WhenToBird

Sternula antillarum · Laridae

When Do Least Terns Arrive in South Dakota?

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

Least Terns arrive in South Dakota in mid May, peak in early August (1.6% of checklists), and most are gone by mid August.

When to look

First arrivalsMay 15-21mid May
Common byMay 15-21mid May
PeakAug 1-7early August
Most gone byAug 15-21mid August

Best: early August. First arrivals mid May; most are gone by mid August. Peak: on about 1.6% of South Dakota 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. Seprare
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%0.5%1%1.5%2%Jan 1-7: 0% of 1699 checklistsJan 8-14: 0% of 967 checklistsJan 15-21: 0% of 893 checklistsJan 22-31: 0% of 1338 checklistsFeb 1-7: 0% of 898 checklistsFeb 8-14: 0% of 1013 checklistsFeb 15-21: 0% of 1650 checklistsFeb 22-28: 0% of 1011 checklistsMar 1-7: 0% of 1304 checklistsMar 8-14: 0% of 1447 checklistsMar 15-21: 0% of 1524 checklistsMar 22-31: 0% of 2850 checklistsApr 1-7: 0% of 2170 checklistsApr 8-14: 0% of 2259 checklistsApr 15-21: 0% of 2578 checklistsApr 22-30: 0% of 3858 checklistsMay 1-7: 0.1% of 3532 checklistsMay 8-14: 0.1% of 4498 checklistsMay 15-21: 0.7% of 4211 checklistsMay 22-31: 1.4% of 5094 checklistsJun 1-7: 1.2% of 3279 checklistsJun 8-14: 0.8% of 3503 checklistsJun 15-21: 1.3% of 2861 checklistsJun 22-30: 1.0% of 3893 checklistsJul 1-7: 1.1% of 2666 checklistsJul 8-14: 1.2% of 2554 checklistsJul 15-21: 1.2% of 2412 checklistsJul 22-31: 1.7% of 2746 checklistsAug 1-7: 1.5% of 1842 checklistsAug 8-14: 1.5% of 1899 checklistsAug 15-21: 0.4% of 1757 checklistsAug 22-31: 0.5% of 2464 checklistsSep 1-7: 0% of 1894 checklistsSep 8-14: 0% of 1794 checklistsSep 15-21: 0% of 1671 checklistsSep 22-30: 0% of 2085 checklistsOct 1-7: 0% of 1429 checklistsOct 8-14: 0% of 1441 checklistsOct 15-21: 0% of 1330 checklistsOct 22-31: 0% of 1471 checklistsNov 1-7: 0% of 1168 checklistsNov 8-14: 0% of 1068 checklistsNov 15-21: 0% of 985 checklistsNov 22-30: 0% of 1108 checklistsDec 1-7: 0% of 890 checklistsDec 8-14: 0% of 957 checklistsDec 15-21: 0% of 1246 checklistsDec 22-31: 0% of 1514 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 South Dakota 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 South Dakota

Best counties

Share of checklists at the peak
  1. Clay CountyBest the second week of June · 49 checklists that week, 2,633 in all34%
  2. Gregory CountyBest the second week of July · 11 checklists that week, 472 in all17%
  3. Charles Mix CountyBest mid July · 61 checklists that week, 2,198 in all15%
  4. Yankton CountyBest early August · 43 checklists that week, 3,895 in all14%
  5. Union CountyBest early August · 16 checklists that week, 882 in all11%
  6. Sully CountyBest early June · 16 checklists that week, 632 in all10%

Best spots

Share of checklists at the peak
  1. Yankton UnitYankton County, best early June · 20 checklists that week, 760 in all21%
  2. Cotton ParkClay County, best late May · 20 checklists that week, 223 in all9.1%
  3. Oahe Downstream Recreation AreaStanley County, best mid May · 30 checklists that week, 509 in all5.9%

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

Best time of day

In South Dakota, the Least Tern is most often listed on checklists started between 6 and 8 am (1.0% of those checklists).

0%0.5%1%1.5%12 am: too few checklists (49) to judge1 am: too few checklists (44) to judge2 am: too few checklists (33) to judge3 am: too few checklists (59) to judge4 am: too few checklists (227) to judge5 am: too few checklists (1080) to judge6 am: 0.8% of 3387 checklists7 am: 1.0% of 7718 checklists8 am: 0.9% of 10342 checklists9 am: 0.6% of 10758 checklists10 am: 0.4% of 9123 checklists11 am: 0.3% of 7814 checklists12 pm: 0.4% of 6876 checklists1 pm: 0.4% of 6801 checklists2 pm: 0.3% of 6673 checklists3 pm: 0.4% of 6344 checklists4 pm: 0.2% of 6412 checklists5 pm: 0.3% of 5570 checklists6 pm: 0.3% of 4276 checklists7 pm: 0.4% of 3183 checklists8 pm: too few checklists (1499) to judge9 pm: too few checklists (329) to judge10 pm: too few checklists (82) to judge11 pm: too few checklists (42) 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%0%0%
May0.1%0.1%0.7%1.4%
June1.2%0.8%1.3%1.0%
July1.1%1.2%1.2%1.7%
August1.5%1.5%0.4%0.5%
September0%0%0%0%
October0%0%0%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Nebraska: arrives mid May, in the same week than South Dakota
  • North Dakota: arrives late May, 1 week later than South Dakota
  • Missouri: arrives mid May, in the same week than South Dakota
  • Oklahoma: arrives the second week of May, 1 week earlier than South Dakota

Common questions

When do Least Terns arrive in South Dakota?
Least Terns arrive in South Dakota in mid May, peak in early August (1.6% of checklists), and most are gone by mid August.
When do Least Terns leave South Dakota?
Most Least Terns have left South Dakota by mid August, when reports fall below half their usual rate.
When is the best time to see a Least Tern in South Dakota?
The Least Tern is reported most often in early August, on about 1.6% of South Dakota checklists.
Where in South Dakota are Least Terns seen most often?
By county, Clay County, Gregory County, and Charles Mix County have the highest peak reporting rates for the Least Tern (counties with at least 200 checklists).