WhenToBird

Mergus merganser · Anatidae

When Do Common Mergansers Arrive in New Jersey?

Adult female Common Merganser
Photo: Christoph Moning, CC BY 4.0 via iNaturalist

Common Mergansers are winter birds in New Jersey: the first arrive in early November, they are common by the second week of December, peak in early March (14% of checklists), and most are gone by the second week of April.

When to look

First arrivalsNov 1-7early November
Common byDec 8-14the second week of December
PeakMar 1-7early March
Most gone byApr 8-14the second week of April

Best: early March. First arrivals early November; most are gone by the second week of April. Peak: on about 14% of New Jersey checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marpeak season
  4. Aprcommon
  5. Mayrare
  6. Junrare
  7. Julnot usually seen
  8. Augrare
  9. Sepnot usually seen
  10. Octrare
  11. Novuncommon
  12. Deccommon

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

0%5%10%15%Jan 1-7: 8.7% of 28167 checklistsJan 8-14: 10% of 20583 checklistsJan 15-21: 10% of 19739 checklistsJan 22-31: 12% of 24586 checklistsFeb 1-7: 12% of 17226 checklistsFeb 8-14: 12% of 19567 checklistsFeb 15-21: 11% of 26553 checklistsFeb 22-28: 15% of 19046 checklistsMar 1-7: 14% of 17969 checklistsMar 8-14: 13% of 18976 checklistsMar 15-21: 12% of 18581 checklistsMar 22-31: 11% of 27590 checklistsApr 1-7: 8.9% of 21202 checklistsApr 8-14: 6.1% of 23609 checklistsApr 15-21: 3.5% of 25056 checklistsApr 22-30: 2.4% of 36679 checklistsMay 1-7: 1.5% of 38378 checklistsMay 8-14: 1.0% of 44071 checklistsMay 15-21: 0.9% of 34076 checklistsMay 22-31: 0.9% of 32558 checklistsJun 1-7: 0.8% of 18049 checklistsJun 8-14: 0.7% of 15597 checklistsJun 15-21: 0.6% of 14894 checklistsJun 22-30: 0.4% of 17187 checklistsJul 1-7: 0.5% of 13406 checklistsJul 8-14: 0.5% of 12550 checklistsJul 15-21: 0.5% of 12358 checklistsJul 22-31: 0.4% of 18382 checklistsAug 1-7: 0.7% of 13689 checklistsAug 8-14: 0.8% of 14006 checklistsAug 15-21: 0.6% of 14483 checklistsAug 22-31: 0.5% of 23182 checklistsSep 1-7: 0.4% of 17984 checklistsSep 8-14: 0.4% of 18320 checklistsSep 15-21: 0.4% of 20491 checklistsSep 22-30: 0.5% of 26176 checklistsOct 1-7: 0.4% of 24112 checklistsOct 8-14: 0.7% of 24603 checklistsOct 15-21: 0.6% of 24549 checklistsOct 22-31: 0.9% of 26206 checklistsNov 1-7: 1.3% of 17469 checklistsNov 8-14: 2.1% of 15102 checklistsNov 15-21: 2.8% of 14958 checklistsNov 22-30: 3.5% of 19447 checklistsDec 1-7: 5.4% of 14017 checklistsDec 8-14: 6.1% of 14625 checklistsDec 15-21: 6.5% of 16937 checklistsDec 22-31: 8.3% of 26651 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 New Jersey 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.

Embed this map on your site

Where in New Jersey

Best counties

Share of checklists at the peak
  1. Hunterdon CountyBest early March · 1194 checklists that week, 57,610 in all34%
  2. Sussex CountyBest the second week of March · 559 checklists that week, 30,305 in all29%
  3. Bergen CountyBest early March · 1364 checklists that week, 73,457 in all28%
  4. Warren CountyBest late January · 555 checklists that week, 20,077 in all28%
  5. Passaic CountyBest the second week of March · 477 checklists that week, 24,933 in all24%
  6. Camden CountyBest early March · 534 checklists that week, 25,931 in all21%

Best spots

Share of checklists at the peak
  1. Cramers CreekHunterdon County, best mid February · 30 checklists that week, 1,218 in all97%
  2. Lake ParsippanyMorris County, best early December · 30 checklists that week, 994 in all96%
  3. Budd LakeMorris County, best late March · 39 checklists that week, 704 in all96%
  4. Lake SolitudeHunterdon County, best late March · 37 checklists that week, 943 in all95%
  5. Oradell ReservoirBergen County, best mid November · 21 checklists that week, 870 in all94%
  6. Spruce Run Recreation AreaHunterdon County, best early March · 154 checklists that week, 7,795 in all94%

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

Best time of day

In New Jersey, the Common Merganser is most often listed on checklists started between 2 and 4 pm (5.5% of those checklists).

0%2%4%6%12 am: too few checklists (746) to judge1 am: too few checklists (640) to judge2 am: too few checklists (606) to judge3 am: too few checklists (755) to judge4 am: too few checklists (1681) to judge5 am: too few checklists (11258) to judge6 am: 3.5% of 50447 checklists7 am: 4.0% of 118312 checklists8 am: 4.5% of 123273 checklists9 am: 4.7% of 107783 checklists10 am: 4.8% of 97537 checklists11 am: 4.9% of 82427 checklists12 pm: 5.1% of 72581 checklists1 pm: 5.0% of 71478 checklists2 pm: 5.5% of 69994 checklists3 pm: 5.5% of 66822 checklists4 pm: 4.4% of 55950 checklists5 pm: 2.7% of 41360 checklists6 pm: 2.2% of 28122 checklists7 pm: too few checklists (14727) to judge8 pm: too few checklists (4257) to judge9 pm: too few checklists (1273) to judge10 pm: too few checklists (920) to judge11 pm: too few checklists (693) 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
January8.7%10%10%12%
February12%12%11%15%
March14%13%12%11%
April8.9%6.1%3.5%2.4%
May1.5%1.0%0.9%0.9%
June0.8%0.7%0.6%0.4%
July0.5%0.5%0.5%0.4%
August0.7%0.8%0.6%0.5%
September0.4%0.4%0.4%0.5%
October0.4%0.7%0.6%0.9%
November1.3%2.1%2.8%3.5%
December5.4%6.1%6.5%8.3%

Neighboring states

  • Delaware: arrives early December, 4 weeks later than New Jersey
  • Connecticut: arrives mid October, 2 weeks earlier than New Jersey
  • Pennsylvania: arrives mid July, 14 weeks earlier than New Jersey
  • New York: arrives mid August, 10 weeks earlier than New Jersey

Common questions

When do Common Mergansers arrive in New Jersey?
Common Mergansers are winter birds in New Jersey: the first arrive in early November, they are common by the second week of December, peak in early March (14% of checklists), and most are gone by the second week of April.
When do Common Mergansers leave New Jersey?
Most Common Mergansers have left New Jersey by the second week of April, when reports fall below half their usual rate. Stragglers are still reported until the second week of May.
When is the best time to see a Common Merganser in New Jersey?
The Common Merganser is reported most often in early March, on about 14% of New Jersey checklists.
Where in New Jersey are Common Mergansers seen most often?
By county, Hunterdon County, Sussex County, and Bergen County have the highest peak reporting rates for the Common Merganser (counties with at least 200 checklists).