WhenToBird

Larus smithsonianus · Laridae

When Do American Herring Gulls Arrive in Pennsylvania?

Adult American Herring Gull
Photo: Priya Sandhu, CC BY 4.0 via iNaturalist

American Herring Gulls are winter birds in Pennsylvania: the first arrive in late July, they are common by mid October, peak in the second week of January (5.0% of checklists), and most are gone by the second week of April.

When to look

First arrivalsJul 22-31late July
Common byOct 15-21mid October
PeakJan 8-14the second week of January
Most gone byApr 8-14the second week of April

Best: the second week of January. First arrivals late July; most are gone by the second week of April. Peak: on about 5.0% of Pennsylvania checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marpeak season
  4. Aprcommon
  5. Mayuncommon
  6. Junrare
  7. Juluncommon
  8. Auguncommon
  9. Sepuncommon
  10. Octcommon
  11. Novpeak season
  12. Decpeak season

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

0%2%4%6%Jan 1-7: 5.2% of 47145 checklistsJan 8-14: 5.2% of 35840 checklistsJan 15-21: 4.7% of 35423 checklistsJan 22-31: 5.1% of 49126 checklistsFeb 1-7: 4.3% of 36366 checklistsFeb 8-14: 3.6% of 42248 checklistsFeb 15-21: 3.3% of 55888 checklistsFeb 22-28: 4.6% of 42050 checklistsMar 1-7: 3.8% of 42709 checklistsMar 8-14: 3.4% of 43985 checklistsMar 15-21: 3.2% of 44547 checklistsMar 22-31: 2.8% of 66940 checklistsApr 1-7: 2.3% of 51147 checklistsApr 8-14: 2.0% of 54868 checklistsApr 15-21: 1.7% of 57252 checklistsApr 22-30: 1.2% of 81727 checklistsMay 1-7: 0.9% of 76472 checklistsMay 8-14: 1.0% of 79341 checklistsMay 15-21: 1.1% of 61724 checklistsMay 22-31: 0.9% of 70722 checklistsJun 1-7: 0.5% of 45652 checklistsJun 8-14: 0.5% of 41810 checklistsJun 15-21: 0.6% of 38973 checklistsJun 22-30: 0.6% of 44255 checklistsJul 1-7: 0.6% of 34822 checklistsJul 8-14: 0.7% of 31104 checklistsJul 15-21: 1.1% of 29262 checklistsJul 22-31: 0.9% of 41436 checklistsAug 1-7: 1.2% of 29189 checklistsAug 8-14: 1.3% of 28840 checklistsAug 15-21: 1.3% of 29948 checklistsAug 22-31: 1.2% of 48235 checklistsSep 1-7: 1.3% of 37175 checklistsSep 8-14: 1.0% of 36527 checklistsSep 15-21: 1.1% of 37261 checklistsSep 22-30: 1.3% of 43583 checklistsOct 1-7: 1.4% of 35352 checklistsOct 8-14: 1.6% of 35560 checklistsOct 15-21: 1.7% of 33119 checklistsOct 22-31: 2.3% of 44654 checklistsNov 1-7: 2.4% of 32965 checklistsNov 8-14: 3.1% of 31305 checklistsNov 15-21: 3.3% of 29471 checklistsNov 22-30: 4.4% of 38642 checklistsDec 1-7: 4.7% of 28779 checklistsDec 8-14: 4.3% of 29486 checklistsDec 15-21: 3.9% of 37465 checklistsDec 22-31: 4.6% 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. Erie CountyBest the second week of December · 645 checklists that week, 49,012 in all28%
  2. Philadelphia CountyBest mid December · 1403 checklists that week, 96,503 in all23%
  3. Mercer CountyBest mid March · 447 checklists that week, 17,853 in all14%
  4. Bucks CountyBest early December · 1455 checklists that week, 95,030 in all14%
  5. Armstrong CountyBest mid February · 393 checklists that week, 11,221 in all11%
  6. Allegheny CountyBest late January · 3666 checklists that week, 152,989 in all9.6%

Best spots

Share of checklists at the peak
  1. Ridge PondErie County, best late September · 41 checklists that week, 1,112 in all100%
  2. Williamson ParkBucks County, best mid October · 41 checklists that week, 780 in all95%
  3. McClure ParkDelaware County, best late January · 35 checklists that week, 541 in all94%
  4. Dry Brooks Day-Use AreaBerks County, best mid December · 49 checklists that week, 1,039 in all90%
  5. Lake NockamixonBucks County, best mid February · 83 checklists that week, 1,542 in all90%
  6. Deadman Island (historical)Allegheny County, best late May · 33 checklists that week, 817 in all89%

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

Best time of day

In Pennsylvania, the American Herring Gull is most often listed on checklists started between 1 and 3 pm (3.0% of those checklists).

0%1%2%3%4%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: 1.8% of 92903 checklists7 am: 2.2% of 241233 checklists8 am: 2.0% of 271994 checklists9 am: 2.2% of 236842 checklists10 am: 2.4% of 199508 checklists11 am: 2.7% of 161893 checklists12 pm: 2.7% of 143945 checklists1 pm: 2.9% of 134352 checklists2 pm: 3.1% of 129692 checklists3 pm: 2.9% of 126132 checklists4 pm: 2.4% of 115055 checklists5 pm: 1.6% of 90719 checklists6 pm: 1.1% of 67534 checklists7 pm: 0.9% 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
January5.2%5.2%4.7%5.1%
February4.3%3.6%3.3%4.6%
March3.8%3.4%3.2%2.8%
April2.3%2.0%1.7%1.2%
May0.9%1.0%1.1%0.9%
June0.5%0.5%0.6%0.6%
July0.6%0.7%1.1%0.9%
August1.2%1.3%1.3%1.2%
September1.3%1.0%1.1%1.3%
October1.4%1.6%1.7%2.3%
November2.4%3.1%3.3%4.4%
December4.7%4.3%3.9%4.6%

Neighboring states

  • Maryland: arrives mid October, 11 weeks later than Pennsylvania
  • District of Columbia: arrives early October, 9 weeks later than Pennsylvania
  • Delaware: arrives early October, 9 weeks later than Pennsylvania
  • New Jersey: year-round, peaks the second week of January

Common questions

When do American Herring Gulls arrive in Pennsylvania?
American Herring Gulls are winter birds in Pennsylvania: the first arrive in late July, they are common by mid October, peak in the second week of January (5.0% of checklists), and most are gone by the second week of April.
When do American Herring Gulls leave Pennsylvania?
Most American Herring Gulls have left Pennsylvania by the second week of April, when reports fall below half their usual rate. Stragglers are still reported until early May.
When is the best time to see a American Herring Gull in Pennsylvania?
The American Herring Gull is reported most often in the second week of January, on about 5.0% of Pennsylvania checklists.
Where in Pennsylvania are American Herring Gulls seen most often?
By county, Erie County, Philadelphia County, and Mercer County have the highest peak reporting rates for the American Herring Gull (counties with at least 200 checklists).