WhenToBird

Butorides virescens · Ardeidae

When Do Green Herons Arrive in Pennsylvania?

Adult male Green Heron
Photo: Jonathan Eisen, CC BY 4.0 via iNaturalist

Green Herons reach Pennsylvania in the second week of April, are common by mid April, peak in the second week of August (12% of checklists), and most are gone by late September.

When to look

First arrivalsApr 8-14the second week of April
Common byApr 15-21mid April
PeakAug 8-14the second week of August
Most gone bySep 22-30late September

Best: the second week of August. First arrivals the second week of April; most are gone by late September. Peak: on about 12% of Pennsylvania checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Apruncommon
  5. Maycommon
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octuncommon
  11. Novnot usually seen
  12. Decnot usually seen

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

0%5%10%15%Jan 1-7: 0% of 47145 checklistsJan 8-14: 0.1% 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: 0.1% of 42709 checklistsMar 8-14: 0% of 43985 checklistsMar 15-21: 0% of 44547 checklistsMar 22-31: 0.1% of 66940 checklistsApr 1-7: 0.1% of 51147 checklistsApr 8-14: 0.6% of 54868 checklistsApr 15-21: 2.4% of 57252 checklistsApr 22-30: 4.8% of 81727 checklistsMay 1-7: 5.7% of 76472 checklistsMay 8-14: 5.6% of 79341 checklistsMay 15-21: 5.9% of 61724 checklistsMay 22-31: 5.6% of 70722 checklistsJun 1-7: 5.2% of 45652 checklistsJun 8-14: 4.9% of 41810 checklistsJun 15-21: 5.4% of 38973 checklistsJun 22-30: 5.5% of 44255 checklistsJul 1-7: 6.4% of 34822 checklistsJul 8-14: 8.4% of 31104 checklistsJul 15-21: 9.6% of 29262 checklistsJul 22-31: 11% of 41436 checklistsAug 1-7: 12% of 29189 checklistsAug 8-14: 13% of 28840 checklistsAug 15-21: 12% of 29948 checklistsAug 22-31: 11% of 48235 checklistsSep 1-7: 9.6% of 37175 checklistsSep 8-14: 7.9% of 36527 checklistsSep 15-21: 5.4% of 37261 checklistsSep 22-30: 3.7% of 43583 checklistsOct 1-7: 2.0% of 35352 checklistsOct 8-14: 0.8% of 35560 checklistsOct 15-21: 0.4% of 33119 checklistsOct 22-31: 0.1% of 44654 checklistsNov 1-7: 0.1% of 32965 checklistsNov 8-14: 0.1% 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% 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. Snyder CountyBest the second week of July · 72 checklists that week, 5,676 in all24%
  2. Philadelphia CountyBest early August · 1366 checklists that week, 96,503 in all22%
  3. Montour CountyBest mid August · 46 checklists that week, 6,082 in all21%
  4. Bucks CountyBest late August · 2392 checklists that week, 95,030 in all20%
  5. Lancaster CountyBest early August · 1600 checklists that week, 97,892 in all20%
  6. Westmoreland CountyBest late August · 509 checklists that week, 28,322 in all19%

Best spots

Share of checklists at the peak
  1. Upper Perkiomen ValleyMontgomery County, best early August · 56 checklists that week, 3,798 in all93%
  2. Mason SpringHuntingdon County, best mid May · 102 checklists that week, 1,933 in all90%
  3. Flaugherty RunAllegheny County, best late August · 22 checklists that week, 238 in all89%
  4. Hamburg Borough PoolBerks County, best late August · 23 checklists that week, 470 in all87%
  5. Moreland PondMontgomery County, best late July · 29 checklists that week, 805 in all85%

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

Best time of day

In Pennsylvania, the Green Heron is most often listed on checklists started between 6 and 8 am (5.3% of those checklists).

0%2%4%6%8%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: 7.2% of 92903 checklists7 am: 4.6% of 241233 checklists8 am: 3.7% of 271994 checklists9 am: 3.2% of 236842 checklists10 am: 2.7% of 199508 checklists11 am: 2.4% of 161893 checklists12 pm: 2.3% of 143945 checklists1 pm: 2.2% of 134352 checklists2 pm: 2.1% of 129692 checklists3 pm: 2.1% of 126132 checklists4 pm: 2.6% of 115055 checklists5 pm: 3.9% of 90719 checklists6 pm: 5.2% of 67534 checklists7 pm: 5.4% 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%0.1%0%0%
February0%0%0%0%
March0.1%0%0%0.1%
April0.1%0.6%2.4%4.8%
May5.7%5.6%5.9%5.6%
June5.2%4.9%5.4%5.5%
July6.4%8.4%9.6%11%
August12%13%12%11%
September9.6%7.9%5.4%3.7%
October2.0%0.8%0.4%0.1%
November0.1%0.1%0.1%0.1%
December0.1%0.1%0.1%0%

Neighboring states

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

Common questions

When do Green Herons arrive in Pennsylvania?
Green Herons reach Pennsylvania in the second week of April, are common by mid April, peak in the second week of August (12% of checklists), and most are gone by late September.
When do Green Herons leave Pennsylvania?
Most Green Herons have left Pennsylvania by late September, 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 Green Heron in Pennsylvania?
The Green Heron is reported most often in the second week of August, on about 12% of Pennsylvania checklists.
Where in Pennsylvania are Green Herons seen most often?
By county, Snyder County, Philadelphia County, and Montour County have the highest peak reporting rates for the Green Heron (counties with at least 200 checklists).