WhenToBird

Oceanites oceanicus · Oceanitidae

When Do Wilson's Storm-Petrels Arrive in Maine?

Adult Wilson's Storm-Petrel
Photo: Christopher Stephens, CC BY-SA 4.0 via iNaturalist

Wilson's Storm-Petrels mostly pass through Maine: they arrive in late June, peak in the second week of July (1.1% of checklists), and most are gone by mid August.

When to look

First arrivalsJun 22-30late June
Common byJun 22-30late June
PeakJul 8-14the second week of July
Most gone byAug 15-21mid August

Best: the second week of July. First arrivals late June; most are gone by mid August. Peak: on about 1.1% of Maine checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprnot usually seen
  5. Mayrare
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Seprare
  10. Octnot usually seen
  11. Novnot usually seen
  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% 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% of 22556 checklistsMay 8-14: 0.1% of 27842 checklistsMay 15-21: 0.1% of 27748 checklistsMay 22-31: 0.1% of 38715 checklistsJun 1-7: 0.1% of 26916 checklistsJun 8-14: 0.1% of 23737 checklistsJun 15-21: 0.3% of 22733 checklistsJun 22-30: 0.5% of 28248 checklistsJul 1-7: 1.1% of 20290 checklistsJul 8-14: 1.0% of 18534 checklistsJul 15-21: 1.1% of 17319 checklistsJul 22-31: 0.7% of 22815 checklistsAug 1-7: 0.9% of 15004 checklistsAug 8-14: 1.0% of 14603 checklistsAug 15-21: 0.6% of 14972 checklistsAug 22-31: 0.2% of 19813 checklistsSep 1-7: 0.1% of 14567 checklistsSep 8-14: 0.1% of 14520 checklistsSep 15-21: 0.1% of 14339 checklistsSep 22-30: 0.1% of 16879 checklistsOct 1-7: 0% of 12959 checklistsOct 8-14: 0% of 13168 checklistsOct 15-21: 0% of 11184 checklistsOct 22-31: 0% 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. Knox CountyBest the second week of July · 911 checklists that week, 34,453 in all5.7%
  2. York CountyBest the second week of July · 1947 checklists that week, 101,844 in all2.8%
  3. Washington CountyBest the second week of July · 1419 checklists that week, 35,967 in all2.2%
  4. Lincoln CountyBest the second week of July · 1431 checklists that week, 59,429 in all1.9%
  5. Sagadahoc CountyBest late July · 691 checklists that week, 21,736 in all1.7%
  6. Hancock CountyBest the second week of August · 2613 checklists that week, 118,358 in all1.0%

Best spots

Share of checklists at the peak
  1. Seal IslandKnox County, best late July · 36 checklists that week, 206 in all27%
  2. Eastern Egg RockKnox County, best the second week of July · 123 checklists that week, 1,346 in all25%
  3. Petit Manan IslandWashington County, best the second week of July · 51 checklists that week, 680 in all25%
  4. South PointYork County, best early July · 34 checklists that week, 1,022 in all20%
  5. Metinic IslandKnox County, best mid July · 23 checklists that week, 263 in all20%

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

Best time of day

In Maine, the Wilson's Storm-Petrel is most often listed on checklists started between 11 am and 1 pm (0.3% of those checklists).

0%0.5%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: 0.2% of 19895 checklists6 am: 0.1% of 54578 checklists7 am: 0.1% of 92775 checklists8 am: 0.1% of 86962 checklists9 am: 0.2% of 78989 checklists10 am: 0.2% of 70954 checklists11 am: 0.3% of 59331 checklists12 pm: 0.3% of 50943 checklists1 pm: 0.2% of 49775 checklists2 pm: 0.3% of 49001 checklists3 pm: 0.2% of 43252 checklists4 pm: 0.2% of 33413 checklists5 pm: 0.3% 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%0.1%0.1%0.1%
June0.1%0.1%0.3%0.5%
July1.1%1.0%1.1%0.7%
August0.9%1.0%0.6%0.2%
September0.1%0.1%0.1%0.1%
October0%0%0%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

Common questions

When do Wilson's Storm-Petrels arrive in Maine?
Wilson's Storm-Petrels mostly pass through Maine: they arrive in late June, peak in the second week of July (1.1% of checklists), and most are gone by mid August.
When do Wilson's Storm-Petrels leave Maine?
Most Wilson's Storm-Petrels have left Maine by mid August, when reports fall below half their usual rate.
When is the best time to see a Wilson's Storm-Petrel in Maine?
The Wilson's Storm-Petrel is reported most often in the second week of July, on about 1.1% of Maine checklists.
Where in Maine are Wilson's Storm-Petrels seen most often?
By county, Knox County, York County, and Washington County have the highest peak reporting rates for the Wilson's Storm-Petrel (counties with at least 200 checklists).