WhenToBird

Chroicocephalus philadelphia · Laridae

When Do Bonaparte's Gulls Arrive in Alaska?

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

Bonaparte's Gulls reach Alaska in the second week of April, are common by mid April, peak in the second week of May (11% of checklists), and most are gone by mid October.

When to look

First arrivalsApr 8-14the second week of April
Common byApr 15-21mid April
PeakMay 8-14the second week of May
Most gone byOct 15-21mid October

Best: the second week of May. First arrivals the second week of April; most are gone by mid October. Peak: on about 11% of Alaska checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Sepcommon
  10. Octuncommon
  11. Novuncommon
  12. Decnot usually seen

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

0%5%10%15%Jan 1-7: 0.1% of 3788 checklistsJan 8-14: 0.1% of 2852 checklistsJan 15-21: 0% of 2810 checklistsJan 22-31: 0.1% of 3629 checklistsFeb 1-7: 0% of 2519 checklistsFeb 8-14: 0.1% of 2927 checklistsFeb 15-21: 0% of 3743 checklistsFeb 22-28: 0% of 2846 checklistsMar 1-7: 0% of 2904 checklistsMar 8-14: 0.1% of 3073 checklistsMar 15-21: 0.1% of 3359 checklistsMar 22-31: 0.1% of 5855 checklistsApr 1-7: 0.4% of 4329 checklistsApr 8-14: 1.2% of 4949 checklistsApr 15-21: 4.0% of 7114 checklistsApr 22-30: 8.5% of 10916 checklistsMay 1-7: 12% of 11827 checklistsMay 8-14: 11% of 14115 checklistsMay 15-21: 10% of 12152 checklistsMay 22-31: 7.2% of 19919 checklistsJun 1-7: 5.0% of 15816 checklistsJun 8-14: 4.2% of 17194 checklistsJun 15-21: 3.3% of 15943 checklistsJun 22-30: 4.3% of 16192 checklistsJul 1-7: 4.7% of 9815 checklistsJul 8-14: 6.4% of 8263 checklistsJul 15-21: 8.1% of 7081 checklistsJul 22-31: 9.8% of 9434 checklistsAug 1-7: 9.5% of 6380 checklistsAug 8-14: 9.1% of 6258 checklistsAug 15-21: 8.3% of 6114 checklistsAug 22-31: 7.6% of 8189 checklistsSep 1-7: 6.6% of 5848 checklistsSep 8-14: 5.6% of 4853 checklistsSep 15-21: 5.5% of 4415 checklistsSep 22-30: 4.5% of 5086 checklistsOct 1-7: 4.1% of 3576 checklistsOct 8-14: 3.7% of 4212 checklistsOct 15-21: 3.0% of 3339 checklistsOct 22-31: 3.3% of 4169 checklistsNov 1-7: 2.2% of 2844 checklistsNov 8-14: 1.5% of 2753 checklistsNov 15-21: 1.3% of 2291 checklistsNov 22-30: 0.5% of 3066 checklistsDec 1-7: 0.1% of 2199 checklistsDec 8-14: 0.1% of 2472 checklistsDec 15-21: 0.1% of 3071 checklistsDec 22-31: 0.1% of 3442 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 Alaska 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 Alaska

Best counties

Share of checklists at the peak
  1. Petersburg BoroughBest early August · 136 checklists that week, 6,063 in all42%
  2. Bristol Bay BoroughBest early August · 25 checklists that week, 980 in all34%
  3. Hoonah-Angoon Census AreaBest late September · 127 checklists that week, 8,159 in all29%
  4. Haines BoroughBest early May · 23 checklists that week, 1,690 in all28%
  5. Yakutat City and BoroughBest mid August · 14 checklists that week, 545 in all27%
  6. Ketchikan Gateway BoroughBest early August · 132 checklists that week, 4,641 in all26%

Best spots

Share of checklists at the peak
  1. Eagle RiverJuneau City and Borough, best early August · 41 checklists that week, 1,420 in all91%
  2. Viapan LakeKenai Peninsula Borough, best late May · 35 checklists that week, 153 in all90%
  3. Bootlegger CoveAnchorage Municipality, best mid July · 86 checklists that week, 2,460 in all79%
  4. Otter LakeAnchorage Municipality, best late May · 33 checklists that week, 143 in all75%

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

Best time of day

In Alaska, the Bonaparte's Gull is most often listed on checklists started between 6 and 8 am (7.5% of those checklists).

0%2%4%6%8%12 am: too few checklists (549) to judge1 am: too few checklists (365) to judge2 am: too few checklists (291) to judge3 am: too few checklists (624) to judge4 am: too few checklists (1241) to judge5 am: too few checklists (3532) to judge6 am: 7.6% of 9751 checklists7 am: 7.5% of 17236 checklists8 am: 6.1% of 24936 checklists9 am: 5.4% of 30139 checklists10 am: 5.0% of 30866 checklists11 am: 4.4% of 28207 checklists12 pm: 4.2% of 25650 checklists1 pm: 4.2% of 24144 checklists2 pm: 4.2% of 23323 checklists3 pm: 4.2% of 20763 checklists4 pm: 5.2% of 18245 checklists5 pm: 5.8% of 14895 checklists6 pm: 6.5% of 11707 checklists7 pm: 7.1% of 9365 checklists8 pm: 6.6% of 6934 checklists9 pm: too few checklists (4176) to judge10 pm: too few checklists (2050) to judge11 pm: too few checklists (952) 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%0.1%0%0.1%
February0%0.1%0%0%
March0%0.1%0.1%0.1%
April0.4%1.2%4.0%8.5%
May12%11%10%7.2%
June5.0%4.2%3.3%4.3%
July4.7%6.4%8.1%9.8%
August9.5%9.1%8.3%7.6%
September6.6%5.6%5.5%4.5%
October4.1%3.7%3.0%3.3%
November2.2%1.5%1.3%0.5%
December0.1%0.1%0.1%0.1%

Neighboring states

  • Washington: arrives mid July, 13 weeks later than Alaska
  • Oregon: arrives the second week of July, 12 weeks later than Alaska
  • Idaho: arrives early August, 15 weeks later than Alaska
  • Montana: arrives late July, 14 weeks later than Alaska

Common questions

When do Bonaparte's Gulls arrive in Alaska?
Bonaparte's Gulls reach Alaska in the second week of April, are common by mid April, peak in the second week of May (11% of checklists), and most are gone by mid October.
When do Bonaparte's Gulls leave Alaska?
Most Bonaparte's Gulls have left Alaska by mid October, when reports fall below half their usual rate. Stragglers are still reported until mid November.
When is the best time to see a Bonaparte's Gull in Alaska?
The Bonaparte's Gull is reported most often in the second week of May, on about 11% of Alaska checklists.
Where in Alaska are Bonaparte's Gulls seen most often?
By county, Petersburg Borough, Bristol Bay Borough, and Hoonah-Angoon Census Area have the highest peak reporting rates for the Bonaparte's Gull (counties with at least 200 checklists).