WhenToBird

Setophaga castanea · Parulidae

When Do Bay-breasted Warblers Arrive in Maine?

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

Bay-breasted Warblers arrive in Maine in the second week of August, peak in early September (3.1% of checklists), and most are gone by late September.

When to look

First arrivalsAug 8-14the second week of August
Common byAug 8-14the second week of August
PeakSep 1-7early September
Most gone bySep 22-30late September

Best: early September. First arrivals the second week of August; most are gone by late September. Peak: on about 3.1% of Maine checklists.

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

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

0%2%4%6%Jan 1-7: 0% of 15499 checklistsJan 8-14: 0% of 11141 checklistsJan 15-21: 0% of 10729 checklistsJan 22-31: 0% of 15084 checklistsFeb 1-7: 0% of 9403 checklistsFeb 8-14: 0% of 11268 checklistsFeb 15-21: 0% of 14061 checklistsFeb 22-28: 0% of 9977 checklistsMar 1-7: 0% of 9649 checklistsMar 8-14: 0% of 11781 checklistsMar 15-21: 0% of 11613 checklistsMar 22-31: 0% of 17798 checklistsApr 1-7: 0% of 14638 checklistsApr 8-14: 0% of 16511 checklistsApr 15-21: 0% of 17164 checklistsApr 22-30: 0% of 22602 checklistsMay 1-7: 0.1% of 22556 checklistsMay 8-14: 0.8% of 27842 checklistsMay 15-21: 4.5% of 27748 checklistsMay 22-31: 3.3% of 38715 checklistsJun 1-7: 1.0% of 26916 checklistsJun 8-14: 0.6% of 23737 checklistsJun 15-21: 0.6% of 22733 checklistsJun 22-30: 0.6% of 28248 checklistsJul 1-7: 0.4% of 20290 checklistsJul 8-14: 0.4% of 18534 checklistsJul 15-21: 0.3% of 17319 checklistsJul 22-31: 0.2% of 22815 checklistsAug 1-7: 0.3% of 15004 checklistsAug 8-14: 0.5% of 14603 checklistsAug 15-21: 1.7% of 14972 checklistsAug 22-31: 2.7% of 19813 checklistsSep 1-7: 3.6% of 14567 checklistsSep 8-14: 3.2% of 14520 checklistsSep 15-21: 2.3% of 14339 checklistsSep 22-30: 1.1% of 16879 checklistsOct 1-7: 0.6% of 12959 checklistsOct 8-14: 0.2% of 13168 checklistsOct 15-21: 0.1% of 11184 checklistsOct 22-31: 0.1% of 13717 checklistsNov 1-7: 0% of 9823 checklistsNov 8-14: 0% of 9007 checklistsNov 15-21: 0% of 8528 checklistsNov 22-30: 0.1% of 10228 checklistsDec 1-7: 0% of 7505 checklistsDec 8-14: 0% of 7982 checklistsDec 15-21: 0% of 10455 checklistsDec 22-31: 0% of 14285 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 Maine 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.

Embed this map on your site

Where in Maine

Best counties

Share of checklists at the peak
  1. Waldo CountyBest early September · 648 checklists that week, 33,433 in all13%
  2. Franklin CountyBest late August · 366 checklists that week, 14,182 in all11%
  3. Piscataquis CountyBest late August · 405 checklists that week, 14,837 in all10%
  4. Somerset CountyBest the second week of September · 128 checklists that week, 12,202 in all10%
  5. Penobscot CountyBest early September · 914 checklists that week, 56,895 in all6.1%
  6. Lincoln CountyBest mid May · 2206 checklists that week, 59,429 in all5.1%

Best spots

Share of checklists at the peak
  1. Sheepscot River ReservoirLincoln County, best early September · 22 checklists that week, 216 in all44%
  2. Concert ParkPenobscot County, best late August · 20 checklists that week, 472 in all40%
  3. Long CoveWaldo County, best late August · 140 checklists that week, 2,744 in all40%
  4. Town Thatch BedYork County, best the second week of September · 20 checklists that week, 440 in all30%

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

Best time of day

In Maine, the Bay-breasted Warbler is most often listed on checklists started between 5 and 7 am (2.5% of those checklists).

0%1%2%3%12 am: too few checklists (510) to judge1 am: too few checklists (517) to judge2 am: too few checklists (581) to judge3 am: too few checklists (3242) to judge4 am: too few checklists (7221) to judge5 am: 2.8% of 19895 checklists6 am: 2.4% of 54578 checklists7 am: 1.3% of 92775 checklists8 am: 0.9% of 86962 checklists9 am: 0.7% of 78989 checklists10 am: 0.6% of 70954 checklists11 am: 0.5% of 59331 checklists12 pm: 0.4% of 50943 checklists1 pm: 0.4% of 49775 checklists2 pm: 0.4% of 49001 checklists3 pm: 0.4% of 43252 checklists4 pm: 0.5% of 33413 checklists5 pm: 0.4% of 25547 checklists6 pm: 0.3% of 18309 checklists7 pm: too few checklists (14287) to judge8 pm: too few checklists (5336) to judge9 pm: too few checklists (2253) to judge10 pm: too few checklists (1518) to judge11 pm: too few checklists (720) 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%4.5%3.3%
June1.0%0.6%0.6%0.6%
July0.4%0.4%0.3%0.2%
August0.3%0.5%1.7%2.7%
September3.6%3.2%2.3%1.1%
October0.6%0.2%0.1%0.1%
November0%0%0%0.1%
December0%0%0%0%

Neighboring states

  • New Hampshire: arrives mid August, 1 week later than Maine
  • Massachusetts: arrives early May, 13 weeks earlier than Maine
  • Vermont: arrives mid August, 1 week later than Maine
  • Rhode Island: arrives early May, 13 weeks earlier than Maine

Common questions

When do Bay-breasted Warblers arrive in Maine?
Bay-breasted Warblers arrive in Maine in the second week of August, peak in early September (3.1% of checklists), and most are gone by late September.
When do Bay-breasted Warblers leave Maine?
Most Bay-breasted Warblers have left Maine by late September, when reports fall below half their usual rate.
When is the best time to see a Bay-breasted Warbler in Maine?
The Bay-breasted Warbler is reported most often in early September, on about 3.1% of Maine checklists.
Where in Maine are Bay-breasted Warblers seen most often?
By county, Waldo County, Franklin County, and Piscataquis County have the highest peak reporting rates for the Bay-breasted Warbler (counties with at least 200 checklists).