WhenToBird

Mergus merganser · Anatidae

When Do Common Mergansers Arrive in District of Columbia?

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

Common Mergansers are winter birds in District of Columbia: the first arrive in mid November, they are common by the second week of December, peak in early February (11% of checklists), and most are gone by mid March.

When to look

First arrivalsNov 15-21mid November
Common byDec 8-14the second week of December
PeakFeb 1-7early February
Most gone byMar 15-21mid March

Best: early February. First arrivals mid November; most are gone by mid March. Peak: on about 11% of District of Columbia checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marpeak season
  4. Apruncommon
  5. Maynot usually seen
  6. Junrare
  7. Julnot usually seen
  8. Augnot usually seen
  9. Sepnot usually seen
  10. Octnot usually seen
  11. Novuncommon
  12. Deccommon

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

0%5%10%15%Jan 1-7: 8.3% of 3043 checklistsJan 8-14: 7.7% of 2367 checklistsJan 15-21: 8.0% of 2140 checklistsJan 22-31: 11% of 2777 checklistsFeb 1-7: 12% of 2012 checklistsFeb 8-14: 10% of 1997 checklistsFeb 15-21: 9.0% of 2544 checklistsFeb 22-28: 12% of 2252 checklistsMar 1-7: 9.6% of 2282 checklistsMar 8-14: 10% of 2350 checklistsMar 15-21: 7.0% of 2432 checklistsMar 22-31: 3.9% of 3898 checklistsApr 1-7: 2.5% of 3221 checklistsApr 8-14: 1.0% of 3396 checklistsApr 15-21: 0.3% of 3718 checklistsApr 22-30: 0.2% of 5725 checklistsMay 1-7: 0.2% of 5415 checklistsMay 8-14: 0.2% of 5268 checklistsMay 15-21: 0.3% of 3741 checklistsMay 22-31: 0.2% of 3605 checklistsJun 1-7: 0.7% of 1902 checklistsJun 8-14: 0.9% of 1762 checklistsJun 15-21: 0.1% of 1637 checklistsJun 22-30: 0.2% of 1727 checklistsJul 1-7: 0.3% of 1471 checklistsJul 8-14: 0.1% of 1353 checklistsJul 15-21: 0.1% of 1297 checklistsJul 22-31: 0.3% of 1980 checklistsAug 1-7: 0.3% of 1465 checklistsAug 8-14: 0.4% of 1311 checklistsAug 15-21: 0.1% of 1669 checklistsAug 22-31: 0.1% of 2631 checklistsSep 1-7: 0.2% of 2482 checklistsSep 8-14: 0% of 2622 checklistsSep 15-21: 0% of 2661 checklistsSep 22-30: 0% of 3393 checklistsOct 1-7: 0.1% of 2457 checklistsOct 8-14: 0% of 2487 checklistsOct 15-21: 0% of 2201 checklistsOct 22-31: 0.1% of 2639 checklistsNov 1-7: 0.1% of 2074 checklistsNov 8-14: 1.0% of 1967 checklistsNov 15-21: 1.2% of 1832 checklistsNov 22-30: 1.9% of 2064 checklistsDec 1-7: 4.0% of 1773 checklistsDec 8-14: 5.0% of 2132 checklistsDec 15-21: 8.0% of 2009 checklistsDec 22-31: 7.9% of 2574 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 District of Columbia 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 District of Columbia

Best counties

Share of checklists at the peak
  1. District of Columbia CountyBest early February · 2012 checklists that week, 121,721 in all11%

Best spots

Share of checklists at the peak
  1. Chesapeake and Ohio Canal National Historical ParkDistrict of Columbia County, best the second week of February · 56 checklists that week, 2,253 in all62%
  2. Georgetown ReservoirDistrict of Columbia County, best late February · 45 checklists that week, 1,495 in all57%
  3. Chesapeake and Ohio Canal National Historical Park (Gillam Branch (historical))District of Columbia County, best early March · 25 checklists that week, 653 in all57%
  4. George Washington Memorial ParkwayDistrict of Columbia County, best the second week of January · 36 checklists that week, 1,054 in all39%
  5. Heritage IslandDistrict of Columbia County, best the second week of February · 42 checklists that week, 3,356 in all33%

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

Best time of day

In District of Columbia, the Common Merganser is most often listed on checklists started between 9 and 11 am (3.5% of those checklists).

0%1%2%3%4%12 am: too few checklists (27) to judge1 am: too few checklists (29) to judge2 am: too few checklists (23) to judge3 am: too few checklists (21) to judge4 am: too few checklists (31) to judge5 am: too few checklists (631) to judge6 am: 1.5% of 7391 checklists7 am: 3.3% of 18497 checklists8 am: 3.4% of 18527 checklists9 am: 3.6% of 13285 checklists10 am: 3.4% of 10722 checklists11 am: 3.2% of 8880 checklists12 pm: 3.1% of 7456 checklists1 pm: 3.0% of 6394 checklists2 pm: 2.8% of 6063 checklists3 pm: 2.6% of 6112 checklists4 pm: 1.9% of 5809 checklists5 pm: 1.5% of 5409 checklists6 pm: 1.0% of 3982 checklists7 pm: too few checklists (1887) to judge8 pm: too few checklists (423) to judge9 pm: too few checklists (79) to judge10 pm: too few checklists (44) to judge11 pm: too few checklists (33) 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
January8.3%7.7%8.0%11%
February12%10%9.0%12%
March9.6%10%7.0%3.9%
April2.5%1.0%0.3%0.2%
May0.2%0.2%0.3%0.2%
June0.7%0.9%0.1%0.2%
July0.3%0.1%0.1%0.3%
August0.3%0.4%0.1%0.1%
September0.2%0%0%0%
October0.1%0%0%0.1%
November0.1%1.0%1.2%1.9%
December4.0%5.0%8.0%7.9%

Neighboring states

  • Maryland: arrives mid November, in the same week than District of Columbia
  • Virginia: arrives early December, 2 weeks later than District of Columbia
  • Delaware: arrives early December, 2 weeks later than District of Columbia
  • Pennsylvania: arrives mid July, 16 weeks earlier than District of Columbia

Common questions

When do Common Mergansers arrive in District of Columbia?
Common Mergansers are winter birds in District of Columbia: the first arrive in mid November, they are common by the second week of December, peak in early February (11% of checklists), and most are gone by mid March.
When do Common Mergansers leave District of Columbia?
Most Common Mergansers have left District of Columbia by mid March, when reports fall below half their usual rate. Stragglers are still reported until the second week of April.
When is the best time to see a Common Merganser in District of Columbia?
The Common Merganser is reported most often in early February, on about 11% of District of Columbia checklists.
Where in District of Columbia are Common Mergansers seen most often?
By county, District of Columbia County have the highest peak reporting rates for the Common Merganser (counties with at least 200 checklists).