WhenToBird

Lophodytes cucullatus · Anatidae

When Do Hooded Mergansers Arrive in Pennsylvania?

Adult male Hooded Merganser
Photo: Justin Flint, CC BY 4.0 via iNaturalist

Hooded Mergansers are winter birds in Pennsylvania: the first arrive in late October, they are common by the second week of November, peak in the second week of March (11% of checklists), and most are gone by the second week of April.

When to look

First arrivalsOct 22-31late October
Common byNov 8-14the second week of November
PeakMar 8-14the second week of March
Most gone byApr 8-14the second week of April

Best: the second week of March. First arrivals late October; most are gone by the second week of April. Peak: on about 11% of Pennsylvania checklists.

  1. Jancommon
  2. Febcommon
  3. Marpeak season
  4. Aprcommon
  5. Mayrare
  6. Junrare
  7. Julnot usually seen
  8. Augnot usually seen
  9. Sepnot usually seen
  10. Octrare
  11. Novcommon
  12. Deccommon

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

0%5%10%15%Jan 1-7: 5.6% of 47145 checklistsJan 8-14: 5.4% of 35840 checklistsJan 15-21: 5.1% of 35423 checklistsJan 22-31: 5.2% of 49126 checklistsFeb 1-7: 4.9% of 36366 checklistsFeb 8-14: 5.0% of 42248 checklistsFeb 15-21: 4.9% of 55888 checklistsFeb 22-28: 8.7% of 42050 checklistsMar 1-7: 12% of 42709 checklistsMar 8-14: 11% of 43985 checklistsMar 15-21: 10% of 44547 checklistsMar 22-31: 8.1% of 66940 checklistsApr 1-7: 5.1% of 51147 checklistsApr 8-14: 3.5% of 54868 checklistsApr 15-21: 2.3% of 57252 checklistsApr 22-30: 1.4% of 81727 checklistsMay 1-7: 1.0% of 76472 checklistsMay 8-14: 0.8% of 79341 checklistsMay 15-21: 0.7% of 61724 checklistsMay 22-31: 0.8% of 70722 checklistsJun 1-7: 0.7% of 45652 checklistsJun 8-14: 0.5% of 41810 checklistsJun 15-21: 0.5% of 38973 checklistsJun 22-30: 0.4% of 44255 checklistsJul 1-7: 0.3% of 34822 checklistsJul 8-14: 0.4% of 31104 checklistsJul 15-21: 0.3% of 29262 checklistsJul 22-31: 0.3% of 41436 checklistsAug 1-7: 0.2% of 29189 checklistsAug 8-14: 0.3% of 28840 checklistsAug 15-21: 0.3% of 29948 checklistsAug 22-31: 0.2% of 48235 checklistsSep 1-7: 0.2% of 37175 checklistsSep 8-14: 0.2% of 36527 checklistsSep 15-21: 0.1% of 37261 checklistsSep 22-30: 0.2% of 43583 checklistsOct 1-7: 0.2% of 35352 checklistsOct 8-14: 0.2% of 35560 checklistsOct 15-21: 0.4% of 33119 checklistsOct 22-31: 1.2% of 44654 checklistsNov 1-7: 2.7% of 32965 checklistsNov 8-14: 5.3% of 31305 checklistsNov 15-21: 6.4% of 29471 checklistsNov 22-30: 7.4% of 38642 checklistsDec 1-7: 7.7% of 28779 checklistsDec 8-14: 6.6% of 29486 checklistsDec 15-21: 5.6% of 37465 checklistsDec 22-31: 5.4% 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. Wyoming CountyBest early December · 73 checklists that week, 6,156 in all35%
  2. Montour CountyBest late November · 91 checklists that week, 6,082 in all32%
  3. Crawford CountyBest mid March · 622 checklists that week, 23,552 in all31%
  4. Mercer CountyBest the second week of March · 456 checklists that week, 17,853 in all24%
  5. Carbon CountyBest the second week of March · 341 checklists that week, 16,269 in all22%
  6. Potter CountyBest mid March · 191 checklists that week, 9,677 in all21%

Best spots

Share of checklists at the peak
  1. Weir LakeMonroe County, best the second week of January · 32 checklists that week, 904 in all96%
  2. East Park ReservoirPhiladelphia County, best late November · 28 checklists that week, 871 in all93%
  3. Upper Perkiomen ValleyMontgomery County, best early December · 65 checklists that week, 3,798 in all92%
  4. Schuylkill River Open SpaceMontgomery County, best early February · 73 checklists that week, 2,272 in all86%
  5. Lake Ontelaunee (Peters Creek)Berks County, best late February · 50 checklists that week, 845 in all86%
  6. Chartiers CreekAllegheny County, best the second week of January · 34 checklists that week, 517 in all84%

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

Best time of day

In Pennsylvania, the Hooded Merganser is most often listed on checklists started between 1 and 3 pm (4.2% of those checklists).

0%2%4%6%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: 1.9% of 92903 checklists7 am: 2.5% of 241233 checklists8 am: 2.8% of 271994 checklists9 am: 3.3% of 236842 checklists10 am: 3.8% of 199508 checklists11 am: 3.9% of 161893 checklists12 pm: 4.0% of 143945 checklists1 pm: 4.1% of 134352 checklists2 pm: 4.2% of 129692 checklists3 pm: 3.9% of 126132 checklists4 pm: 3.5% of 115055 checklists5 pm: 2.5% of 90719 checklists6 pm: 1.9% of 67534 checklists7 pm: 1.3% 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
January5.6%5.4%5.1%5.2%
February4.9%5.0%4.9%8.7%
March12%11%10%8.1%
April5.1%3.5%2.3%1.4%
May1.0%0.8%0.7%0.8%
June0.7%0.5%0.5%0.4%
July0.3%0.4%0.3%0.3%
August0.2%0.3%0.3%0.2%
September0.2%0.2%0.1%0.2%
October0.2%0.2%0.4%1.2%
November2.7%5.3%6.4%7.4%
December7.7%6.6%5.6%5.4%

Neighboring states

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

Common questions

When do Hooded Mergansers arrive in Pennsylvania?
Hooded Mergansers are winter birds in Pennsylvania: the first arrive in late October, they are common by the second week of November, peak in the second week of March (11% of checklists), and most are gone by the second week of April.
When do Hooded Mergansers leave Pennsylvania?
Most Hooded Mergansers 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 Hooded Merganser in Pennsylvania?
The Hooded Merganser is reported most often in the second week of March, on about 11% of Pennsylvania checklists.
Where in Pennsylvania are Hooded Mergansers seen most often?
By county, Wyoming County, Montour County, and Crawford County have the highest peak reporting rates for the Hooded Merganser (counties with at least 200 checklists).