WhenToBird

Chroicocephalus philadelphia · Laridae

When Do Bonaparte's Gulls Arrive in Maine?

Adult Bonaparte's Gull
Photo: Kevin Krebs, CC BY 4.0 via iNaturalist

Bonaparte's Gulls reach Maine in early June, are common by the second week of July, peak in the second week of August (6.2% of checklists), and most are gone by late November.

When to look

First arrivalsJun 1-7early June
Common byJul 8-14the second week of July
PeakAug 8-14the second week of August
Most gone byNov 22-30late November

Best: the second week of August. First arrivals early June; most are gone by late November. Peak: on about 6.2% of Maine checklists.

  1. Janrare
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprnot usually seen
  5. Mayuncommon
  6. Jununcommon
  7. Julcommon
  8. Augpeak season
  9. Sepcommon
  10. Octcommon
  11. Novcommon
  12. Decuncommon

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

0%2%4%6%8%Jan 1-7: 0.3% of 15499 checklistsJan 8-14: 0.3% of 11141 checklistsJan 15-21: 0.1% of 10729 checklistsJan 22-31: 0.1% of 15084 checklistsFeb 1-7: 0.1% of 9403 checklistsFeb 8-14: 0.1% of 11268 checklistsFeb 15-21: 0.1% of 14061 checklistsFeb 22-28: 0.1% of 9977 checklistsMar 1-7: 0.1% of 9649 checklistsMar 8-14: 0% of 11781 checklistsMar 15-21: 0.1% of 11613 checklistsMar 22-31: 0.1% of 17798 checklistsApr 1-7: 0.1% of 14638 checklistsApr 8-14: 0.1% of 16511 checklistsApr 15-21: 0.1% of 17164 checklistsApr 22-30: 0.2% of 22602 checklistsMay 1-7: 0.3% of 22556 checklistsMay 8-14: 0.3% of 27842 checklistsMay 15-21: 0.7% of 27748 checklistsMay 22-31: 1.1% of 38715 checklistsJun 1-7: 1.0% of 26916 checklistsJun 8-14: 1.1% of 23737 checklistsJun 15-21: 1.2% of 22733 checklistsJun 22-30: 1.0% of 28248 checklistsJul 1-7: 1.7% of 20290 checklistsJul 8-14: 2.0% of 18534 checklistsJul 15-21: 2.8% of 17319 checklistsJul 22-31: 4.3% of 22815 checklistsAug 1-7: 6.3% of 15004 checklistsAug 8-14: 6.2% of 14603 checklistsAug 15-21: 6.0% of 14972 checklistsAug 22-31: 5.1% of 19813 checklistsSep 1-7: 4.2% of 14567 checklistsSep 8-14: 3.4% of 14520 checklistsSep 15-21: 3.4% of 14339 checklistsSep 22-30: 2.8% of 16879 checklistsOct 1-7: 3.1% of 12959 checklistsOct 8-14: 3.7% of 13168 checklistsOct 15-21: 3.7% of 11184 checklistsOct 22-31: 3.9% of 13717 checklistsNov 1-7: 4.3% of 9823 checklistsNov 8-14: 3.9% of 9007 checklistsNov 15-21: 3.0% of 8528 checklistsNov 22-30: 2.4% of 10228 checklistsDec 1-7: 2.0% of 7505 checklistsDec 8-14: 0.7% of 7982 checklistsDec 15-21: 0.8% of 10455 checklistsDec 22-31: 0.3% 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. Washington CountyBest the second week of August · 1034 checklists that week, 35,967 in all15%
  2. York CountyBest late July · 2602 checklists that week, 101,844 in all14%
  3. Waldo CountyBest mid September · 618 checklists that week, 33,433 in all11%
  4. Lincoln CountyBest late October · 972 checklists that week, 59,429 in all7.9%
  5. Hancock CountyBest mid August · 2564 checklists that week, 118,358 in all7.6%
  6. Sagadahoc CountyBest the second week of August · 401 checklists that week, 21,736 in all6.7%

Best spots

Share of checklists at the peak
  1. Back BayYork County, best the second week of July · 40 checklists that week, 1,607 in all87%
  2. Bridges Ice Pond (historical)York County, best late November · 25 checklists that week, 245 in all78%
  3. Ferry RockCumberland County, best early June · 28 checklists that week, 355 in all71%
  4. Hadley PointHancock County, best the second week of August · 25 checklists that week, 1,341 in all70%
  5. Seapoint BeachYork County, best mid June · 25 checklists that week, 658 in all65%
  6. Raccoon CoveHancock County, best mid August · 22 checklists that week, 352 in all61%

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

Best time of day

In Maine, the Bonaparte's Gull is most often listed on checklists started between 5 and 7 pm (2.2% 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: 1.7% of 19895 checklists6 am: 2.1% of 54578 checklists7 am: 1.9% of 92775 checklists8 am: 1.8% of 86962 checklists9 am: 1.7% of 78989 checklists10 am: 1.7% of 70954 checklists11 am: 1.7% of 59331 checklists12 pm: 1.6% of 50943 checklists1 pm: 1.7% of 49775 checklists2 pm: 1.9% of 49001 checklists3 pm: 1.9% of 43252 checklists4 pm: 2.1% of 33413 checklists5 pm: 2.2% of 25547 checklists6 pm: 2.0% 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
January0.3%0.3%0.1%0.1%
February0.1%0.1%0.1%0.1%
March0.1%0%0.1%0.1%
April0.1%0.1%0.1%0.2%
May0.3%0.3%0.7%1.1%
June1.0%1.1%1.2%1.0%
July1.7%2.0%2.8%4.3%
August6.3%6.2%6.0%5.1%
September4.2%3.4%3.4%2.8%
October3.1%3.7%3.7%3.9%
November4.3%3.9%3.0%2.4%
December2.0%0.7%0.8%0.3%

Neighboring states

  • New Hampshire: arrives the second week of July, 5 weeks later than Maine
  • Massachusetts: arrives mid June, 2 weeks later than Maine
  • Vermont: arrives mid July, 6 weeks later than Maine
  • Rhode Island: arrives the second week of October, 17 weeks later than Maine

Common questions

When do Bonaparte's Gulls arrive in Maine?
Bonaparte's Gulls reach Maine in early June, are common by the second week of July, peak in the second week of August (6.2% of checklists), and most are gone by late November.
When do Bonaparte's Gulls leave Maine?
Most Bonaparte's Gulls have left Maine by late November, when reports fall below half their usual rate. Stragglers are still reported until the second week of December.
When is the best time to see a Bonaparte's Gull in Maine?
The Bonaparte's Gull is reported most often in the second week of August, on about 6.2% of Maine checklists.
Where in Maine are Bonaparte's Gulls seen most often?
By county, Washington County, York County, and Waldo County have the highest peak reporting rates for the Bonaparte's Gull (counties with at least 200 checklists).