 29728 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 Maryland 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 Maryland

Best counties

Share of checklists at the peak
  1. Allegany CountyBest mid September · 476 checklists that week, 18,322 in all4.2%
  2. Harford CountyBest mid September · 586 checklists that week, 39,311 in all3.7%
  3. Baltimore CountyBest mid September · 2538 checklists that week, 136,139 in all3.2%
  4. Garrett CountyBest mid September · 525 checklists that week, 37,616 in all3.1%
  5. Cecil CountyBest mid September · 308 checklists that week, 18,620 in all3.0%
  6. Queen Anne's CountyBest mid September · 454 checklists that week, 26,875 in all2.0%

Best spots

Share of checklists at the peak
  1. Parris N. Glendening Recreation ComplexAllegany County, best mid September · 22 checklists that week, 208 in all21%
  2. Mount Nebo Wildlife Management AreaGarrett County, best mid September · 26 checklists that week, 616 in all19%
  3. Oregon PoolBaltimore County, best mid September · 105 checklists that week, 1,329 in all19%
  4. Jenkins RunBaltimore County, best mid September · 30 checklists that week, 506 in all17%
  5. Finzel Swamp Preserve (Wolf Gap)Allegany County, best mid September · 23 checklists that week, 369 in all16%

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

Best time of day

In Maryland, the Philadelphia Vireo is most often listed on checklists started between 6 and 8 am (0.3% of those checklists).

0%0.5%12 am: too few checklists (486) to judge1 am: too few checklists (451) to judge2 am: too few checklists (447) to judge3 am: too few checklists (766) to judge4 am: too few checklists (2076) to judge5 am: too few checklists (11098) to judge6 am: 0.3% of 56604 checklists7 am: 0.3% of 139255 checklists8 am: 0.2% of 148626 checklists9 am: 0.1% of 126820 checklists10 am: 0.1% of 106973 checklists11 am: 0.1% of 87483 checklists12 pm: 0.1% of 74808 checklists1 pm: 0.1% of 69428 checklists2 pm: 0.1% of 67800 checklists3 pm: 0.1% of 67688 checklists4 pm: 0.1% of 60927 checklists5 pm: 0.1% of 43876 checklists6 pm: 0.1% of 32930 checklists7 pm: too few checklists (19051) to judge8 pm: too few checklists (5708) to judge9 pm: too few checklists (1977) to judge10 pm: too few checklists (1170) to judge11 pm: too few checklists (635) 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%0.1%0.1%0.1%
June0%0%0%0%
July0%0%0%0%
August0%0%0%0.1%
September0.6%1.3%1.9%1.9%
October0.5%0.1%0.1%0.1%
November0%0%0%0.1%
December0.1%0%0%0%

Neighboring states

  • District of Columbia: arrives the second week of September, in the same week than Maryland
  • Delaware: arrives the second week of September, in the same week than Maryland
  • Virginia: arrives the second week of September, in the same week than Maryland
  • Pennsylvania: arrives early September, 1 week earlier than Maryland

Common questions

When do Philadelphia Vireos arrive in Maryland?
Philadelphia Vireos mostly pass through Maryland: they arrive in the second week of September, peak in mid September (1.7% of checklists), and most are gone by early October.
When do Philadelphia Vireos leave Maryland?
Most Philadelphia Vireos have left Maryland by early October, when reports fall below half their usual rate.
When is the best time to see a Philadelphia Vireo in Maryland?
The Philadelphia Vireo is reported most often in mid September, on about 1.7% of Maryland checklists.
Where in Maryland are Philadelphia Vireos seen most often?
By county, Allegany County, Harford County, and Baltimore County have the highest peak reporting rates for the Philadelphia Vireo (counties with at least 200 checklists).