WhenToBird

Phalacrocorax carbo · Phalacrocoracidae

When Do Great Cormorants Arrive in Massachusetts?

Adult Great Cormorant
Photo: bemma, CC BY 4.0 via iNaturalist

Great Cormorants are winter birds in Massachusetts: they arrive in early October, peak in late January (2.9% of checklists), and most are gone by early April.

When to look

First arrivalsOct 1-7early October
Common byOct 1-7early October
PeakJan 22-31late January
Most gone byApr 1-7early April

Best: late January. First arrivals early October; most are gone by early April. Peak: on about 2.9% of Massachusetts checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marcommon
  4. Apruncommon
  5. Mayrare
  6. Junrare
  7. Julnot usually seen
  8. Augrare
  9. Sepuncommon
  10. Octuncommon
  11. Novcommon
  12. Deccommon

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

0%1%2%3%4%Jan 1-7: 2.3% of 43252 checklistsJan 8-14: 2.4% of 30096 checklistsJan 15-21: 2.8% of 28760 checklistsJan 22-31: 2.8% of 38135 checklistsFeb 1-7: 3.1% of 26442 checklistsFeb 8-14: 2.7% of 29034 checklistsFeb 15-21: 2.8% of 37383 checklistsFeb 22-28: 2.5% of 29977 checklistsMar 1-7: 2.2% of 29175 checklistsMar 8-14: 1.8% of 32399 checklistsMar 15-21: 1.9% of 34444 checklistsMar 22-31: 1.4% of 49126 checklistsApr 1-7: 1.0% of 36456 checklistsApr 8-14: 0.7% of 40908 checklistsApr 15-21: 0.5% of 42078 checklistsApr 22-30: 0.4% of 56465 checklistsMay 1-7: 0.3% of 56994 checklistsMay 8-14: 0.2% of 64079 checklistsMay 15-21: 0.2% of 52020 checklistsMay 22-31: 0.2% of 55402 checklistsJun 1-7: 0.1% of 30682 checklistsJun 8-14: 0.1% of 27557 checklistsJun 15-21: 0.1% of 26163 checklistsJun 22-30: 0.1% of 29576 checklistsJul 1-7: 0.1% of 23931 checklistsJul 8-14: 0.1% of 22389 checklistsJul 15-21: 0.1% of 22365 checklistsJul 22-31: 0.1% of 32631 checklistsAug 1-7: 0.1% of 25133 checklistsAug 8-14: 0.1% of 24610 checklistsAug 15-21: 0.1% of 25350 checklistsAug 22-31: 0.2% of 37198 checklistsSep 1-7: 0.3% of 27402 checklistsSep 8-14: 0.4% of 27700 checklistsSep 15-21: 0.6% of 28398 checklistsSep 22-30: 0.8% of 34646 checklistsOct 1-7: 0.8% of 28620 checklistsOct 8-14: 0.9% of 30144 checklistsOct 15-21: 0.9% of 28893 checklistsOct 22-31: 1.1% of 38869 checklistsNov 1-7: 1.3% of 29782 checklistsNov 8-14: 1.3% of 27582 checklistsNov 15-21: 1.3% of 26642 checklistsNov 22-30: 1.4% of 34390 checklistsDec 1-7: 1.6% of 25164 checklistsDec 8-14: 1.5% of 24892 checklistsDec 15-21: 1.6% of 29022 checklistsDec 22-31: 2.0% 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 the second week of February · 4609 checklists that week, 213,973 in all11%
  2. Dukes CountyBest the second week of December · 302 checklists that week, 23,670 in all8.0%
  3. Plymouth CountyBest early February · 1591 checklists that week, 89,282 in all7.9%
  4. Bristol CountyBest mid March · 1260 checklists that week, 65,262 in all4.5%
  5. Nantucket CountyBest the second week of January · 370 checklists that week, 23,895 in all3.0%
  6. Barnstable CountyBest late March · 5312 checklists that week, 215,188 in all2.8%

Best spots

Share of checklists at the peak
  1. Well RockPlymouth County, best the second week of March · 34 checklists that week, 753 in all80%
  2. Green Hill RockPlymouth County, best early February · 21 checklists that week, 298 in all80%
  3. Manomet PointPlymouth County, best mid March · 31 checklists that week, 1,606 in all78%
  4. Manomet Bird ObservatoryPlymouth County, best mid March · 44 checklists that week, 3,294 in all76%
  5. Gull CoveEssex County, best mid March · 41 checklists that week, 1,462 in all76%
  6. Deer Island (Eagle Island)Essex County, best the second week of February · 29 checklists that week, 533 in all65%

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

Best time of day

In Massachusetts, the Great Cormorant is most often listed on checklists started between 11 am and 1 pm (1.5% of those checklists).

0%0.5%1%1.5%2%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: 0.8% of 108601 checklists7 am: 0.8% of 186104 checklists8 am: 1.0% of 185905 checklists9 am: 1.2% of 166049 checklists10 am: 1.4% of 150508 checklists11 am: 1.5% of 131024 checklists12 pm: 1.5% of 116804 checklists1 pm: 1.4% of 112055 checklists2 pm: 1.3% of 110246 checklists3 pm: 1.1% of 104376 checklists4 pm: 0.7% of 83736 checklists5 pm: 0.3% of 63723 checklists6 pm: 0.2% 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
January2.3%2.4%2.8%2.8%
February3.1%2.7%2.8%2.5%
March2.2%1.8%1.9%1.4%
April1.0%0.7%0.5%0.4%
May0.3%0.2%0.2%0.2%
June0.1%0.1%0.1%0.1%
July0.1%0.1%0.1%0.1%
August0.1%0.1%0.1%0.2%
September0.3%0.4%0.6%0.8%
October0.8%0.9%0.9%1.1%
November1.3%1.3%1.3%1.4%
December1.6%1.5%1.6%2.0%

Neighboring states

  • Rhode Island: arrives the second week of September, 3 weeks earlier than Massachusetts
  • New Hampshire: arrives the second week of September, 3 weeks earlier than Massachusetts
  • Connecticut: arrives mid November, 6 weeks later than Massachusetts
  • Maine: arrives the second week of September, 3 weeks earlier than Massachusetts

Common questions

When do Great Cormorants arrive in Massachusetts?
Great Cormorants are winter birds in Massachusetts: they arrive in early October, peak in late January (2.9% of checklists), and most are gone by early April.
When do Great Cormorants leave Massachusetts?
Most Great Cormorants have left Massachusetts by early April, when reports fall below half their usual rate.
When is the best time to see a Great Cormorant in Massachusetts?
The Great Cormorant is reported most often in late January, on about 2.9% of Massachusetts checklists.
Where in Massachusetts are Great Cormorants seen most often?
By county, Essex County, Dukes County, and Plymouth County have the highest peak reporting rates for the Great Cormorant (counties with at least 200 checklists).