WhenToBird

Setophaga pensylvanica · Parulidae

When Do Chestnut-sided Warblers Arrive in Maine?

Adult male Chestnut-sided Warbler
Photo: Matt Felperin, CC BY 4.0 via iNaturalist

Chestnut-sided Warblers reach Maine in early May, are common by the second week of May, peak in late May (22% of checklists), and most are gone by the second week of July.

When to look

First arrivalsMay 1-7early May
Common byMay 8-14the second week of May
PeakMay 22-31late May
Most gone byJul 8-14the second week of July

Best: late May. First arrivals early May; most are gone by the second week of July. Peak: on about 22% of Maine checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprrare
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Sepuncommon
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%10%20%30%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: 0.1% of 22602 checklistsMay 1-7: 2.5% of 22556 checklistsMay 8-14: 14% of 27842 checklistsMay 15-21: 26% of 27748 checklistsMay 22-31: 22% of 38715 checklistsJun 1-7: 18% of 26916 checklistsJun 8-14: 17% of 23737 checklistsJun 15-21: 14% of 22733 checklistsJun 22-30: 14% of 28248 checklistsJul 1-7: 12% of 20290 checklistsJul 8-14: 9.7% of 18534 checklistsJul 15-21: 7.3% of 17319 checklistsJul 22-31: 3.8% of 22815 checklistsAug 1-7: 2.9% of 15004 checklistsAug 8-14: 3.2% of 14603 checklistsAug 15-21: 3.4% of 14972 checklistsAug 22-31: 4.0% of 19813 checklistsSep 1-7: 3.9% of 14567 checklistsSep 8-14: 3.2% of 14520 checklistsSep 15-21: 2.1% of 14339 checklistsSep 22-30: 0.9% of 16879 checklistsOct 1-7: 0.3% of 12959 checklistsOct 8-14: 0.1% 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% 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.

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Where in Maine

Best counties

Share of checklists at the peak
  1. Waldo CountyBest late May · 1343 checklists that week, 33,433 in all45%
  2. Aroostook CountyBest late May · 1181 checklists that week, 16,817 in all35%
  3. Penobscot CountyBest late May · 2471 checklists that week, 56,895 in all34%
  4. Somerset CountyBest late May · 797 checklists that week, 12,202 in all29%
  5. Oxford CountyBest early June · 696 checklists that week, 15,115 in all29%
  6. Kennebec CountyBest late May · 2161 checklists that week, 48,185 in all28%

Best spots

Share of checklists at the peak
  1. Long CoveWaldo County, best early June · 91 checklists that week, 2,744 in all93%
  2. Beech HillKnox County, best late May · 44 checklists that week, 448 in all89%
  3. Quill HillFranklin County, best the second week of June · 25 checklists that week, 112 in all86%
  4. Merryspring FoundationKnox County, best late May · 28 checklists that week, 255 in all84%
  5. River Point Conservation AreaCumberland County, best late May · 73 checklists that week, 1,146 in all83%
  6. Town of Cape ElizabethCumberland County, best late May · 36 checklists that week, 367 in all79%

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

Best time of day

In Maine, the Chestnut-sided Warbler is most often listed on checklists started between 5 and 7 am (16% of those checklists).

0%5%10%15%20%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: 20% of 19895 checklists6 am: 14% of 54578 checklists7 am: 9.7% of 92775 checklists8 am: 7.4% of 86962 checklists9 am: 5.8% of 78989 checklists10 am: 4.5% of 70954 checklists11 am: 3.5% of 59331 checklists12 pm: 3.1% of 50943 checklists1 pm: 2.8% of 49775 checklists2 pm: 2.5% of 49001 checklists3 pm: 2.4% of 43252 checklists4 pm: 2.8% of 33413 checklists5 pm: 3.2% of 25547 checklists6 pm: 3.9% 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%0.1%
May2.5%14%26%22%
June18%17%14%14%
July12%9.7%7.3%3.8%
August2.9%3.2%3.4%4.0%
September3.9%3.2%2.1%0.9%
October0.3%0.1%0.1%0.1%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • New Hampshire: arrives late April, 1 week earlier than Maine
  • Massachusetts: arrives late April, 1 week earlier than Maine
  • Vermont: arrives early May, in the same week than Maine
  • Rhode Island: arrives late April, 1 week earlier than Maine

Common questions

When do Chestnut-sided Warblers arrive in Maine?
Chestnut-sided Warblers reach Maine in early May, are common by the second week of May, peak in late May (22% of checklists), and most are gone by the second week of July.
When do Chestnut-sided Warblers leave Maine?
Most Chestnut-sided Warblers have left Maine by the second week of July, when reports fall below half their usual rate. Stragglers are still reported until mid September.
When is the best time to see a Chestnut-sided Warbler in Maine?
The Chestnut-sided Warbler is reported most often in late May, on about 22% of Maine checklists.
Where in Maine are Chestnut-sided Warblers seen most often?
By county, Waldo County, Aroostook County, and Penobscot County have the highest peak reporting rates for the Chestnut-sided Warbler (counties with at least 200 checklists).