WhenToBird

Chroicocephalus philadelphia · Laridae

When Do Bonaparte's Gulls Arrive in Massachusetts?

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

Bonaparte's Gulls are winter birds in Massachusetts: they arrive in mid June, peak in early November (2.9% of checklists), and most are gone by the second week of January.

When to look

First arrivalsJun 15-21mid June
Common byJun 15-21mid June
PeakNov 1-7early November
Most gone byJan 8-14the second week of January

Best: early November. First arrivals mid June; most are gone by the second week of January. Peak: on about 2.9% of Massachusetts checklists.

  1. Januncommon
  2. Febrare
  3. Marrare
  4. Apruncommon
  5. Mayuncommon
  6. Jununcommon
  7. Julcommon
  8. Augcommon
  9. Sepcommon
  10. Octpeak season
  11. Novpeak season
  12. Deccommon

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

0%1%2%3%4%Jan 1-7: 0.8% of 43252 checklistsJan 8-14: 0.6% of 30096 checklistsJan 15-21: 0.5% of 28760 checklistsJan 22-31: 0.5% of 38135 checklistsFeb 1-7: 0.2% of 26442 checklistsFeb 8-14: 0.2% of 29034 checklistsFeb 15-21: 0.2% of 37383 checklistsFeb 22-28: 0.2% of 29977 checklistsMar 1-7: 0.2% of 29175 checklistsMar 8-14: 0.2% of 32399 checklistsMar 15-21: 0.2% of 34444 checklistsMar 22-31: 0.2% of 49126 checklistsApr 1-7: 0.7% of 36456 checklistsApr 8-14: 0.4% of 40908 checklistsApr 15-21: 0.5% of 42078 checklistsApr 22-30: 0.5% of 56465 checklistsMay 1-7: 0.9% of 56994 checklistsMay 8-14: 0.6% of 64079 checklistsMay 15-21: 0.7% of 52020 checklistsMay 22-31: 0.8% of 55402 checklistsJun 1-7: 0.5% of 30682 checklistsJun 8-14: 0.6% of 27557 checklistsJun 15-21: 0.7% of 26163 checklistsJun 22-30: 0.7% of 29576 checklistsJul 1-7: 0.7% of 23931 checklistsJul 8-14: 1.0% of 22389 checklistsJul 15-21: 1.1% of 22365 checklistsJul 22-31: 1.5% of 32631 checklistsAug 1-7: 1.8% of 25133 checklistsAug 8-14: 1.6% of 24610 checklistsAug 15-21: 1.7% of 25350 checklistsAug 22-31: 1.5% of 37198 checklistsSep 1-7: 1.5% of 27402 checklistsSep 8-14: 1.0% of 27700 checklistsSep 15-21: 1.1% of 28398 checklistsSep 22-30: 1.1% of 34646 checklistsOct 1-7: 1.3% of 28620 checklistsOct 8-14: 1.5% of 30144 checklistsOct 15-21: 1.8% of 28893 checklistsOct 22-31: 2.7% of 38869 checklistsNov 1-7: 2.8% of 29782 checklistsNov 8-14: 3.2% of 27582 checklistsNov 15-21: 2.1% of 26642 checklistsNov 22-30: 2.6% of 34390 checklistsDec 1-7: 1.6% of 25164 checklistsDec 8-14: 1.0% of 24892 checklistsDec 15-21: 0.8% of 29022 checklistsDec 22-31: 1.1% of 44323 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 Massachusetts 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 Massachusetts

Best counties

Share of checklists at the peak
  1. Barnstable CountyBest mid November · 3064 checklists that week, 215,188 in all12%
  2. Nantucket CountyBest mid November · 344 checklists that week, 23,895 in all9.7%
  3. Dukes CountyBest late November · 443 checklists that week, 23,670 in all6.4%
  4. Plymouth CountyBest early November · 1565 checklists that week, 89,282 in all4.9%
  5. Essex CountyBest the second week of August · 2880 checklists that week, 213,973 in all4.7%
  6. Suffolk CountyBest late August · 2478 checklists that week, 112,443 in all3.3%

Best spots

Share of checklists at the peak
  1. Race RunBarnstable County, best early November · 54 checklists that week, 2,504 in all91%
  2. Joppa ParkEssex County, best the second week of August · 21 checklists that week, 928 in all86%
  3. Cape Cod National SeashoreBarnstable County, best early November · 64 checklists that week, 3,402 in all79%
  4. Lynn Shore ReservationEssex County, best mid October · 20 checklists that week, 894 in all78%
  5. Pines Point ofSuffolk County, best late July · 27 checklists that week, 679 in all77%
  6. Diamond Creek MarshesSuffolk County, best late October · 20 checklists that week, 922 in all68%

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

Best time of day

In Massachusetts, the Bonaparte's Gull is most often listed on checklists started between 6 and 8 am (1.1% of those checklists).

0%0.5%1%1.5%12 am: too few checklists (630) to judge1 am: too few checklists (657) to judge2 am: too few checklists (645) to judge3 am: too few checklists (850) to judge4 am: too few checklists (3787) to judge5 am: too few checklists (29743) to judge6 am: 1.4% of 108601 checklists7 am: 1.0% of 186104 checklists8 am: 1.0% of 185905 checklists9 am: 1.0% of 166049 checklists10 am: 1.0% of 150508 checklists11 am: 1.0% of 131024 checklists12 pm: 1.1% of 116804 checklists1 pm: 1.0% of 112055 checklists2 pm: 1.0% of 110246 checklists3 pm: 0.9% of 104376 checklists4 pm: 0.7% of 83736 checklists5 pm: 0.7% of 63723 checklists6 pm: 0.6% of 41435 checklists7 pm: too few checklists (21041) to judge8 pm: too few checklists (5240) to judge9 pm: too few checklists (1722) to judge10 pm: too few checklists (1094) to judge11 pm: too few checklists (704) 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
January0.8%0.6%0.5%0.5%
February0.2%0.2%0.2%0.2%
March0.2%0.2%0.2%0.2%
April0.7%0.4%0.5%0.5%
May0.9%0.6%0.7%0.8%
June0.5%0.6%0.7%0.7%
July0.7%1.0%1.1%1.5%
August1.8%1.6%1.7%1.5%
September1.5%1.0%1.1%1.1%
October1.3%1.5%1.8%2.7%
November2.8%3.2%2.1%2.6%
December1.6%1.0%0.8%1.1%

Neighboring states

  • Rhode Island: arrives the second week of October, 15 weeks later than Massachusetts
  • New Hampshire: arrives the second week of July, 3 weeks later than Massachusetts
  • Connecticut: arrives late July, 5 weeks later than Massachusetts
  • Vermont: arrives mid July, 4 weeks later than Massachusetts

Common questions

When do Bonaparte's Gulls arrive in Massachusetts?
Bonaparte's Gulls are winter birds in Massachusetts: they arrive in mid June, peak in early November (2.9% of checklists), and most are gone by the second week of January.
When do Bonaparte's Gulls leave Massachusetts?
Most Bonaparte's Gulls have left Massachusetts by the second week of January, when reports fall below half their usual rate.
When is the best time to see a Bonaparte's Gull in Massachusetts?
The Bonaparte's Gull is reported most often in early November, on about 2.9% of Massachusetts checklists.
Where in Massachusetts are Bonaparte's Gulls seen most often?
By county, Barnstable County, Nantucket County, and Dukes County have the highest peak reporting rates for the Bonaparte's Gull (counties with at least 200 checklists).