WhenToBird

Sternula antillarum · Laridae

When Do Least Terns Arrive in Oklahoma?

Adult Least Tern
Photo: datadan, CC BY 4.0 via iNaturalist

Least Terns reach Oklahoma in the second week of May, are common by mid May, peak in early August (4.5% of checklists), and most are gone by late August.

When to look

First arrivalsMay 8-14the second week of May
Common byMay 15-21mid May
PeakAug 1-7early August
Most gone byAug 22-31late August

Best: early August. First arrivals the second week of May; most are gone by late August. Peak: on about 4.5% of Oklahoma checklists.

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

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

0%2%4%6%Jan 1-7: 0% of 6087 checklistsJan 8-14: 0% of 4350 checklistsJan 15-21: 0% of 4381 checklistsJan 22-31: 0% of 6165 checklistsFeb 1-7: 0% of 4259 checklistsFeb 8-14: 0% of 4589 checklistsFeb 15-21: 0% of 7001 checklistsFeb 22-28: 0% of 4482 checklistsMar 1-7: 0% of 4724 checklistsMar 8-14: 0% of 4571 checklistsMar 15-21: 0% of 4393 checklistsMar 22-31: 0% of 7544 checklistsApr 1-7: 0% of 5967 checklistsApr 8-14: 0.1% of 6543 checklistsApr 15-21: 0% of 7366 checklistsApr 22-30: 0.1% of 10618 checklistsMay 1-7: 0.4% of 8835 checklistsMay 8-14: 1.4% of 8247 checklistsMay 15-21: 2.4% of 6081 checklistsMay 22-31: 3.2% of 7283 checklistsJun 1-7: 2.5% of 4256 checklistsJun 8-14: 1.9% of 3774 checklistsJun 15-21: 2.4% of 3541 checklistsJun 22-30: 2.3% of 4159 checklistsJul 1-7: 2.2% of 3209 checklistsJul 8-14: 3.2% of 2916 checklistsJul 15-21: 3.5% of 2861 checklistsJul 22-31: 5.1% of 4146 checklistsAug 1-7: 4.1% of 3043 checklistsAug 8-14: 3.9% of 2839 checklistsAug 15-21: 3.8% of 3014 checklistsAug 22-31: 1.4% of 4759 checklistsSep 1-7: 0.6% of 3861 checklistsSep 8-14: 0.5% of 3748 checklistsSep 15-21: 0.1% of 3569 checklistsSep 22-30: 0% of 4830 checklistsOct 1-7: 0% of 3809 checklistsOct 8-14: 0.1% of 4142 checklistsOct 15-21: 0% of 3705 checklistsOct 22-31: 0% of 4738 checklistsNov 1-7: 0% of 3823 checklistsNov 8-14: 0% of 3849 checklistsNov 15-21: 0% of 3722 checklistsNov 22-30: 0% of 4795 checklistsDec 1-7: 0% of 3324 checklistsDec 8-14: 0% of 3574 checklistsDec 15-21: 0% of 3884 checklistsDec 22-31: 0% of 5774 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 Oklahoma 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 Oklahoma

Best counties

Share of checklists at the peak
  1. Alfalfa CountyBest early June · 44 checklists that week, 3,843 in all25%
  2. Sequoyah CountyBest late June · 17 checklists that week, 1,522 in all15%
  3. Tulsa CountyBest mid July · 410 checklists that week, 33,355 in all15%
  4. Bryan CountyBest mid May · 25 checklists that week, 1,517 in all11%
  5. Cotton CountyBest late June · 11 checklists that week, 765 in all9.5%
  6. Oklahoma CountyBest early August · 584 checklists that week, 38,139 in all8.7%

Best spots

Share of checklists at the peak
  1. Lake Hefner (NW Oklahoma City Sludge Lagoon)Oklahoma County, best late July · 34 checklists that week, 295 in all95%
  2. Lake YaholaTulsa County, best late July · 41 checklists that week, 1,291 in all88%
  3. Salt Plains National Wildlife RefugeAlfalfa County, best late May · 24 checklists that week, 407 in all60%
  4. Lake Hefner (southeast)Oklahoma County, best late July · 25 checklists that week, 612 in all57%
  5. Washington Irving ParkTulsa County, best late May · 20 checklists that week, 449 in all42%
  6. Lake Hefner (Lansbrook Lake)Oklahoma County, best early August · 27 checklists that week, 743 in all39%

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

Best time of day

In Oklahoma, the Least Tern is most often listed on checklists started between 6 and 8 am (1.2% of those checklists).

0%1%2%3%12 am: too few checklists (91) to judge1 am: too few checklists (65) to judge2 am: too few checklists (73) to judge3 am: too few checklists (73) to judge4 am: too few checklists (100) to judge5 am: too few checklists (647) to judge6 am: 2.3% of 8353 checklists7 am: 0.8% of 24509 checklists8 am: 1.0% of 27848 checklists9 am: 0.8% of 25316 checklists10 am: 0.7% of 21161 checklists11 am: 0.6% of 18730 checklists12 pm: 0.6% of 16097 checklists1 pm: 0.7% of 14028 checklists2 pm: 0.8% of 13599 checklists3 pm: 0.7% of 14228 checklists4 pm: 0.6% of 14597 checklists5 pm: 0.6% of 12125 checklists6 pm: 0.8% of 9337 checklists7 pm: 1.0% of 6944 checklists8 pm: too few checklists (2403) to judge9 pm: too few checklists (459) to judge10 pm: too few checklists (226) to judge11 pm: too few checklists (141) 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%0%0%0%
February0%0%0%0%
March0%0%0%0%
April0%0.1%0%0.1%
May0.4%1.4%2.4%3.2%
June2.5%1.9%2.4%2.3%
July2.2%3.2%3.5%5.1%
August4.1%3.9%3.8%1.4%
September0.6%0.5%0.1%0%
October0%0.1%0%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Arkansas: arrives mid May, 1 week later than Oklahoma
  • Missouri: arrives mid May, 1 week later than Oklahoma
  • Nebraska: arrives mid May, 1 week later than Oklahoma
  • Texas: arrives early April, 5 weeks earlier than Oklahoma

Common questions

When do Least Terns arrive in Oklahoma?
Least Terns reach Oklahoma in the second week of May, are common by mid May, peak in early August (4.5% of checklists), and most are gone by late August.
When do Least Terns leave Oklahoma?
Most Least Terns have left Oklahoma by late August, when reports fall below half their usual rate.
When is the best time to see a Least Tern in Oklahoma?
The Least Tern is reported most often in early August, on about 4.5% of Oklahoma checklists.
Where in Oklahoma are Least Terns seen most often?
By county, Alfalfa County, Sequoyah County, and Tulsa County have the highest peak reporting rates for the Least Tern (counties with at least 200 checklists).