WhenToBird

Chroicocephalus philadelphia · Laridae

When Do Bonaparte's Gulls Arrive in Connecticut?

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

Bonaparte's Gulls are winter birds in Connecticut: they arrive in late July, peak in late March (1.2% of checklists), and most are gone by early May.

When to look

First arrivalsJul 22-31late July
Common byJul 22-31late July
PeakMar 22-31late March
Most gone byMay 1-7early May

Best: late March. First arrivals late July; most are gone by early May. Peak: on about 1.2% of Connecticut checklists.

  1. Januncommon
  2. Febuncommon
  3. Marpeak season
  4. Aprpeak season
  5. Mayrare
  6. Junrare
  7. Julrare
  8. Auguncommon
  9. Sepuncommon
  10. Octcommon
  11. Novcommon
  12. Decuncommon

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

0%0.5%1%1.5%Jan 1-7: 0.1% of 18950 checklistsJan 8-14: 0.4% of 13676 checklistsJan 15-21: 0.2% of 13377 checklistsJan 22-31: 0.2% of 17004 checklistsFeb 1-7: 0.1% of 10218 checklistsFeb 8-14: 0.2% of 11568 checklistsFeb 15-21: 0.2% of 15916 checklistsFeb 22-28: 0.5% of 11413 checklistsMar 1-7: 0.7% of 10754 checklistsMar 8-14: 0.8% of 12051 checklistsMar 15-21: 0.9% of 12616 checklistsMar 22-31: 1.2% of 17801 checklistsApr 1-7: 1.4% of 13186 checklistsApr 8-14: 0.8% of 14428 checklistsApr 15-21: 0.4% of 14738 checklistsApr 22-30: 0.2% of 21753 checklistsMay 1-7: 0.2% of 22494 checklistsMay 8-14: 0.1% of 23363 checklistsMay 15-21: 0.1% of 20219 checklistsMay 22-31: 0.2% of 20778 checklistsJun 1-7: 0.1% of 12234 checklistsJun 8-14: 0.1% of 12491 checklistsJun 15-21: 0.1% of 10856 checklistsJun 22-30: 0.1% of 11964 checklistsJul 1-7: 0.1% of 9437 checklistsJul 8-14: 0.1% of 8599 checklistsJul 15-21: 0.1% of 8252 checklistsJul 22-31: 0.2% of 11329 checklistsAug 1-7: 0.1% of 8116 checklistsAug 8-14: 0.2% of 8051 checklistsAug 15-21: 0.3% of 8502 checklistsAug 22-31: 0.4% of 13673 checklistsSep 1-7: 0.3% of 9873 checklistsSep 8-14: 0.2% of 9735 checklistsSep 15-21: 0.2% of 10120 checklistsSep 22-30: 0.2% of 12543 checklistsOct 1-7: 0.1% of 10735 checklistsOct 8-14: 0.3% of 10869 checklistsOct 15-21: 0.6% of 10436 checklistsOct 22-31: 0.6% of 13808 checklistsNov 1-7: 0.5% of 10507 checklistsNov 8-14: 0.5% of 9827 checklistsNov 15-21: 0.4% of 9904 checklistsNov 22-30: 0.2% of 13396 checklistsDec 1-7: 0.2% of 8974 checklistsDec 8-14: 0.1% of 9468 checklistsDec 15-21: 0.3% of 11614 checklistsDec 22-31: 0.2% of 16616 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 Connecticut 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 Connecticut

Best counties

Share of checklists at the peak
  1. Fairfield CountyBest early April · 3164 checklists that week, 139,848 in all2.9%
  2. New Haven CountyBest the second week of March · 2424 checklists that week, 139,721 in all2.5%
  3. New London CountyBest mid December · 1243 checklists that week, 65,205 in all0.9%
  4. Litchfield CountyBest the second week of April · 1705 checklists that week, 69,766 in all0.8%
  5. Tolland CountyBest the second week of November · 715 checklists that week, 39,004 in all0.4%
  6. Middlesex CountyBest late November · 828 checklists that week, 39,919 in all0.3%

Best spots

Share of checklists at the peak
  1. Southport BeachFairfield County, best early April · 69 checklists that week, 848 in all67%
  2. Sasco Hill BeachFairfield County, best mid October · 23 checklists that week, 136 in all59%
  3. Oyster River BeachNew Haven County, best early April · 33 checklists that week, 273 in all47%
  4. Greenwich HarborFairfield County, best early April · 23 checklists that week, 859 in all34%
  5. Hammonasset Natural Area PreserveNew Haven County, best the second week of March · 171 checklists that week, 10,098 in all22%
  6. Hammonasset Natural Area Preserve (Hammonasset Point)New Haven County, best the second week of March · 27 checklists that week, 1,736 in all22%

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

Best time of day

In Connecticut, the Bonaparte's Gull is most often listed on checklists started between 11 am and 1 pm (0.4% of those checklists).

0%0.5%12 am: too few checklists (325) to judge1 am: too few checklists (367) to judge2 am: too few checklists (488) to judge3 am: too few checklists (792) to judge4 am: too few checklists (2722) to judge5 am: too few checklists (9489) to judge6 am: 0.3% of 33657 checklists7 am: 0.2% of 62964 checklists8 am: 0.3% of 70645 checklists9 am: 0.3% of 64870 checklists10 am: 0.3% of 58827 checklists11 am: 0.4% of 51689 checklists12 pm: 0.4% of 45288 checklists1 pm: 0.4% of 44765 checklists2 pm: 0.4% of 44173 checklists3 pm: 0.4% of 41979 checklists4 pm: 0.3% of 33219 checklists5 pm: 0.3% of 24828 checklists6 pm: 0.1% of 15856 checklists7 pm: too few checklists (8126) to judge8 pm: too few checklists (1994) to judge9 pm: too few checklists (533) to judge10 pm: too few checklists (349) to judge11 pm: too few checklists (286) 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
January0.1%0.4%0.2%0.2%
February0.1%0.2%0.2%0.5%
March0.7%0.8%0.9%1.2%
April1.4%0.8%0.4%0.2%
May0.2%0.1%0.1%0.2%
June0.1%0.1%0.1%0.1%
July0.1%0.1%0.1%0.2%
August0.1%0.2%0.3%0.4%
September0.3%0.2%0.2%0.2%
October0.1%0.3%0.6%0.6%
November0.5%0.5%0.4%0.2%
December0.2%0.1%0.3%0.2%

Neighboring states

  • Rhode Island: arrives the second week of October, 10 weeks later than Connecticut
  • Massachusetts: arrives mid June, 5 weeks earlier than Connecticut
  • New Jersey: arrives late February, 20 weeks earlier than Connecticut
  • New York: arrives late July, in the same week than Connecticut

Common questions

When do Bonaparte's Gulls arrive in Connecticut?
Bonaparte's Gulls are winter birds in Connecticut: they arrive in late July, peak in late March (1.2% of checklists), and most are gone by early May.
When do Bonaparte's Gulls leave Connecticut?
Most Bonaparte's Gulls have left Connecticut by early May, when reports fall below half their usual rate.
When is the best time to see a Bonaparte's Gull in Connecticut?
The Bonaparte's Gull is reported most often in late March, on about 1.2% of Connecticut checklists.
Where in Connecticut are Bonaparte's Gulls seen most often?
By county, Fairfield County, New Haven County, and New London County have the highest peak reporting rates for the Bonaparte's Gull (counties with at least 200 checklists).