WhenToBird

Botaurus lentiginosus · Ardeidae

When Do American Bitterns Arrive in Maine?

Adult American Bittern
Photo: Kathy Richardson, CC BY 4.0 via iNaturalist

American Bitterns arrive in Maine in mid April, peak in the second week of May (1.4% of checklists), and most are gone by late September.

When to look

First arrivalsApr 15-21mid April
Common byApr 15-21mid April
PeakMay 8-14the second week of May
Most gone bySep 22-30late September

Best: the second week of May. First arrivals mid April; most are gone by late September. Peak: on about 1.4% of Maine checklists.

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

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

0%0.5%1%1.5%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: 0.1% of 17798 checklistsApr 1-7: 0.1% of 14638 checklistsApr 8-14: 0.2% of 16511 checklistsApr 15-21: 0.6% of 17164 checklistsApr 22-30: 1.0% of 22602 checklistsMay 1-7: 1.4% of 22556 checklistsMay 8-14: 1.2% of 27842 checklistsMay 15-21: 1.4% of 27748 checklistsMay 22-31: 1.3% of 38715 checklistsJun 1-7: 1.2% of 26916 checklistsJun 8-14: 1.0% of 23737 checklistsJun 15-21: 1.0% of 22733 checklistsJun 22-30: 0.7% of 28248 checklistsJul 1-7: 0.6% of 20290 checklistsJul 8-14: 0.6% of 18534 checklistsJul 15-21: 0.6% of 17319 checklistsJul 22-31: 0.5% of 22815 checklistsAug 1-7: 0.5% of 15004 checklistsAug 8-14: 0.4% of 14603 checklistsAug 15-21: 0.4% of 14972 checklistsAug 22-31: 0.4% of 19813 checklistsSep 1-7: 0.4% of 14567 checklistsSep 8-14: 0.2% of 14520 checklistsSep 15-21: 0.4% of 14339 checklistsSep 22-30: 0.4% of 16879 checklistsOct 1-7: 0.2% 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: 0.1% of 9823 checklistsNov 8-14: 0.1% of 9007 checklistsNov 15-21: 0.1% of 8528 checklistsNov 22-30: 0% of 10228 checklistsDec 1-7: 0% of 7505 checklistsDec 8-14: 0.1% of 7982 checklistsDec 15-21: 0% of 10455 checklistsDec 22-31: 0.1% 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. Penobscot CountyBest early May · 1764 checklists that week, 56,895 in all6.0%
  2. Aroostook CountyBest mid May · 507 checklists that week, 16,817 in all4.5%
  3. Piscataquis CountyBest mid May · 358 checklists that week, 14,837 in all4.3%
  4. Franklin CountyBest mid May · 519 checklists that week, 14,182 in all3.5%
  5. Somerset CountyBest the second week of May · 315 checklists that week, 12,202 in all3.3%
  6. Waldo CountyBest the second week of May · 1182 checklists that week, 33,433 in all3.0%

Best spots

Share of checklists at the peak
  1. Prays Brook Marsh PreserveHancock County, best early May · 30 checklists that week, 304 in all64%
  2. City of Bangor (Stillwater Avenue)Penobscot County, best the second week of May · 26 checklists that week, 374 in all62%
  3. Great Meadow (Sieur de Monts Spring)Hancock County, best the second week of May · 48 checklists that week, 477 in all31%

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

Best time of day

In Maine, the American Bittern is most often listed on checklists started between 5 and 7 am (1.4% 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: 2.2% of 19895 checklists6 am: 1.1% of 54578 checklists7 am: 0.6% of 92775 checklists8 am: 0.4% of 86962 checklists9 am: 0.3% of 78989 checklists10 am: 0.3% of 70954 checklists11 am: 0.2% of 59331 checklists12 pm: 0.2% of 50943 checklists1 pm: 0.2% of 49775 checklists2 pm: 0.2% of 49001 checklists3 pm: 0.2% of 43252 checklists4 pm: 0.4% of 33413 checklists5 pm: 0.5% of 25547 checklists6 pm: 1.0% 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%0.1%
April0.1%0.2%0.6%1.0%
May1.4%1.2%1.4%1.3%
June1.2%1.0%1.0%0.7%
July0.6%0.6%0.6%0.5%
August0.5%0.4%0.4%0.4%
September0.4%0.2%0.4%0.4%
October0.2%0.1%0.1%0.1%
November0.1%0.1%0.1%0%
December0%0.1%0%0.1%

Neighboring states

  • New Hampshire: arrives mid April, in the same week than Maine
  • Vermont: arrives mid April, in the same week than Maine
  • New York: arrives early April, 2 weeks earlier than Maine
  • New Jersey: arrives early September, 18 weeks later than Maine

Common questions

When do American Bitterns arrive in Maine?
American Bitterns arrive in Maine in mid April, peak in the second week of May (1.4% of checklists), and most are gone by late September.
When do American Bitterns leave Maine?
Most American Bitterns have left Maine by late September, when reports fall below half their usual rate.
When is the best time to see a American Bittern in Maine?
The American Bittern is reported most often in the second week of May, on about 1.4% of Maine checklists.
Where in Maine are American Bitterns seen most often?
By county, Penobscot County, Aroostook County, and Piscataquis County have the highest peak reporting rates for the American Bittern (counties with at least 200 checklists).