WhenToBird

Botaurus lentiginosus · Ardeidae

When Do American Bitterns Arrive in Washington?

Adult American Bittern
Photo: Kathy Richardson, CC BY 4.0 via iNaturalist

American Bitterns arrive in Washington in the second week of January, peak in late May (1.0% of checklists), and most are gone by early December.

When to look

First arrivalsJan 8-14the second week of January
Common byJan 8-14the second week of January
PeakMay 22-31late May
Most gone byDec 1-7early December

Best: late May. First arrivals the second week of January; most are gone by early December. Peak: on about 1.0% of Washington checklists.

  1. Januncommon
  2. Febuncommon
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Augcommon
  9. Sepcommon
  10. Octcommon
  11. Novcommon
  12. Decuncommon

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

0%0.5%1%1.5%Jan 1-7: 0.2% of 41928 checklistsJan 8-14: 0.2% of 31152 checklistsJan 15-21: 0.3% of 31753 checklistsJan 22-31: 0.3% of 42530 checklistsFeb 1-7: 0.3% of 29739 checklistsFeb 8-14: 0.2% of 32746 checklistsFeb 15-21: 0.3% of 40328 checklistsFeb 22-28: 0.3% of 28432 checklistsMar 1-7: 0.3% of 30758 checklistsMar 8-14: 0.4% of 29368 checklistsMar 15-21: 0.4% of 32580 checklistsMar 22-31: 0.5% of 45614 checklistsApr 1-7: 0.6% of 33997 checklistsApr 8-14: 0.7% of 34729 checklistsApr 15-21: 0.8% of 38474 checklistsApr 22-30: 0.8% of 52185 checklistsMay 1-7: 0.9% of 44236 checklistsMay 8-14: 0.9% of 48708 checklistsMay 15-21: 1.0% of 41742 checklistsMay 22-31: 1.0% of 57082 checklistsJun 1-7: 0.9% of 39193 checklistsJun 8-14: 0.8% of 36042 checklistsJun 15-21: 0.8% of 34003 checklistsJun 22-30: 0.6% of 39711 checklistsJul 1-7: 0.5% of 31949 checklistsJul 8-14: 0.4% of 29086 checklistsJul 15-21: 0.4% of 28045 checklistsJul 22-31: 0.5% of 38275 checklistsAug 1-7: 0.4% of 28846 checklistsAug 8-14: 0.5% of 28036 checklistsAug 15-21: 0.7% of 27614 checklistsAug 22-31: 0.7% of 40356 checklistsSep 1-7: 0.5% of 31214 checklistsSep 8-14: 0.5% of 27795 checklistsSep 15-21: 0.6% of 29677 checklistsSep 22-30: 0.5% of 35241 checklistsOct 1-7: 0.4% of 28605 checklistsOct 8-14: 0.4% of 28655 checklistsOct 15-21: 0.4% of 24643 checklistsOct 22-31: 0.4% of 34874 checklistsNov 1-7: 0.3% of 25658 checklistsNov 8-14: 0.4% of 25700 checklistsNov 15-21: 0.4% of 24331 checklistsNov 22-30: 0.4% of 32784 checklistsDec 1-7: 0.3% of 24099 checklistsDec 8-14: 0.3% of 23339 checklistsDec 15-21: 0.2% of 27666 checklistsDec 22-31: 0.2% of 42130 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 Washington 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 Washington

Best counties

Share of checklists at the peak
  1. Clark CountyBest late May · 1937 checklists that week, 53,250 in all12%
  2. Thurston CountyBest mid August · 1102 checklists that week, 68,352 in all4.0%
  3. Skagit CountyBest mid May · 1702 checklists that week, 78,154 in all2.5%
  4. Whatcom CountyBest the second week of April · 1375 checklists that week, 64,687 in all1.9%
  5. Yakima CountyBest late April · 1019 checklists that week, 28,504 in all1.8%
  6. Pacific CountyBest the second week of September · 476 checklists that week, 19,516 in all1.8%

Best spots

Share of checklists at the peak
  1. Buckmire SloughClark County, best late June · 21 checklists that week, 1,347 in all75%
  2. Northern State Recreation Area (southwest)Skagit County, best late April · 20 checklists that week, 503 in all74%
  3. Steigerwald Lake National Wildlife RefugeClark County, best the second week of May · 81 checklists that week, 2,714 in all55%
  4. Beaver LakeSkagit County, best the second week of June · 32 checklists that week, 176 in all46%
  5. StillwaterKing County, best mid April · 57 checklists that week, 1,710 in all45%

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

Best time of day

In Washington, the American Bittern is most often listed on checklists started between 5 and 7 pm (0.8% of those checklists).

0%0.5%1%1.5%12 am: too few checklists (796) to judge1 am: too few checklists (776) to judge2 am: too few checklists (709) to judge3 am: too few checklists (901) to judge4 am: too few checklists (3221) to judge5 am: too few checklists (16576) to judge6 am: 1.0% of 56744 checklists7 am: 0.7% of 133294 checklists8 am: 0.6% of 184196 checklists9 am: 0.5% of 186303 checklists10 am: 0.5% of 177063 checklists11 am: 0.4% of 154936 checklists12 pm: 0.4% of 138061 checklists1 pm: 0.4% of 127449 checklists2 pm: 0.4% of 121511 checklists3 pm: 0.5% of 107793 checklists4 pm: 0.5% of 82862 checklists5 pm: 0.7% of 57183 checklists6 pm: 0.9% of 39886 checklists7 pm: too few checklists (26969) to judge8 pm: too few checklists (12427) to judge9 pm: too few checklists (3658) to judge10 pm: too few checklists (1500) to judge11 pm: too few checklists (834) 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
January0.2%0.2%0.3%0.3%
February0.3%0.2%0.3%0.3%
March0.3%0.4%0.4%0.5%
April0.6%0.7%0.8%0.8%
May0.9%0.9%1.0%1.0%
June0.9%0.8%0.8%0.6%
July0.5%0.4%0.4%0.5%
August0.4%0.5%0.7%0.7%
September0.5%0.5%0.6%0.5%
October0.4%0.4%0.4%0.4%
November0.3%0.4%0.4%0.4%
December0.3%0.3%0.2%0.2%

Neighboring states

  • Oregon: arrives early April, 11 weeks later than Washington
  • North Dakota: arrives early May, 15 weeks later than Washington
  • South Dakota: arrives mid April, 13 weeks later than Washington
  • Kansas: arrives early April, 11 weeks later than Washington

Common questions

When do American Bitterns arrive in Washington?
American Bitterns arrive in Washington in the second week of January, peak in late May (1.0% of checklists), and most are gone by early December.
When do American Bitterns leave Washington?
Most American Bitterns have left Washington by early December, when reports fall below half their usual rate.
When is the best time to see a American Bittern in Washington?
The American Bittern is reported most often in late May, on about 1.0% of Washington checklists.
Where in Washington are American Bitterns seen most often?
By county, Clark County, Thurston County, and Skagit County have the highest peak reporting rates for the American Bittern (counties with at least 200 checklists).