WhenToBird

Somateria mollissima · Anatidae

When Do Common Eiders Arrive in Massachusetts?

Adult male Common Eider
Photo: Christoph Moning, CC BY 4.0 via iNaturalist

Common Eiders are in Massachusetts all year, but most are here in winter: numbers build from the second week of November, peak in mid January (15% of checklists), and fall back by the second week of March. In the quietest week (the second week of May) they are still on about 2.9% of checklists.

When to look

Numbers buildNov 8-14the second week of November
PeakJan 15-21mid January
Fall back byMar 8-14the second week of March
FewestMay 8-14the second week of May

Best: mid January. Here all year; numbers build from the second week of November and fall back by the second week of March. Peak: on about 15% of Massachusetts checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marcommon
  4. Aprcommon
  5. Mayuncommon
  6. Jununcommon
  7. Juluncommon
  8. Auguncommon
  9. Sepuncommon
  10. Octcommon
  11. Novcommon
  12. Decpeak season

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

0%5%10%15%20%Jan 1-7: 14% of 43252 checklistsJan 8-14: 15% of 30096 checklistsJan 15-21: 16% of 28760 checklistsJan 22-31: 15% of 38135 checklistsFeb 1-7: 14% of 26442 checklistsFeb 8-14: 13% of 29034 checklistsFeb 15-21: 12% of 37383 checklistsFeb 22-28: 12% of 29977 checklistsMar 1-7: 10% of 29175 checklistsMar 8-14: 8.7% of 32399 checklistsMar 15-21: 8.9% of 34444 checklistsMar 22-31: 7.6% of 49126 checklistsApr 1-7: 6.5% of 36456 checklistsApr 8-14: 5.4% of 40908 checklistsApr 15-21: 4.7% of 42078 checklistsApr 22-30: 3.6% of 56465 checklistsMay 1-7: 3.0% of 56994 checklistsMay 8-14: 2.9% of 64079 checklistsMay 15-21: 2.7% of 52020 checklistsMay 22-31: 3.2% of 55402 checklistsJun 1-7: 3.5% of 30682 checklistsJun 8-14: 3.5% of 27557 checklistsJun 15-21: 3.7% of 26163 checklistsJun 22-30: 3.9% of 29576 checklistsJul 1-7: 4.2% of 23931 checklistsJul 8-14: 4.5% of 22389 checklistsJul 15-21: 4.3% of 22365 checklistsJul 22-31: 4.5% of 32631 checklistsAug 1-7: 4.5% of 25133 checklistsAug 8-14: 4.8% of 24610 checklistsAug 15-21: 5.2% of 25350 checklistsAug 22-31: 4.7% of 37198 checklistsSep 1-7: 4.6% of 27402 checklistsSep 8-14: 4.5% of 27700 checklistsSep 15-21: 4.4% of 28398 checklistsSep 22-30: 4.5% of 34646 checklistsOct 1-7: 4.7% of 28620 checklistsOct 8-14: 5.0% of 30144 checklistsOct 15-21: 5.2% of 28893 checklistsOct 22-31: 7.1% of 38869 checklistsNov 1-7: 8.7% of 29782 checklistsNov 8-14: 11% of 27582 checklistsNov 15-21: 10% of 26642 checklistsNov 22-30: 12% of 34390 checklistsDec 1-7: 11% of 25164 checklistsDec 8-14: 11% of 24892 checklistsDec 15-21: 11% of 29022 checklistsDec 22-31: 15% of 44323 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 Massachusetts 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 Massachusetts

Best counties

Share of checklists at the peak
  1. Essex CountyBest early February · 4211 checklists that week, 213,973 in all39%
  2. Nantucket CountyBest mid March · 318 checklists that week, 23,895 in all35%
  3. Barnstable CountyBest mid November · 3064 checklists that week, 215,188 in all31%
  4. Dukes CountyBest the second week of March · 293 checklists that week, 23,670 in all28%
  5. Suffolk CountyBest late January · 2860 checklists that week, 112,443 in all21%
  6. Plymouth CountyBest early January · 2368 checklists that week, 89,282 in all21%

Best spots

Share of checklists at the peak
  1. Long SwampBarnstable County, best late March · 21 checklists that week, 255 in all100%
  2. Devereux BeachEssex County, best the second week of January · 25 checklists that week, 243 in all100%
  3. Castle Rock BeachEssex County, best the second week of January · 22 checklists that week, 1,043 in all100%
  4. Race RunBarnstable County, best early December · 36 checklists that week, 2,504 in all100%
  5. Nut IslandNorfolk County, best mid November · 25 checklists that week, 356 in all100%
  6. Lighthouse MarshBarnstable County, best late October · 20 checklists that week, 108 in all100%

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

Best time of day

In Massachusetts, the Common Eider is most often listed on checklists started between 11 am and 1 pm (9.7% of those checklists).

0%5%10%12 am: too few checklists (630) to judge1 am: too few checklists (657) to judge2 am: too few checklists (645) to judge3 am: too few checklists (850) to judge4 am: too few checklists (3787) to judge5 am: too few checklists (29743) to judge6 am: 5.0% of 108601 checklists7 am: 5.6% of 186104 checklists8 am: 6.8% of 185905 checklists9 am: 7.9% of 166049 checklists10 am: 9.0% of 150508 checklists11 am: 9.6% of 131024 checklists12 pm: 9.8% of 116804 checklists1 pm: 9.4% of 112055 checklists2 pm: 9.0% of 110246 checklists3 pm: 7.8% of 104376 checklists4 pm: 5.5% of 83736 checklists5 pm: 4.1% of 63723 checklists6 pm: 3.3% of 41435 checklists7 pm: too few checklists (21041) to judge8 pm: too few checklists (5240) to judge9 pm: too few checklists (1722) to judge10 pm: too few checklists (1094) to judge11 pm: too few checklists (704) 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
January14%15%16%15%
February14%13%12%12%
March10%8.7%8.9%7.6%
April6.5%5.4%4.7%3.6%
May3.0%2.9%2.7%3.2%
June3.5%3.5%3.7%3.9%
July4.2%4.5%4.3%4.5%
August4.5%4.8%5.2%4.7%
September4.6%4.5%4.4%4.5%
October4.7%5.0%5.2%7.1%
November8.7%11%10%12%
December11%11%11%15%

Neighboring states

  • Rhode Island: arrives the second week of November, in the same week than Massachusetts
  • New Hampshire: arrives mid December, 5 weeks later than Massachusetts
  • Connecticut: arrives the second week of November, in the same week than Massachusetts
  • Maine: year-round, peaks mid January

Common questions

When do Common Eiders arrive in Massachusetts?
Common Eiders are in Massachusetts all year, but most are here in winter: numbers build from the second week of November, peak in mid January (15% of checklists), and fall back by the second week of March. In the quietest week (the second week of May) they are still on about 2.9% of checklists.
When do Common Eiders leave Massachusetts?
Common Eiders never fully leave Massachusetts: numbers fall back below half their usual rate by the second week of March, but some are still reported in every week, about 2.9% of checklists at the low.
When is the best time to see a Common Eider in Massachusetts?
The Common Eider is reported most often in mid January, on about 15% of Massachusetts checklists.
Where in Massachusetts are Common Eiders seen most often?
By county, Essex County, Nantucket County, and Barnstable County have the highest peak reporting rates for the Common Eider (counties with at least 200 checklists).