WhenToBird

Mergus serrator · Anatidae

When Do Red-breasted Mergansers Arrive in Connecticut?

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

Red-breasted Mergansers are winter birds in Connecticut: the first arrive in late October, they are common by late November, peak in late January (15% of checklists), and most are gone by the second week of April.

When to look

First arrivalsOct 22-31late October
Common byNov 22-30late November
PeakJan 22-31late January
Most gone byApr 8-14the second week of April

Best: late January. First arrivals late October; most are gone by the second week of April. Peak: on about 15% of Connecticut checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marpeak season
  4. Aprcommon
  5. Mayrare
  6. Junnot usually seen
  7. Julnot usually seen
  8. Augnot usually seen
  9. Sepnot usually seen
  10. Octrare
  11. Novcommon
  12. Decpeak season

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

0%5%10%15%20%Jan 1-7: 14% of 18950 checklistsJan 8-14: 14% of 13676 checklistsJan 15-21: 13% of 13377 checklistsJan 22-31: 14% of 17004 checklistsFeb 1-7: 16% of 10218 checklistsFeb 8-14: 12% of 11568 checklistsFeb 15-21: 9.4% of 15916 checklistsFeb 22-28: 12% of 11413 checklistsMar 1-7: 12% of 10754 checklistsMar 8-14: 11% of 12051 checklistsMar 15-21: 12% of 12616 checklistsMar 22-31: 12% of 17801 checklistsApr 1-7: 11% of 13186 checklistsApr 8-14: 8.3% of 14428 checklistsApr 15-21: 6.1% of 14738 checklistsApr 22-30: 3.0% of 21753 checklistsMay 1-7: 1.6% of 22494 checklistsMay 8-14: 0.9% of 23363 checklistsMay 15-21: 0.6% of 20219 checklistsMay 22-31: 0.5% of 20778 checklistsJun 1-7: 0.5% of 12234 checklistsJun 8-14: 0.4% of 12491 checklistsJun 15-21: 0.4% of 10856 checklistsJun 22-30: 0.3% of 11964 checklistsJul 1-7: 0.3% of 9437 checklistsJul 8-14: 0.6% of 8599 checklistsJul 15-21: 0.5% of 8252 checklistsJul 22-31: 0.3% of 11329 checklistsAug 1-7: 0.7% of 8116 checklistsAug 8-14: 0.4% of 8051 checklistsAug 15-21: 0.3% of 8502 checklistsAug 22-31: 0.2% of 13673 checklistsSep 1-7: 0.2% of 9873 checklistsSep 8-14: 0.3% of 9735 checklistsSep 15-21: 0.3% of 10120 checklistsSep 22-30: 0.2% of 12543 checklistsOct 1-7: 0.1% of 10735 checklistsOct 8-14: 0.3% of 10869 checklistsOct 15-21: 0.3% of 10436 checklistsOct 22-31: 1.4% of 13808 checklistsNov 1-7: 2.3% of 10507 checklistsNov 8-14: 4.1% of 9827 checklistsNov 15-21: 5.4% of 9904 checklistsNov 22-30: 7.3% of 13396 checklistsDec 1-7: 9.6% of 8974 checklistsDec 8-14: 9.7% of 9468 checklistsDec 15-21: 10% of 11614 checklistsDec 22-31: 14% of 16616 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 Connecticut 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 Connecticut

Best counties

Share of checklists at the peak
  1. New London CountyBest early February · 1468 checklists that week, 65,205 in all33%
  2. Fairfield CountyBest late January · 4195 checklists that week, 139,848 in all24%
  3. New Haven CountyBest late March · 4100 checklists that week, 139,721 in all21%
  4. Middlesex CountyBest mid January · 768 checklists that week, 39,919 in all15%
  5. Litchfield CountyBest the second week of December · 916 checklists that week, 69,766 in all1.1%
  6. Tolland CountyBest mid November · 694 checklists that week, 39,004 in all0.9%

Best spots

Share of checklists at the peak
  1. Stonington PointNew London County, best mid January · 44 checklists that week, 1,092 in all94%
  2. Enders IslandNew London County, best late January · 22 checklists that week, 303 in all93%
  3. Town Open Space (High Street)New London County, best mid February · 45 checklists that week, 742 in all91%
  4. Harkness Memorial State ParkNew London County, best early April · 45 checklists that week, 2,880 in all88%
  5. Greenwich Point ParkFairfield County, best early March · 68 checklists that week, 2,871 in all86%
  6. Fort Hale ParkNew Haven County, best mid February · 20 checklists that week, 498 in all85%

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

Best time of day

In Connecticut, the Red-breasted Merganser is most often listed on checklists started between 1 and 3 pm (7.5% of those checklists).

0%2%4%6%8%12 am: too few checklists (325) to judge1 am: too few checklists (367) to judge2 am: too few checklists (488) to judge3 am: too few checklists (792) to judge4 am: too few checklists (2722) to judge5 am: too few checklists (9489) to judge6 am: 2.2% of 33657 checklists7 am: 4.0% of 62964 checklists8 am: 5.2% of 70645 checklists9 am: 6.2% of 64870 checklists10 am: 7.1% of 58827 checklists11 am: 7.4% of 51689 checklists12 pm: 7.4% of 45288 checklists1 pm: 7.4% of 44765 checklists2 pm: 7.5% of 44173 checklists3 pm: 6.6% of 41979 checklists4 pm: 4.1% of 33219 checklists5 pm: 2.3% of 24828 checklists6 pm: 1.6% of 15856 checklists7 pm: too few checklists (8126) to judge8 pm: too few checklists (1994) to judge9 pm: too few checklists (533) to judge10 pm: too few checklists (349) to judge11 pm: too few checklists (286) 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%14%13%14%
February16%12%9.4%12%
March12%11%12%12%
April11%8.3%6.1%3.0%
May1.6%0.9%0.6%0.5%
June0.5%0.4%0.4%0.3%
July0.3%0.6%0.5%0.3%
August0.7%0.4%0.3%0.2%
September0.2%0.3%0.3%0.2%
October0.1%0.3%0.3%1.4%
November2.3%4.1%5.4%7.3%
December9.6%9.7%10%14%

Neighboring states

  • Rhode Island: arrives mid October, 1 week earlier than Connecticut
  • Massachusetts: arrives the second week of October, 2 weeks earlier than Connecticut
  • New Jersey: arrives early November, 1 week later than Connecticut
  • New York: arrives mid October, 1 week earlier than Connecticut

Common questions

When do Red-breasted Mergansers arrive in Connecticut?
Red-breasted Mergansers are winter birds in Connecticut: the first arrive in late October, they are common by late November, peak in late January (15% of checklists), and most are gone by the second week of April.
When do Red-breasted Mergansers leave Connecticut?
Most Red-breasted Mergansers have left Connecticut by the second week of April, when reports fall below half their usual rate. Stragglers are still reported until early May.
When is the best time to see a Red-breasted Merganser in Connecticut?
The Red-breasted Merganser is reported most often in late January, on about 15% of Connecticut checklists.
Where in Connecticut are Red-breasted Mergansers seen most often?
By county, New London County, Fairfield County, and New Haven County have the highest peak reporting rates for the Red-breasted Merganser (counties with at least 200 checklists).