WhenToBird

Lophodytes cucullatus · Anatidae

When Do Hooded Mergansers Arrive in Montana?

Adult male Hooded Merganser
Photo: Justin Flint, CC BY 4.0 via iNaturalist

Hooded Mergansers are winter birds in Montana: the first arrive in mid July, they are common by the second week of August, peak in the second week of November (13% of checklists), and most are gone by mid May.

When to look

First arrivalsJul 15-21mid July
Common byAug 8-14the second week of August
PeakNov 8-14the second week of November
Most gone byMay 15-21mid May

Best: the second week of November. First arrivals mid July; most are gone by mid May. Peak: on about 13% of Montana checklists.

  1. Januncommon
  2. Febuncommon
  3. Marcommon
  4. Aprpeak season
  5. Maycommon
  6. Jununcommon
  7. Juluncommon
  8. Auguncommon
  9. Sepuncommon
  10. Octpeak season
  11. Novpeak season
  12. Deccommon

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

0%5%10%15%Jan 1-7: 4.1% of 7987 checklistsJan 8-14: 3.3% of 5561 checklistsJan 15-21: 3.6% of 5613 checklistsJan 22-31: 3.5% of 7881 checklistsFeb 1-7: 3.4% of 5018 checklistsFeb 8-14: 2.7% of 5598 checklistsFeb 15-21: 2.8% of 7247 checklistsFeb 22-28: 3.2% of 5531 checklistsMar 1-7: 4.5% of 6110 checklistsMar 8-14: 5.3% of 6623 checklistsMar 15-21: 6.4% of 7687 checklistsMar 22-31: 8.6% of 11095 checklistsApr 1-7: 9.9% of 7774 checklistsApr 8-14: 10% of 8785 checklistsApr 15-21: 9.9% of 9684 checklistsApr 22-30: 8.2% of 13805 checklistsMay 1-7: 7.0% of 11847 checklistsMay 8-14: 5.2% of 13547 checklistsMay 15-21: 3.6% of 13019 checklistsMay 22-31: 2.5% of 20456 checklistsJun 1-7: 1.9% of 12993 checklistsJun 8-14: 1.7% of 11594 checklistsJun 15-21: 1.6% of 11159 checklistsJun 22-30: 1.5% of 13786 checklistsJul 1-7: 1.5% of 9584 checklistsJul 8-14: 1.5% of 9078 checklistsJul 15-21: 1.9% of 7905 checklistsJul 22-31: 2.4% of 10906 checklistsAug 1-7: 3.4% of 7335 checklistsAug 8-14: 3.9% of 6868 checklistsAug 15-21: 3.8% of 6866 checklistsAug 22-31: 4.5% of 10076 checklistsSep 1-7: 4.0% of 7670 checklistsSep 8-14: 4.7% of 7490 checklistsSep 15-21: 4.6% of 6804 checklistsSep 22-30: 5.1% of 8016 checklistsOct 1-7: 5.3% of 5996 checklistsOct 8-14: 6.5% of 6156 checklistsOct 15-21: 8.8% of 5742 checklistsOct 22-31: 11% of 7790 checklistsNov 1-7: 15% of 5353 checklistsNov 8-14: 13% of 5475 checklistsNov 15-21: 9.8% of 4603 checklistsNov 22-30: 8.8% of 6067 checklistsDec 1-7: 5.7% of 4362 checklistsDec 8-14: 5.6% of 4467 checklistsDec 15-21: 4.8% of 5328 checklistsDec 22-31: 3.4% of 6672 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 Montana 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 Montana

Best counties

Share of checklists at the peak
  1. Powell CountyBest late October · 180 checklists that week, 5,305 in all36%
  2. Rosebud CountyBest late November · 11 checklists that week, 795 in all31%
  3. Musselshell CountyBest early April · 14 checklists that week, 961 in all27%
  4. Lewis and Clark CountyBest the second week of November · 544 checklists that week, 28,806 in all24%
  5. Judith Basin CountyBest late October · 11 checklists that week, 650 in all22%
  6. Ravalli CountyBest mid April · 438 checklists that week, 16,671 in all21%

Best spots

Share of checklists at the peak
  1. Browns LakePowell County, best late October · 46 checklists that week, 433 in all94%
  2. Frenchtown PondMissoula County, best late October · 30 checklists that week, 300 in all93%
  3. Giant Springs State ParkCascade County, best late January · 32 checklists that week, 1,249 in all77%

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

Best time of day

In Montana, the Hooded 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 (183) to judge1 am: too few checklists (169) to judge2 am: too few checklists (163) to judge3 am: too few checklists (212) to judge4 am: too few checklists (503) to judge5 am: too few checklists (4022) to judge6 am: 3.0% of 12719 checklists7 am: 4.4% of 31202 checklists8 am: 5.2% of 47646 checklists9 am: 5.4% of 44624 checklists10 am: 5.3% of 40704 checklists11 am: 5.4% of 33825 checklists12 pm: 5.0% of 29407 checklists1 pm: 5.3% of 27959 checklists2 pm: 5.5% of 26928 checklists3 pm: 5.4% of 25313 checklists4 pm: 5.2% of 22151 checklists5 pm: 5.0% of 16884 checklists6 pm: 4.5% of 13780 checklists7 pm: 3.1% of 9926 checklists8 pm: too few checklists (5765) to judge9 pm: too few checklists (2099) to judge10 pm: too few checklists (595) to judge11 pm: too few checklists (230) 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
January4.1%3.3%3.6%3.5%
February3.4%2.7%2.8%3.2%
March4.5%5.3%6.4%8.6%
April9.9%10%9.9%8.2%
May7.0%5.2%3.6%2.5%
June1.9%1.7%1.6%1.5%
July1.5%1.5%1.9%2.4%
August3.4%3.9%3.8%4.5%
September4.0%4.7%4.6%5.1%
October5.3%6.5%8.8%11%
November15%13%9.8%8.8%
December5.7%5.6%4.8%3.4%

Neighboring states

  • Idaho: arrives the second week of October, 11 weeks later than Montana
  • Wyoming: arrives mid October, 12 weeks later than Montana
  • Utah: arrives late October, 13 weeks later than Montana
  • Washington: arrives early August, 2 weeks later than Montana

Common questions

When do Hooded Mergansers arrive in Montana?
Hooded Mergansers are winter birds in Montana: the first arrive in mid July, they are common by the second week of August, peak in the second week of November (13% of checklists), and most are gone by mid May.
When do Hooded Mergansers leave Montana?
Most Hooded Mergansers have left Montana by mid May, when reports fall below half their usual rate. Stragglers are still reported until early June.
When is the best time to see a Hooded Merganser in Montana?
The Hooded Merganser is reported most often in the second week of November, on about 13% of Montana checklists.
Where in Montana are Hooded Mergansers seen most often?
By county, Powell County, Rosebud County, and Musselshell County have the highest peak reporting rates for the Hooded Merganser (counties with at least 200 checklists).