WhenToBird

Mergus merganser · Anatidae

When Do Common Mergansers Arrive in Utah?

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

Common Mergansers are winter birds in Utah: the first arrive in mid September, they are common by late October, peak in the second week of March (7.6% of checklists), and most are gone by mid April.

When to look

First arrivalsSep 15-21mid September
Common byOct 22-31late October
PeakMar 8-14the second week of March
Most gone byApr 15-21mid April

Best: the second week of March. First arrivals mid September; most are gone by mid April. Peak: on about 7.6% of Utah checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marpeak season
  4. Aprpeak season
  5. Mayuncommon
  6. Junrare
  7. Julrare
  8. Augrare
  9. Sepuncommon
  10. Octcommon
  11. Novpeak season
  12. Deccommon

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

0%2%4%6%8%Jan 1-7: 5.4% of 10857 checklistsJan 8-14: 6.9% of 8333 checklistsJan 15-21: 6.3% of 8360 checklistsJan 22-31: 6.5% of 10516 checklistsFeb 1-7: 5.7% of 7416 checklistsFeb 8-14: 5.7% of 8082 checklistsFeb 15-21: 6.0% of 9643 checklistsFeb 22-28: 6.3% of 7960 checklistsMar 1-7: 7.3% of 7998 checklistsMar 8-14: 7.6% of 8581 checklistsMar 15-21: 7.9% of 8637 checklistsMar 22-31: 6.8% of 13006 checklistsApr 1-7: 6.9% of 10562 checklistsApr 8-14: 4.9% of 11694 checklistsApr 15-21: 4.4% of 11382 checklistsApr 22-30: 2.6% of 16626 checklistsMay 1-7: 1.7% of 13523 checklistsMay 8-14: 1.3% of 14714 checklistsMay 15-21: 1.0% of 13711 checklistsMay 22-31: 0.9% of 16546 checklistsJun 1-7: 0.6% of 10284 checklistsJun 8-14: 0.7% of 9530 checklistsJun 15-21: 0.6% of 8854 checklistsJun 22-30: 0.4% of 10566 checklistsJul 1-7: 0.3% of 7987 checklistsJul 8-14: 0.3% of 7471 checklistsJul 15-21: 0.3% of 7240 checklistsJul 22-31: 0.4% of 9329 checklistsAug 1-7: 0.4% of 6521 checklistsAug 8-14: 0.3% of 6423 checklistsAug 15-21: 0.5% of 6208 checklistsAug 22-31: 0.5% of 9089 checklistsSep 1-7: 0.8% of 7081 checklistsSep 8-14: 1.0% of 7306 checklistsSep 15-21: 1.0% of 7208 checklistsSep 22-30: 1.2% of 8876 checklistsOct 1-7: 1.3% of 7265 checklistsOct 8-14: 1.2% of 7226 checklistsOct 15-21: 2.0% of 7007 checklistsOct 22-31: 2.9% of 8443 checklistsNov 1-7: 4.9% of 6711 checklistsNov 8-14: 5.7% of 6290 checklistsNov 15-21: 7.2% of 6169 checklistsNov 22-30: 6.7% of 8228 checklistsDec 1-7: 5.0% of 6011 checklistsDec 8-14: 4.8% of 6044 checklistsDec 15-21: 4.1% of 6721 checklistsDec 22-31: 5.3% of 9982 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 Utah 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 Utah

Best counties

Share of checklists at the peak
  1. Daggett CountyBest the second week of December · 10 checklists that week, 1,885 in all26%
  2. Piute CountyBest early April · 17 checklists that week, 1,035 in all25%
  3. Kane CountyBest the second week of January · 46 checklists that week, 6,105 in all25%
  4. Emery CountyBest the second week of March · 55 checklists that week, 2,339 in all23%
  5. Wasatch CountyBest the second week of March · 137 checklists that week, 7,780 in all23%
  6. San Juan CountyBest early February · 24 checklists that week, 6,877 in all21%

Best spots

Share of checklists at the peak
  1. Rockport State ParkSummit County, best the second week of March · 35 checklists that week, 1,614 in all90%
  2. Quail Creek State ParkWashington County, best late January · 42 checklists that week, 904 in all88%
  3. Ivins ReservoirWashington County, best mid January · 31 checklists that week, 1,043 in all84%
  4. Lee Kay State Wildlife CenterSalt Lake County, best early March · 85 checklists that week, 3,804 in all72%
  5. Spencer Number Two Reservoir (historical)Kane County, best late December · 20 checklists that week, 605 in all69%

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

Best time of day

In Utah, the Common Merganser is most often listed on checklists started between 1 and 3 pm (4.5% of those checklists).

0%2%4%6%12 am: too few checklists (242) to judge1 am: too few checklists (178) to judge2 am: too few checklists (169) to judge3 am: too few checklists (162) to judge4 am: too few checklists (284) to judge5 am: too few checklists (1984) to judge6 am: 1.6% of 11714 checklists7 am: 2.3% of 33209 checklists8 am: 2.9% of 46944 checklists9 am: 3.3% of 46290 checklists10 am: 3.8% of 43144 checklists11 am: 4.2% of 36893 checklists12 pm: 4.2% of 32758 checklists1 pm: 4.4% of 30142 checklists2 pm: 4.7% of 29414 checklists3 pm: 4.2% of 29491 checklists4 pm: 3.5% of 29154 checklists5 pm: 2.7% of 22256 checklists6 pm: 1.6% of 17383 checklists7 pm: 1.0% of 13099 checklists8 pm: too few checklists (6647) to judge9 pm: too few checklists (1753) to judge10 pm: too few checklists (599) to judge11 pm: too few checklists (307) 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
January5.4%6.9%6.3%6.5%
February5.7%5.7%6.0%6.3%
March7.3%7.6%7.9%6.8%
April6.9%4.9%4.4%2.6%
May1.7%1.3%1.0%0.9%
June0.6%0.7%0.6%0.4%
July0.3%0.3%0.3%0.4%
August0.4%0.3%0.5%0.5%
September0.8%1.0%1.0%1.2%
October1.3%1.2%2.0%2.9%
November4.9%5.7%7.2%6.7%
December5.0%4.8%4.1%5.3%

Neighboring states

  • Wyoming: arrives mid March, 24 weeks earlier than Utah
  • Nevada: arrives early September, 2 weeks earlier than Utah
  • Colorado: arrives early September, 2 weeks earlier than Utah
  • Idaho: arrives mid October, 4 weeks later than Utah

Common questions

When do Common Mergansers arrive in Utah?
Common Mergansers are winter birds in Utah: the first arrive in mid September, they are common by late October, peak in the second week of March (7.6% of checklists), and most are gone by mid April.
When do Common Mergansers leave Utah?
Most Common Mergansers have left Utah by mid April, when reports fall below half their usual rate. Stragglers are still reported until mid May.
When is the best time to see a Common Merganser in Utah?
The Common Merganser is reported most often in the second week of March, on about 7.6% of Utah checklists.
Where in Utah are Common Mergansers seen most often?
By county, Daggett County, Piute County, and Kane County have the highest peak reporting rates for the Common Merganser (counties with at least 200 checklists).