WhenToBird

Hydroprogne caspia · Laridae

When Do Caspian Terns Arrive in Washington?

Adult Caspian Tern
Photo: Daughter Dad, CC BY 4.0 via iNaturalist

Caspian Terns reach Washington in early April, are common by mid April, peak in late August (14% of checklists), and most are gone by late September.

When to look

First arrivalsApr 1-7early April
Common byApr 15-21mid April
PeakAug 22-31late August
Most gone bySep 22-30late September

Best: late August. First arrivals early April; most are gone by late September. Peak: on about 14% of Washington checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprcommon
  5. Maycommon
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octuncommon
  11. Novnot usually seen
  12. Decnot usually seen

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

0%5%10%15%Jan 1-7: 0.1% of 41928 checklistsJan 8-14: 0% of 31152 checklistsJan 15-21: 0% of 31753 checklistsJan 22-31: 0% of 42530 checklistsFeb 1-7: 0% of 29739 checklistsFeb 8-14: 0% of 32746 checklistsFeb 15-21: 0.1% of 40328 checklistsFeb 22-28: 0% of 28432 checklistsMar 1-7: 0% of 30758 checklistsMar 8-14: 0.1% of 29368 checklistsMar 15-21: 0.1% of 32580 checklistsMar 22-31: 0.2% of 45614 checklistsApr 1-7: 1.0% of 33997 checklistsApr 8-14: 2.6% of 34729 checklistsApr 15-21: 5.7% of 38474 checklistsApr 22-30: 8.5% of 52185 checklistsMay 1-7: 8.3% of 44236 checklistsMay 8-14: 7.1% of 48708 checklistsMay 15-21: 6.6% of 41742 checklistsMay 22-31: 7.0% of 57082 checklistsJun 1-7: 6.1% of 39193 checklistsJun 8-14: 6.6% of 36042 checklistsJun 15-21: 6.9% of 34003 checklistsJun 22-30: 8.1% of 39711 checklistsJul 1-7: 9.6% of 31949 checklistsJul 8-14: 9.7% of 29086 checklistsJul 15-21: 10% of 28045 checklistsJul 22-31: 12% of 38275 checklistsAug 1-7: 12% of 28846 checklistsAug 8-14: 13% of 28036 checklistsAug 15-21: 14% of 27614 checklistsAug 22-31: 14% of 40356 checklistsSep 1-7: 13% of 31214 checklistsSep 8-14: 12% of 27795 checklistsSep 15-21: 8.7% of 29677 checklistsSep 22-30: 5.3% of 35241 checklistsOct 1-7: 2.6% of 28605 checklistsOct 8-14: 1.0% of 28655 checklistsOct 15-21: 0.5% of 24643 checklistsOct 22-31: 0.2% of 34874 checklistsNov 1-7: 0.1% of 25658 checklistsNov 8-14: 0.1% of 25700 checklistsNov 15-21: 0.1% of 24331 checklistsNov 22-30: 0.1% of 32784 checklistsDec 1-7: 0.1% of 24099 checklistsDec 8-14: 0.1% of 23339 checklistsDec 15-21: 0.1% of 27666 checklistsDec 22-31: 0.1% 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. Pacific CountyBest mid August · 450 checklists that week, 19,516 in all45%
  2. Grays Harbor CountyBest mid August · 907 checklists that week, 28,443 in all40%
  3. Wahkiakum CountyBest early September · 93 checklists that week, 5,618 in all31%
  4. Kitsap CountyBest the second week of August · 1196 checklists that week, 74,545 in all26%
  5. Benton CountyBest mid July · 396 checklists that week, 23,565 in all26%
  6. Pierce CountyBest early September · 1732 checklists that week, 92,224 in all22%

Best spots

Share of checklists at the peak
  1. Puyallup WaterwayPierce County, best the second week of August · 21 checklists that week, 489 in all99%
  2. Mcnary National Wildlife Refuge (Hunt)Walla Walla County, best late April · 36 checklists that week, 1,089 in all98%
  3. Haapoos Village Park and Shoreline HabitatKing County, best late April · 23 checklists that week, 750 in all95%
  4. Dune Peninsula at Point Defiance ParkPierce County, best mid August · 119 checklists that week, 4,257 in all94%
  5. Jetty Island Nature PreserveSnohomish County, best the second week of August · 49 checklists that week, 356 in all93%

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

Best time of day

In Washington, the Caspian Tern is most often listed on checklists started between 6 and 8 am (7.6% of those checklists).

0%5%10%15%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: 11% of 56744 checklists7 am: 6.0% of 133294 checklists8 am: 4.4% of 184196 checklists9 am: 4.3% of 186303 checklists10 am: 4.0% of 177063 checklists11 am: 3.8% of 154936 checklists12 pm: 3.4% of 138061 checklists1 pm: 3.7% of 127449 checklists2 pm: 3.6% of 121511 checklists3 pm: 3.8% of 107793 checklists4 pm: 4.6% of 82862 checklists5 pm: 5.4% of 57183 checklists6 pm: 5.7% 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
January0.1%0%0%0%
February0%0%0.1%0%
March0%0.1%0.1%0.2%
April1.0%2.6%5.7%8.5%
May8.3%7.1%6.6%7.0%
June6.1%6.6%6.9%8.1%
July9.6%9.7%10%12%
August12%13%14%14%
September13%12%8.7%5.3%
October2.6%1.0%0.5%0.2%
November0.1%0.1%0.1%0.1%
December0.1%0.1%0.1%0.1%

Neighboring states

  • Oregon: arrives the second week of April, 1 week later than Washington
  • Idaho: arrives mid April, 2 weeks later than Washington
  • Montana: arrives mid April, 2 weeks later than Washington
  • Nevada: arrives the second week of April, 1 week later than Washington

Common questions

When do Caspian Terns arrive in Washington?
Caspian Terns reach Washington in early April, are common by mid April, peak in late August (14% of checklists), and most are gone by late September.
When do Caspian Terns leave Washington?
Most Caspian Terns have left Washington by late September, when reports fall below half their usual rate. Stragglers are still reported until the second week of October.
When is the best time to see a Caspian Tern in Washington?
The Caspian Tern is reported most often in late August, on about 14% of Washington checklists.
Where in Washington are Caspian Terns seen most often?
By county, Pacific County, Grays Harbor County, and Wahkiakum County have the highest peak reporting rates for the Caspian Tern (counties with at least 200 checklists).