WhenToBird

Setophaga castanea · Parulidae

When Do Bay-breasted Warblers Arrive in New Hampshire?

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

Bay-breasted Warblers mostly pass through New Hampshire: they arrive in mid August, peak in the second week of September (2.8% of checklists), and most are gone by late September.

When to look

First arrivalsAug 15-21mid August
Common byAug 15-21mid August
PeakSep 8-14the second week of September
Most gone bySep 22-30late September

Best: the second week of September. First arrivals mid August; most are gone by late September. Peak: on about 2.8% of New Hampshire checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprnot usually seen
  5. Maypeak season
  6. Juncommon
  7. Julrare
  8. Augcommon
  9. Seppeak season
  10. Octuncommon
  11. Novnot usually seen
  12. Decnot usually seen

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

0%1%2%3%4%Jan 1-7: 0% of 8253 checklistsJan 8-14: 0% of 5998 checklistsJan 15-21: 0% of 5734 checklistsJan 22-31: 0% of 7776 checklistsFeb 1-7: 0% of 5253 checklistsFeb 8-14: 0% of 6802 checklistsFeb 15-21: 0% of 8852 checklistsFeb 22-28: 0% of 5792 checklistsMar 1-7: 0% of 6187 checklistsMar 8-14: 0% of 6977 checklistsMar 15-21: 0% of 7863 checklistsMar 22-31: 0% of 11746 checklistsApr 1-7: 0% of 9329 checklistsApr 8-14: 0% of 10499 checklistsApr 15-21: 0% of 10376 checklistsApr 22-30: 0% of 13086 checklistsMay 1-7: 0.1% of 13198 checklistsMay 8-14: 0.8% of 14980 checklistsMay 15-21: 3.8% of 12487 checklistsMay 22-31: 2.2% of 14294 checklistsJun 1-7: 0.6% of 8974 checklistsJun 8-14: 0.7% of 8395 checklistsJun 15-21: 0.5% of 7670 checklistsJun 22-30: 0.4% of 9188 checklistsJul 1-7: 0.3% of 7707 checklistsJul 8-14: 0.1% of 6554 checklistsJul 15-21: 0.2% of 6636 checklistsJul 22-31: 0.1% of 9599 checklistsAug 1-7: 0.2% of 6436 checklistsAug 8-14: 0.2% of 6477 checklistsAug 15-21: 0.7% of 6510 checklistsAug 22-31: 2.0% of 9762 checklistsSep 1-7: 3.0% of 6700 checklistsSep 8-14: 3.1% of 6012 checklistsSep 15-21: 2.3% of 6238 checklistsSep 22-30: 1.1% of 7619 checklistsOct 1-7: 0.2% of 6702 checklistsOct 8-14: 0.1% of 6863 checklistsOct 15-21: 0% of 6284 checklistsOct 22-31: 0% of 8287 checklistsNov 1-7: 0% of 7584 checklistsNov 8-14: 0% of 6056 checklistsNov 15-21: 0% of 5597 checklistsNov 22-30: 0% of 7140 checklistsDec 1-7: 0% of 4623 checklistsDec 8-14: 0% of 4920 checklistsDec 15-21: 0% of 6416 checklistsDec 22-31: 0% of 7659 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 New Hampshire 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 New Hampshire

Best counties

Share of checklists at the peak
  1. Carroll CountyBest early September · 733 checklists that week, 30,580 in all8.1%
  2. Coos CountyBest early September · 442 checklists that week, 27,719 in all6.0%
  3. Grafton CountyBest the second week of September · 827 checklists that week, 45,699 in all5.1%
  4. Sullivan CountyBest early September · 299 checklists that week, 13,105 in all3.4%
  5. Rockingham CountyBest late May · 3075 checklists that week, 84,864 in all3.3%
  6. Belknap CountyBest late May · 424 checklists that week, 13,295 in all2.8%

Best spots

Share of checklists at the peak
  1. Shaw PondCarroll County, best early September · 22 checklists that week, 190 in all31%
  2. East Inlet PondCoos County, best the second week of June · 20 checklists that week, 116 in all30%
  3. Town of Hampton MarshRockingham County, best the second week of May · 23 checklists that week, 219 in all24%
  4. Hale CoveCarroll County, best the second week of September · 64 checklists that week, 2,611 in all24%
  5. Gosport HarborRockingham County, best late May · 26 checklists that week, 583 in all20%

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

Best time of day

In New Hampshire, the Bay-breasted Warbler is most often listed on checklists started between 6 and 8 am (0.9% of those checklists).

0%0.5%1%1.5%12 am: too few checklists (219) to judge1 am: too few checklists (192) to judge2 am: too few checklists (176) to judge3 am: too few checklists (234) to judge4 am: too few checklists (1042) to judge5 am: too few checklists (6352) to judge6 am: 1.2% of 23140 checklists7 am: 0.8% of 43401 checklists8 am: 0.7% of 48039 checklists9 am: 0.6% of 43328 checklists10 am: 0.4% of 37073 checklists11 am: 0.3% of 32028 checklists12 pm: 0.3% of 27396 checklists1 pm: 0.3% of 25182 checklists2 pm: 0.2% of 24318 checklists3 pm: 0.3% of 21974 checklists4 pm: 0.4% of 17958 checklists5 pm: 0.3% of 14528 checklists6 pm: 0.3% of 9144 checklists7 pm: too few checklists (5341) to judge8 pm: too few checklists (1845) to judge9 pm: too few checklists (578) to judge10 pm: too few checklists (346) to judge11 pm: too few checklists (256) 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%0%
May0.1%0.8%3.8%2.2%
June0.6%0.7%0.5%0.4%
July0.3%0.1%0.2%0.1%
August0.2%0.2%0.7%2.0%
September3.0%3.1%2.3%1.1%
October0.2%0.1%0%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Massachusetts: arrives early May, 14 weeks earlier than New Hampshire
  • Vermont: arrives mid August, in the same week than New Hampshire
  • Rhode Island: arrives early May, 14 weeks earlier than New Hampshire
  • Maine: arrives the second week of August, 1 week earlier than New Hampshire

Common questions

When do Bay-breasted Warblers arrive in New Hampshire?
Bay-breasted Warblers mostly pass through New Hampshire: they arrive in mid August, peak in the second week of September (2.8% of checklists), and most are gone by late September.
When do Bay-breasted Warblers leave New Hampshire?
Most Bay-breasted Warblers have left New Hampshire by late September, when reports fall below half their usual rate.
When is the best time to see a Bay-breasted Warbler in New Hampshire?
The Bay-breasted Warbler is reported most often in the second week of September, on about 2.8% of New Hampshire checklists.
Where in New Hampshire are Bay-breasted Warblers seen most often?
By county, Carroll County, Coos County, and Grafton County have the highest peak reporting rates for the Bay-breasted Warbler (counties with at least 200 checklists).