WhenToBird

Hydroprogne caspia · Laridae

When Do Caspian Terns Arrive in North Dakota?

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

Caspian Terns arrive in North Dakota in late April, peak in mid July (1.2% of checklists), and most are gone by mid September.

When to look

First arrivalsApr 22-30late April
Common byApr 22-30late April
PeakJul 15-21mid July
Most gone bySep 15-21mid September

Best: mid July. First arrivals late April; most are gone by mid September. Peak: on about 1.2% of North Dakota checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Apruncommon
  5. Maycommon
  6. Junpeak season
  7. Julpeak season
  8. Augpeak season
  9. Sepcommon
  10. Octuncommon
  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 1694 checklistsJan 8-14: 0% of 1210 checklistsJan 15-21: 0% of 1263 checklistsJan 22-31: 0% of 1984 checklistsFeb 1-7: 0% of 1209 checklistsFeb 8-14: 0% of 1307 checklistsFeb 15-21: 0% of 1655 checklistsFeb 22-28: 0% of 1619 checklistsMar 1-7: 0% of 1653 checklistsMar 8-14: 0% of 1818 checklistsMar 15-21: 0% of 2103 checklistsMar 22-31: 0% of 3714 checklistsApr 1-7: 0% of 2955 checklistsApr 8-14: 0% of 3550 checklistsApr 15-21: 0.1% of 4104 checklistsApr 22-30: 0.4% of 5712 checklistsMay 1-7: 0.8% of 5328 checklistsMay 8-14: 0.5% of 5885 checklistsMay 15-21: 0.9% of 5344 checklistsMay 22-31: 0.8% of 7512 checklistsJun 1-7: 0.7% of 4329 checklistsJun 8-14: 1.1% of 4287 checklistsJun 15-21: 1.0% of 3798 checklistsJun 22-30: 1.3% of 4361 checklistsJul 1-7: 0.9% of 2939 checklistsJul 8-14: 1.2% of 2407 checklistsJul 15-21: 1.5% of 2254 checklistsJul 22-31: 0.9% of 2852 checklistsAug 1-7: 1.1% of 2119 checklistsAug 8-14: 0.8% of 2044 checklistsAug 15-21: 0.7% of 2124 checklistsAug 22-31: 0.9% of 3168 checklistsSep 1-7: 0.6% of 2449 checklistsSep 8-14: 0.9% of 2310 checklistsSep 15-21: 0.6% of 2092 checklistsSep 22-30: 0.5% of 2565 checklistsOct 1-7: 0.1% of 2071 checklistsOct 8-14: 0% of 1918 checklistsOct 15-21: 0% of 1907 checklistsOct 22-31: 0% of 2589 checklistsNov 1-7: 0% of 1858 checklistsNov 8-14: 0% of 1753 checklistsNov 15-21: 0% of 1483 checklistsNov 22-30: 0% of 1928 checklistsDec 1-7: 0% of 1337 checklistsDec 8-14: 0% of 1309 checklistsDec 15-21: 0% of 1642 checklistsDec 22-31: 0% of 1830 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 North 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 North Dakota

Best counties

Share of checklists at the peak
  1. Mercer CountyBest late July · 30 checklists that week, 2,518 in all13%
  2. Nelson CountyBest late September · 14 checklists that week, 470 in all9.7%
  3. Kidder CountyBest late July · 106 checklists that week, 3,135 in all7.5%
  4. Benson CountyBest the second week of July · 36 checklists that week, 986 in all6.5%
  5. Oliver CountyBest late August · 23 checklists that week, 776 in all5.9%
  6. Dunn CountyBest early August · 30 checklists that week, 661 in all5.8%

Best spots

Share of checklists at the peak
  1. Nd State Lands - Surface OwnershipKidder County, best late June · 27 checklists that week, 226 in all10%
  2. Horsehead LakeKidder County, best mid June · 20 checklists that week, 148 in all8.2%
  3. Burleigh County Waterfowl Production AreaBurleigh County, best late June · 28 checklists that week, 493 in all6.8%
  4. BOR LandsStark County, best early May · 23 checklists that week, 357 in all6.3%
  5. General Sibley ParkBurleigh County, best early May · 30 checklists that week, 316 in all4.2%

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

Best time of day

In North Dakota, the Caspian Tern is most often listed on checklists started between 6 and 8 am (0.7% of those checklists).

0%0.5%1%12 am: too few checklists (74) to judge1 am: too few checklists (45) to judge2 am: too few checklists (42) to judge3 am: too few checklists (68) to judge4 am: too few checklists (274) to judge5 am: too few checklists (1538) to judge6 am: 0.9% of 4242 checklists7 am: 0.6% of 9520 checklists8 am: 0.4% of 13065 checklists9 am: 0.5% of 13356 checklists10 am: 0.4% of 12128 checklists11 am: 0.6% of 10772 checklists12 pm: 0.4% of 10316 checklists1 pm: 0.4% of 9169 checklists2 pm: 0.4% of 8880 checklists3 pm: 0.5% of 8688 checklists4 pm: 0.5% of 8201 checklists5 pm: 0.5% of 6687 checklists6 pm: 0.5% of 5455 checklists7 pm: 0.7% of 3926 checklists8 pm: too few checklists (2024) to judge9 pm: too few checklists (602) to judge10 pm: too few checklists (181) to judge11 pm: too few checklists (89) 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%0.1%0.4%
May0.8%0.5%0.9%0.8%
June0.7%1.1%1.0%1.3%
July0.9%1.2%1.5%0.9%
August1.1%0.8%0.7%0.9%
September0.6%0.9%0.6%0.5%
October0.1%0%0%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • South Dakota: arrives mid April, 1 week earlier than North Dakota
  • Minnesota: arrives late April, in the same week than North Dakota
  • Iowa: arrives late July, 12 weeks later than North Dakota
  • Wyoming: arrives mid April, 1 week earlier than North Dakota

Common questions

When do Caspian Terns arrive in North Dakota?
Caspian Terns arrive in North Dakota in late April, peak in mid July (1.2% of checklists), and most are gone by mid September.
When do Caspian Terns leave North Dakota?
Most Caspian Terns have left North Dakota by mid September, when reports fall below half their usual rate.
When is the best time to see a Caspian Tern in North Dakota?
The Caspian Tern is reported most often in mid July, on about 1.2% of North Dakota checklists.
Where in North Dakota are Caspian Terns seen most often?
By county, Mercer County, Nelson County, and Kidder County have the highest peak reporting rates for the Caspian Tern (counties with at least 200 checklists).