WhenToBird

Mergus merganser · Anatidae

When Do Common Mergansers Arrive in Missouri?

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

Common Mergansers are winter birds in Missouri: the first arrive in mid November, they are common by late November, peak in early February (3.9% of checklists), and most are gone by the second week of March.

When to look

First arrivalsNov 15-21mid November
Common byNov 22-30late November
PeakFeb 1-7early February
Most gone byMar 8-14the second week of March

Best: early February. First arrivals mid November; most are gone by the second week of March. Peak: on about 3.9% of Missouri checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marcommon
  4. Aprrare
  5. Maynot usually seen
  6. Junnot usually seen
  7. Julnot usually seen
  8. Augnot usually seen
  9. Sepnot usually seen
  10. Octrare
  11. Novuncommon
  12. Deccommon

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

0%2%4%6%Jan 1-7: 2.9% of 12628 checklistsJan 8-14: 3.8% of 9076 checklistsJan 15-21: 3.1% of 8790 checklistsJan 22-31: 4.2% of 11986 checklistsFeb 1-7: 4.1% of 8987 checklistsFeb 8-14: 3.5% of 10394 checklistsFeb 15-21: 1.9% of 15472 checklistsFeb 22-28: 3.6% of 9917 checklistsMar 1-7: 2.1% of 9877 checklistsMar 8-14: 1.5% of 9570 checklistsMar 15-21: 1.0% of 10274 checklistsMar 22-31: 0.5% of 16156 checklistsApr 1-7: 0.2% of 12774 checklistsApr 8-14: 0.1% of 14048 checklistsApr 15-21: 0.1% of 14894 checklistsApr 22-30: 0.1% of 23288 checklistsMay 1-7: 0.1% of 22645 checklistsMay 8-14: 0.1% of 21384 checklistsMay 15-21: 0.1% of 13989 checklistsMay 22-31: 0.1% of 15784 checklistsJun 1-7: 0.1% of 9691 checklistsJun 8-14: 0.1% of 9036 checklistsJun 15-21: 0.1% of 7907 checklistsJun 22-30: 0.1% of 9831 checklistsJul 1-7: 0% of 8008 checklistsJul 8-14: 0% of 7202 checklistsJul 15-21: 0% of 7151 checklistsJul 22-31: 0.1% of 9833 checklistsAug 1-7: 0.1% of 7639 checklistsAug 8-14: 0% of 7507 checklistsAug 15-21: 0.1% of 7429 checklistsAug 22-31: 0.1% of 11182 checklistsSep 1-7: 0.1% of 9471 checklistsSep 8-14: 0.1% of 8501 checklistsSep 15-21: 0.1% of 8169 checklistsSep 22-30: 0.1% of 11572 checklistsOct 1-7: 0.1% of 9028 checklistsOct 8-14: 0.1% of 9413 checklistsOct 15-21: 0.1% of 8656 checklistsOct 22-31: 0.1% of 11625 checklistsNov 1-7: 0.4% of 8627 checklistsNov 8-14: 0.6% of 8284 checklistsNov 15-21: 1.1% of 8075 checklistsNov 22-30: 1.4% of 10430 checklistsDec 1-7: 1.6% of 7870 checklistsDec 8-14: 2.4% of 7567 checklistsDec 15-21: 2.3% of 9696 checklistsDec 22-31: 2.7% of 13142 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 Missouri 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 Missouri

Best counties

Share of checklists at the peak
  1. Monroe CountyBest late January · 17 checklists that week, 1,048 in all66%
  2. Ralls CountyBest early January · 17 checklists that week, 1,204 in all50%
  3. Macon CountyBest mid December · 38 checklists that week, 1,377 in all47%
  4. Lewis CountyBest late December · 32 checklists that week, 1,047 in all43%
  5. Nodaway CountyBest late February · 13 checklists that week, 834 in all33%
  6. Clay CountyBest early February · 265 checklists that week, 14,361 in all19%

Best spots

Share of checklists at the peak
  1. Lake RemoteClay County, best the second week of February · 20 checklists that week, 898 in all93%
  2. Longview LakeJackson County, best early February · 45 checklists that week, 2,343 in all71%
  3. Alton SloughSt. Charles County, best the second week of February · 125 checklists that week, 7,626 in all70%
  4. Smithville Recreation AreaClay County, best late December · 27 checklists that week, 302 in all69%
  5. Long Branch LakeMacon County, best late December · 22 checklists that week, 572 in all64%
  6. Longview Lake (Mouse Creek)Jackson County, best early February · 26 checklists that week, 590 in all64%

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

Best time of day

In Missouri, the Common Merganser is most often listed on checklists started between 1 and 3 pm (1.6% of those checklists).

0%0.5%1%1.5%2%12 am: too few checklists (205) to judge1 am: too few checklists (179) to judge2 am: too few checklists (204) to judge3 am: too few checklists (216) to judge4 am: too few checklists (630) to judge5 am: too few checklists (5072) to judge6 am: 0.4% of 27231 checklists7 am: 0.6% of 64162 checklists8 am: 0.6% of 67854 checklists9 am: 0.9% of 56515 checklists10 am: 1.1% of 47496 checklists11 am: 1.2% of 38845 checklists12 pm: 1.3% of 33383 checklists1 pm: 1.6% of 32503 checklists2 pm: 1.5% of 32615 checklists3 pm: 1.4% of 32514 checklists4 pm: 1.3% of 30274 checklists5 pm: 0.5% of 23446 checklists6 pm: 0.2% of 16374 checklists7 pm: too few checklists (10236) to judge8 pm: too few checklists (3133) to judge9 pm: too few checklists (722) to judge10 pm: too few checklists (405) to judge11 pm: too few checklists (261) 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
January2.9%3.8%3.1%4.2%
February4.1%3.5%1.9%3.6%
March2.1%1.5%1.0%0.5%
April0.2%0.1%0.1%0.1%
May0.1%0.1%0.1%0.1%
June0.1%0.1%0.1%0.1%
July0%0%0%0.1%
August0.1%0%0.1%0.1%
September0.1%0.1%0.1%0.1%
October0.1%0.1%0.1%0.1%
November0.4%0.6%1.1%1.4%
December1.6%2.4%2.3%2.7%

Neighboring states

  • Iowa: arrives early November, 2 weeks earlier than Missouri
  • Kansas: arrives the second week of November, 1 week earlier than Missouri
  • Illinois: arrives the second week of November, 1 week earlier than Missouri
  • Indiana: arrives late November, 1 week later than Missouri

Common questions

When do Common Mergansers arrive in Missouri?
Common Mergansers are winter birds in Missouri: the first arrive in mid November, they are common by late November, peak in early February (3.9% of checklists), and most are gone by the second week of March.
When do Common Mergansers leave Missouri?
Most Common Mergansers have left Missouri by the second week of March, when reports fall below half their usual rate.
When is the best time to see a Common Merganser in Missouri?
The Common Merganser is reported most often in early February, on about 3.9% of Missouri checklists.
Where in Missouri are Common Mergansers seen most often?
By county, Monroe County, Ralls County, and Macon County have the highest peak reporting rates for the Common Merganser (counties with at least 200 checklists).