WhenToBird

Mergus serrator · Anatidae

When Do Red-breasted Mergansers Arrive in Utah?

Adult male Red-breasted Merganser
Photo: Peter Chen 2.0, CC BY 4.0 via iNaturalist

Red-breasted Mergansers arrive in Utah in late February, peak in the second week of April (4.2% of checklists), and most are gone by mid May.

When to look

First arrivalsFeb 22-28late February
Common byFeb 22-28late February
PeakApr 8-14the second week of April
Most gone byMay 15-21mid May

Best: the second week of April. First arrivals late February; most are gone by mid May. Peak: on about 4.2% of Utah checklists.

  1. Januncommon
  2. Febuncommon
  3. Marcommon
  4. Aprpeak season
  5. Maycommon
  6. Junrare
  7. Julnot usually seen
  8. Augrare
  9. Seprare
  10. Octuncommon
  11. Novcommon
  12. Decuncommon

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

0%2%4%6%Jan 1-7: 0.6% of 10857 checklistsJan 8-14: 0.5% of 8333 checklistsJan 15-21: 0.4% of 8360 checklistsJan 22-31: 0.9% of 10516 checklistsFeb 1-7: 0.7% of 7416 checklistsFeb 8-14: 0.6% of 8082 checklistsFeb 15-21: 0.5% of 9643 checklistsFeb 22-28: 0.8% of 7960 checklistsMar 1-7: 0.7% of 7998 checklistsMar 8-14: 1.1% of 8581 checklistsMar 15-21: 1.6% of 8637 checklistsMar 22-31: 2.6% of 13006 checklistsApr 1-7: 4.3% of 10562 checklistsApr 8-14: 4.4% of 11694 checklistsApr 15-21: 3.8% of 11382 checklistsApr 22-30: 2.7% of 16626 checklistsMay 1-7: 1.7% of 13523 checklistsMay 8-14: 1.0% of 14714 checklistsMay 15-21: 1.0% of 13711 checklistsMay 22-31: 0.5% of 16546 checklistsJun 1-7: 0.1% of 10284 checklistsJun 8-14: 0.1% of 9530 checklistsJun 15-21: 0.1% of 8854 checklistsJun 22-30: 0.1% of 10566 checklistsJul 1-7: 0.1% of 7987 checklistsJul 8-14: 0% of 7471 checklistsJul 15-21: 0.1% of 7240 checklistsJul 22-31: 0.1% of 9329 checklistsAug 1-7: 0.1% of 6521 checklistsAug 8-14: 0.1% of 6423 checklistsAug 15-21: 0.1% of 6208 checklistsAug 22-31: 0.2% of 9089 checklistsSep 1-7: 0.5% of 7081 checklistsSep 8-14: 0.3% of 7306 checklistsSep 15-21: 0.2% of 7208 checklistsSep 22-30: 0.2% of 8876 checklistsOct 1-7: 0.3% of 7265 checklistsOct 8-14: 0.3% of 7226 checklistsOct 15-21: 0.2% of 7007 checklistsOct 22-31: 1.1% of 8443 checklistsNov 1-7: 2.4% of 6711 checklistsNov 8-14: 2.8% of 6290 checklistsNov 15-21: 3.8% of 6169 checklistsNov 22-30: 2.6% of 8228 checklistsDec 1-7: 1.3% of 6011 checklistsDec 8-14: 0.6% of 6044 checklistsDec 15-21: 0.7% of 6721 checklistsDec 22-31: 0.6% 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. Box Elder CountyBest the second week of November · 173 checklists that week, 9,867 in all15%
  2. Piute CountyBest the second week of April · 30 checklists that week, 1,035 in all13%
  3. Summit CountyBest the second week of April · 249 checklists that week, 13,829 in all10%
  4. Duchesne CountyBest the second week of November · 25 checklists that week, 2,692 in all9.2%
  5. Beaver CountyBest early April · 181 checklists that week, 6,956 in all8.3%
  6. Davis CountyBest the second week of April · 958 checklists that week, 39,952 in all8.3%

Best spots

Share of checklists at the peak
  1. Hyrum State ParkCache County, best the second week of April · 23 checklists that week, 791 in all62%
  2. Echo ReservoirSummit County, best early April · 20 checklists that week, 541 in all52%
  3. Willard Bay State Park (Dix Creek)Box Elder County, best late November · 43 checklists that week, 202 in all52%
  4. Rockport State ParkSummit County, best mid April · 39 checklists that week, 1,614 in all51%
  5. Lincoln PointUtah County, best mid November · 23 checklists that week, 346 in all49%

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

Best time of day

In Utah, the Red-breasted Merganser is most often listed on checklists started between 1 and 3 pm (1.4% of those checklists).

0%0.5%1%1.5%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: 0.8% of 11714 checklists7 am: 1.1% of 33209 checklists8 am: 1.0% of 46944 checklists9 am: 1.1% of 46290 checklists10 am: 1.2% of 43144 checklists11 am: 1.2% of 36893 checklists12 pm: 1.3% of 32758 checklists1 pm: 1.3% of 30142 checklists2 pm: 1.4% of 29414 checklists3 pm: 1.3% of 29491 checklists4 pm: 1.2% of 29154 checklists5 pm: 1.2% of 22256 checklists6 pm: 0.9% of 17383 checklists7 pm: 0.7% 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
January0.6%0.5%0.4%0.9%
February0.7%0.6%0.5%0.8%
March0.7%1.1%1.6%2.6%
April4.3%4.4%3.8%2.7%
May1.7%1.0%1.0%0.5%
June0.1%0.1%0.1%0.1%
July0.1%0%0.1%0.1%
August0.1%0.1%0.1%0.2%
September0.5%0.3%0.2%0.2%
October0.3%0.3%0.2%1.1%
November2.4%2.8%3.8%2.6%
December1.3%0.6%0.7%0.6%

Neighboring states

  • Wyoming: arrives early October, 19 weeks earlier than Utah
  • Nevada: arrives early November, 15 weeks earlier than Utah
  • Colorado: arrives late October, 16 weeks earlier than Utah
  • Idaho: arrives mid October, 17 weeks earlier than Utah

Common questions

When do Red-breasted Mergansers arrive in Utah?
Red-breasted Mergansers arrive in Utah in late February, peak in the second week of April (4.2% of checklists), and most are gone by mid May.
When do Red-breasted Mergansers leave Utah?
Most Red-breasted Mergansers have left Utah by mid May, when reports fall below half their usual rate.
When is the best time to see a Red-breasted Merganser in Utah?
The Red-breasted Merganser is reported most often in the second week of April, on about 4.2% of Utah checklists.
Where in Utah are Red-breasted Mergansers seen most often?
By county, Box Elder County, Piute County, and Summit County have the highest peak reporting rates for the Red-breasted Merganser (counties with at least 200 checklists).