WhenToBird

Chroicocephalus philadelphia · Laridae

When Do Bonaparte's Gulls Arrive in Maryland?

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

Bonaparte's Gulls arrive in Maryland in late October, peak in early April (5.3% of checklists), and most are gone by early May.

When to look

First arrivalsOct 22-31late October
Common byOct 22-31late October
PeakApr 1-7early April
Most gone byMay 1-7early May

Best: early April. First arrivals late October; most are gone by early May. Peak: on about 5.3% of Maryland checklists.

  1. Januncommon
  2. Febuncommon
  3. Marpeak season
  4. Aprpeak season
  5. Mayuncommon
  6. Junnot usually seen
  7. Julnot usually seen
  8. Augnot usually seen
  9. Sepnot usually seen
  10. Octuncommon
  11. Novcommon
  12. Decuncommon

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

0%2%4%6%8%Jan 1-7: 0.8% of 28716 checklistsJan 8-14: 0.9% of 21449 checklistsJan 15-21: 1.0% of 21267 checklistsJan 22-31: 0.8% of 29144 checklistsFeb 1-7: 1.0% of 21347 checklistsFeb 8-14: 0.7% of 22166 checklistsFeb 15-21: 0.6% of 29986 checklistsFeb 22-28: 1.0% of 22427 checklistsMar 1-7: 1.5% of 21389 checklistsMar 8-14: 2.2% of 22192 checklistsMar 15-21: 3.3% of 22823 checklistsMar 22-31: 4.9% of 33720 checklistsApr 1-7: 6.2% of 25513 checklistsApr 8-14: 4.7% of 27718 checklistsApr 15-21: 2.9% of 29328 checklistsApr 22-30: 1.2% of 42595 checklistsMay 1-7: 0.7% of 38532 checklistsMay 8-14: 0.5% of 42722 checklistsMay 15-21: 0.3% of 31936 checklistsMay 22-31: 0.1% of 36903 checklistsJun 1-7: 0.1% of 23191 checklistsJun 8-14: 0.1% of 21853 checklistsJun 15-21: 0.1% of 21000 checklistsJun 22-30: 0.1% of 25133 checklistsJul 1-7: 0.1% of 18715 checklistsJul 8-14: 0.1% of 16376 checklistsJul 15-21: 0.1% of 15793 checklistsJul 22-31: 0.1% of 21969 checklistsAug 1-7: 0.1% of 16013 checklistsAug 8-14: 0.2% of 15249 checklistsAug 15-21: 0.1% of 15674 checklistsAug 22-31: 0.1% of 24925 checklistsSep 1-7: 0.1% of 19808 checklistsSep 8-14: 0.1% of 18513 checklistsSep 15-21: 0.1% of 21901 checklistsSep 22-30: 0.1% of 22901 checklistsOct 1-7: 0.1% of 19111 checklistsOct 8-14: 0.2% of 18482 checklistsOct 15-21: 0.5% of 17380 checklistsOct 22-31: 0.7% of 23992 checklistsNov 1-7: 1.5% of 17915 checklistsNov 8-14: 2.8% of 18905 checklistsNov 15-21: 2.3% of 16259 checklistsNov 22-30: 1.8% of 22852 checklistsDec 1-7: 1.2% of 16108 checklistsDec 8-14: 1.3% of 16512 checklistsDec 15-21: 1.1% of 18952 checklistsDec 22-31: 1.3% of 29728 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 Maryland 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 Maryland

Best counties

Share of checklists at the peak
  1. Queen Anne's CountyBest early April · 549 checklists that week, 26,875 in all19%
  2. Kent CountyBest early April · 231 checklists that week, 13,396 in all17%
  3. Cecil CountyBest late March · 640 checklists that week, 18,620 in all13%
  4. Harford CountyBest late March · 1406 checklists that week, 39,311 in all12%
  5. Calvert CountyBest early April · 1070 checklists that week, 43,807 in all10%
  6. Worcester CountyBest late January · 1042 checklists that week, 44,596 in all9.8%

Best spots

Share of checklists at the peak
  1. Back RiverBaltimore County, best late March · 24 checklists that week, 139 in all99%
  2. Marina ParkCecil County, best late March · 32 checklists that week, 135 in all94%
  3. Coxs Point ParkBaltimore County, best the second week of April · 44 checklists that week, 599 in all91%
  4. Susquehanna SpHarford County, best mid March · 49 checklists that week, 693 in all90%
  5. Port DepositCecil County, best late March · 25 checklists that week, 102 in all89%

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

Best time of day

In Maryland, the Bonaparte's Gull is most often listed on checklists started between 6 and 8 am (1.3% of those checklists).

0%0.5%1%1.5%2%12 am: too few checklists (486) to judge1 am: too few checklists (451) to judge2 am: too few checklists (447) to judge3 am: too few checklists (766) to judge4 am: too few checklists (2076) to judge5 am: too few checklists (11098) to judge6 am: 1.6% of 56604 checklists7 am: 1.1% of 139255 checklists8 am: 1.0% of 148626 checklists9 am: 1.1% of 126820 checklists10 am: 1.2% of 106973 checklists11 am: 1.3% of 87483 checklists12 pm: 1.3% of 74808 checklists1 pm: 1.2% of 69428 checklists2 pm: 1.3% of 67800 checklists3 pm: 1.2% of 67688 checklists4 pm: 1.2% of 60927 checklists5 pm: 1.0% of 43876 checklists6 pm: 1.0% of 32930 checklists7 pm: too few checklists (19051) to judge8 pm: too few checklists (5708) to judge9 pm: too few checklists (1977) to judge10 pm: too few checklists (1170) to judge11 pm: too few checklists (635) 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%0.9%1.0%0.8%
February1.0%0.7%0.6%1.0%
March1.5%2.2%3.3%4.9%
April6.2%4.7%2.9%1.2%
May0.7%0.5%0.3%0.1%
June0.1%0.1%0.1%0.1%
July0.1%0.1%0.1%0.1%
August0.1%0.2%0.1%0.1%
September0.1%0.1%0.1%0.1%
October0.1%0.2%0.5%0.7%
November1.5%2.8%2.3%1.8%
December1.2%1.3%1.1%1.3%

Neighboring states

  • District of Columbia: arrives mid March, 19 weeks later than Maryland
  • Delaware: arrives early November, 1 week later than Maryland
  • Virginia: arrives early November, 1 week later than Maryland
  • Pennsylvania: arrives the second week of March, 18 weeks later than Maryland

Common questions

When do Bonaparte's Gulls arrive in Maryland?
Bonaparte's Gulls arrive in Maryland in late October, peak in early April (5.3% of checklists), and most are gone by early May.
When do Bonaparte's Gulls leave Maryland?
Most Bonaparte's Gulls have left Maryland by early May, when reports fall below half their usual rate.
When is the best time to see a Bonaparte's Gull in Maryland?
The Bonaparte's Gull is reported most often in early April, on about 5.3% of Maryland checklists.
Where in Maryland are Bonaparte's Gulls seen most often?
By county, Queen Anne's County, Kent County, and Cecil County have the highest peak reporting rates for the Bonaparte's Gull (counties with at least 200 checklists).