WhenToBird

Mergus merganser · Anatidae

When Do Common Mergansers Arrive in Alaska?

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

Common Mergansers are in Alaska all year, but most are here in winter: numbers build from the second week of October, peak in early April (19% of checklists), and fall back by early May. In the quietest week (the second week of August) they are still on about 2.7% of checklists.

When to look

Numbers buildOct 8-14the second week of October
PeakApr 1-7early April
Fall back byMay 1-7early May
FewestAug 8-14the second week of August

Best: early April. Here all year; numbers build from the second week of October and fall back by early May. Peak: on about 19% of Alaska checklists.

  1. Janpeak season
  2. Febcommon
  3. Marpeak season
  4. Aprpeak season
  5. Maycommon
  6. Jununcommon
  7. Juluncommon
  8. Auguncommon
  9. Sepcommon
  10. Octpeak season
  11. Novpeak season
  12. Decpeak season

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

0%5%10%15%20%Jan 1-7: 16% of 3788 checklistsJan 8-14: 13% of 2852 checklistsJan 15-21: 13% of 2810 checklistsJan 22-31: 15% of 3629 checklistsFeb 1-7: 15% of 2519 checklistsFeb 8-14: 13% of 2927 checklistsFeb 15-21: 13% of 3743 checklistsFeb 22-28: 14% of 2846 checklistsMar 1-7: 13% of 2904 checklistsMar 8-14: 13% of 3073 checklistsMar 15-21: 15% of 3359 checklistsMar 22-31: 17% of 5855 checklistsApr 1-7: 19% of 4329 checklistsApr 8-14: 20% of 4949 checklistsApr 15-21: 17% of 7114 checklistsApr 22-30: 15% of 10916 checklistsMay 1-7: 13% of 11827 checklistsMay 8-14: 9.3% of 14115 checklistsMay 15-21: 6.8% of 12152 checklistsMay 22-31: 4.8% of 19919 checklistsJun 1-7: 3.5% of 15816 checklistsJun 8-14: 3.3% of 17194 checklistsJun 15-21: 2.7% of 15943 checklistsJun 22-30: 3.0% of 16192 checklistsJul 1-7: 3.3% of 9815 checklistsJul 8-14: 3.4% of 8263 checklistsJul 15-21: 3.7% of 7081 checklistsJul 22-31: 3.0% of 9434 checklistsAug 1-7: 2.4% of 6380 checklistsAug 8-14: 2.6% of 6258 checklistsAug 15-21: 3.1% of 6114 checklistsAug 22-31: 3.7% of 8189 checklistsSep 1-7: 4.7% of 5848 checklistsSep 8-14: 6.3% of 4853 checklistsSep 15-21: 7.5% of 4415 checklistsSep 22-30: 8.6% of 5086 checklistsOct 1-7: 11% of 3576 checklistsOct 8-14: 12% of 4212 checklistsOct 15-21: 15% of 3339 checklistsOct 22-31: 17% of 4169 checklistsNov 1-7: 17% of 2844 checklistsNov 8-14: 20% of 2753 checklistsNov 15-21: 16% of 2291 checklistsNov 22-30: 15% of 3066 checklistsDec 1-7: 15% of 2199 checklistsDec 8-14: 15% of 2472 checklistsDec 15-21: 15% of 3071 checklistsDec 22-31: 14% of 3442 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 Alaska 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 Alaska

Best counties

Share of checklists at the peak
  1. Haines BoroughBest the second week of November · 61 checklists that week, 1,690 in all53%
  2. Bristol Bay BoroughBest the second week of April · 15 checklists that week, 980 in all50%
  3. Ketchikan Gateway BoroughBest late December · 35 checklists that week, 4,641 in all50%
  4. Hoonah-Angoon Census AreaBest mid November · 57 checklists that week, 8,159 in all47%
  5. Skagway MunicipalityBest mid December · 14 checklists that week, 2,045 in all43%
  6. Wrangell City and BoroughBest late November · 43 checklists that week, 2,509 in all42%

Best spots

Share of checklists at the peak
  1. DeLong LakeAnchorage Municipality, best late October · 21 checklists that week, 164 in all95%
  2. Jewel LakeAnchorage Municipality, best mid October · 21 checklists that week, 209 in all94%
  3. The LagoonKenai Peninsula Borough, best late April · 21 checklists that week, 455 in all92%
  4. Ward LakeKetchikan Gateway Borough, best late October · 21 checklists that week, 619 in all87%
  5. Sitka National Historical ParkSitka City and Borough, best late January · 22 checklists that week, 803 in all87%
  6. Anchor PointKenai Peninsula Borough, best early May · 38 checklists that week, 513 in all81%

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

Best time of day

In Alaska, the Common Merganser is most often listed on checklists started between 12 and 2 pm (10% of those checklists).

0%5%10%15%12 am: too few checklists (549) to judge1 am: too few checklists (365) to judge2 am: too few checklists (291) to judge3 am: too few checklists (624) to judge4 am: too few checklists (1241) to judge5 am: too few checklists (3532) to judge6 am: 5.6% of 9751 checklists7 am: 6.7% of 17236 checklists8 am: 7.9% of 24936 checklists9 am: 8.9% of 30139 checklists10 am: 9.6% of 30866 checklists11 am: 9.9% of 28207 checklists12 pm: 10% of 25650 checklists1 pm: 10% of 24144 checklists2 pm: 9.5% of 23323 checklists3 pm: 8.8% of 20763 checklists4 pm: 8.2% of 18245 checklists5 pm: 7.7% of 14895 checklists6 pm: 7.3% of 11707 checklists7 pm: 6.4% of 9365 checklists8 pm: 5.0% of 6934 checklists9 pm: too few checklists (4176) to judge10 pm: too few checklists (2050) to judge11 pm: too few checklists (952) 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
January16%13%13%15%
February15%13%13%14%
March13%13%15%17%
April19%20%17%15%
May13%9.3%6.8%4.8%
June3.5%3.3%2.7%3.0%
July3.3%3.4%3.7%3.0%
August2.4%2.6%3.1%3.7%
September4.7%6.3%7.5%8.6%
October11%12%15%17%
November17%20%16%15%
December15%15%15%14%

Neighboring states

  • Washington: arrives early November, 3 weeks later than Alaska
  • Oregon: arrives mid August, 7 weeks earlier than Alaska
  • Idaho: arrives mid October, 1 week later than Alaska
  • Montana: arrives the second week of March, 20 weeks later than Alaska

Common questions

When do Common Mergansers arrive in Alaska?
Common Mergansers are in Alaska all year, but most are here in winter: numbers build from the second week of October, peak in early April (19% of checklists), and fall back by early May. In the quietest week (the second week of August) they are still on about 2.7% of checklists.
When do Common Mergansers leave Alaska?
Common Mergansers never fully leave Alaska: numbers fall back below half their usual rate by early May, but some are still reported in every week, about 2.7% of checklists at the low.
When is the best time to see a Common Merganser in Alaska?
The Common Merganser is reported most often in early April, on about 19% of Alaska checklists.
Where in Alaska are Common Mergansers seen most often?
By county, Haines Borough, Bristol Bay Borough, and Ketchikan Gateway Borough have the highest peak reporting rates for the Common Merganser (counties with at least 200 checklists).