WhenToBird

Setophaga castanea · Parulidae

When Do Bay-breasted Warblers Arrive in Massachusetts?

Adult Bay-breasted Warbler
Photo: Roger A. Morales-Flores, CC BY 4.0 via iNaturalist

Bay-breasted Warblers mostly pass through Massachusetts: they arrive in early May, peak in mid May (3.7% of checklists), and most are gone by early June.

When to look

First arrivalsMay 1-7early May
Common byMay 1-7early May
PeakMay 15-21mid May
Most gone byJun 1-7early June

Best: mid May. First arrivals early May; most are gone by early June. Peak: on about 3.7% of Massachusetts checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprnot usually seen
  5. Maypeak season
  6. Jununcommon
  7. Julnot usually seen
  8. Augrare
  9. Sepuncommon
  10. Octrare
  11. Novnot usually seen
  12. Decnot usually seen

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

0%2%4%6%8%Jan 1-7: 0% of 43252 checklistsJan 8-14: 0% of 30096 checklistsJan 15-21: 0% of 28760 checklistsJan 22-31: 0% of 38135 checklistsFeb 1-7: 0% of 26442 checklistsFeb 8-14: 0% of 29034 checklistsFeb 15-21: 0% of 37383 checklistsFeb 22-28: 0% of 29977 checklistsMar 1-7: 0% of 29175 checklistsMar 8-14: 0% of 32399 checklistsMar 15-21: 0% of 34444 checklistsMar 22-31: 0% of 49126 checklistsApr 1-7: 0% of 36456 checklistsApr 8-14: 0% of 40908 checklistsApr 15-21: 0.1% of 42078 checklistsApr 22-30: 0% of 56465 checklistsMay 1-7: 0.2% of 56994 checklistsMay 8-14: 2.1% of 64079 checklistsMay 15-21: 7.0% of 52020 checklistsMay 22-31: 2.5% of 55402 checklistsJun 1-7: 0.1% of 30682 checklistsJun 8-14: 0.1% of 27557 checklistsJun 15-21: 0% of 26163 checklistsJun 22-30: 0% of 29576 checklistsJul 1-7: 0% of 23931 checklistsJul 8-14: 0% of 22389 checklistsJul 15-21: 0% of 22365 checklistsJul 22-31: 0% 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: 0.5% of 27402 checklistsSep 8-14: 1.0% of 27700 checklistsSep 15-21: 1.3% of 28398 checklistsSep 22-30: 0.9% of 34646 checklistsOct 1-7: 0.4% of 28620 checklistsOct 8-14: 0.1% of 30144 checklistsOct 15-21: 0.1% of 28893 checklistsOct 22-31: 0.1% of 38869 checklistsNov 1-7: 0.1% of 29782 checklistsNov 8-14: 0.1% of 27582 checklistsNov 15-21: 0.1% of 26642 checklistsNov 22-30: 0.1% of 34390 checklistsDec 1-7: 0% of 25164 checklistsDec 8-14: 0% of 24892 checklistsDec 15-21: 0% of 29022 checklistsDec 22-31: 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 late May · 7201 checklists that week, 213,973 in all6.9%
  2. Suffolk CountyBest late May · 3650 checklists that week, 112,443 in all5.5%
  3. Middlesex CountyBest mid May · 10910 checklists that week, 307,511 in all5.3%
  4. Hampshire CountyBest mid May · 5225 checklists that week, 162,423 in all3.3%
  5. Barnstable CountyBest late May · 7268 checklists that week, 215,188 in all3.2%
  6. Plymouth CountyBest late May · 2734 checklists that week, 89,282 in all2.8%

Best spots

Share of checklists at the peak
  1. Mount GilboaBarnstable County, best late May · 44 checklists that week, 360 in all32%
  2. Halecyon LakeMiddlesex County, best late May · 856 checklists that week, 13,981 in all27%
  3. Blackwater PondBarnstable County, best late May · 240 checklists that week, 3,073 in all24%
  4. Hate CoveEssex County, best late May · 431 checklists that week, 8,243 in all23%
  5. Franklin ParkSuffolk County, best late May · 170 checklists that week, 3,091 in all23%
  6. Parker River National Wildlife RefugeEssex County, best late May · 399 checklists that week, 7,321 in all23%

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

Best time of day

In Massachusetts, the Bay-breasted Warbler is most often listed on checklists started between 6 and 8 am (1.1% 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: 1.6% of 108601 checklists7 am: 0.9% of 186104 checklists8 am: 0.6% of 185905 checklists9 am: 0.5% of 166049 checklists10 am: 0.4% of 150508 checklists11 am: 0.3% of 131024 checklists12 pm: 0.2% of 116804 checklists1 pm: 0.2% of 112055 checklists2 pm: 0.2% of 110246 checklists3 pm: 0.2% of 104376 checklists4 pm: 0.2% of 83736 checklists5 pm: 0.2% 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
January0%0%0%0%
February0%0%0%0%
March0%0%0%0%
April0%0%0.1%0%
May0.2%2.1%7.0%2.5%
June0.1%0.1%0%0%
July0%0%0%0%
August0.1%0.1%0.1%0.2%
September0.5%1.0%1.3%0.9%
October0.4%0.1%0.1%0.1%
November0.1%0.1%0.1%0.1%
December0%0%0%0%

Neighboring states

  • Rhode Island: arrives early May, in the same week than Massachusetts
  • New Hampshire: arrives mid August, 14 weeks later than Massachusetts
  • Connecticut: arrives early May, in the same week than Massachusetts
  • Vermont: arrives mid August, 14 weeks later than Massachusetts

Common questions

When do Bay-breasted Warblers arrive in Massachusetts?
Bay-breasted Warblers mostly pass through Massachusetts: they arrive in early May, peak in mid May (3.7% of checklists), and most are gone by early June.
When do Bay-breasted Warblers leave Massachusetts?
Most Bay-breasted Warblers have left Massachusetts by early June, when reports fall below half their usual rate.
When is the best time to see a Bay-breasted Warbler in Massachusetts?
The Bay-breasted Warbler is reported most often in mid May, on about 3.7% of Massachusetts checklists.
Where in Massachusetts are Bay-breasted Warblers seen most often?
By county, Essex County, Suffolk County, and Middlesex County have the highest peak reporting rates for the Bay-breasted Warbler (counties with at least 200 checklists).