WhenToBird

Molothrus ater · Icteridae

When Do Brown-headed Cowbirds Arrive in South Dakota?

Adult female Brown-headed Cowbird
Photo: Nicole, CC BY 4.0 via iNaturalist

Brown-headed Cowbirds reach South Dakota in early April, are common by mid April, peak in mid May (36% of checklists), and most are gone by mid July.

When to look

First arrivalsApr 1-7early April
Common byApr 15-21mid April
PeakMay 15-21mid May
Most gone byJul 15-21mid July

Best: mid May. First arrivals early April; most are gone by mid July. Peak: on about 36% of South Dakota checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marrare
  4. Aprcommon
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Seprare
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%10%20%30%40%Jan 1-7: 0.4% of 1699 checklistsJan 8-14: 0.1% of 967 checklistsJan 15-21: 0.1% of 893 checklistsJan 22-31: 0.1% of 1338 checklistsFeb 1-7: 0% of 898 checklistsFeb 8-14: 0.2% of 1013 checklistsFeb 15-21: 0.3% of 1650 checklistsFeb 22-28: 0.2% of 1011 checklistsMar 1-7: 0.5% of 1304 checklistsMar 8-14: 0.6% of 1447 checklistsMar 15-21: 1.5% of 1524 checklistsMar 22-31: 1.5% of 2850 checklistsApr 1-7: 3.5% of 2170 checklistsApr 8-14: 8.7% of 2259 checklistsApr 15-21: 12% of 2578 checklistsApr 22-30: 20% of 3858 checklistsMay 1-7: 33% of 3532 checklistsMay 8-14: 35% of 4498 checklistsMay 15-21: 38% of 4211 checklistsMay 22-31: 35% of 5094 checklistsJun 1-7: 32% of 3279 checklistsJun 8-14: 30% of 3503 checklistsJun 15-21: 27% of 2861 checklistsJun 22-30: 27% of 3893 checklistsJul 1-7: 27% of 2666 checklistsJul 8-14: 23% of 2554 checklistsJul 15-21: 15% of 2412 checklistsJul 22-31: 10% of 2746 checklistsAug 1-7: 6.7% of 1842 checklistsAug 8-14: 5.1% of 1899 checklistsAug 15-21: 3.2% of 1757 checklistsAug 22-31: 2.5% of 2464 checklistsSep 1-7: 1.6% of 1894 checklistsSep 8-14: 1.6% of 1794 checklistsSep 15-21: 1.3% of 1671 checklistsSep 22-30: 1.1% of 2085 checklistsOct 1-7: 1.0% of 1429 checklistsOct 8-14: 1.3% of 1441 checklistsOct 15-21: 0.9% of 1330 checklistsOct 22-31: 0.6% of 1471 checklistsNov 1-7: 0.6% of 1168 checklistsNov 8-14: 0.4% of 1068 checklistsNov 15-21: 0.2% of 985 checklistsNov 22-30: 0.1% of 1108 checklistsDec 1-7: 0.1% of 890 checklistsDec 8-14: 0.1% of 957 checklistsDec 15-21: 0.2% of 1246 checklistsDec 22-31: 0.4% 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. Haakon CountyBest the second week of June · 26 checklists that week, 214 in all74%
  2. Jones CountyBest the second week of June · 34 checklists that week, 425 in all71%
  3. Campbell CountyBest early July · 18 checklists that week, 212 in all68%
  4. Hand CountyBest early July · 10 checklists that week, 388 in all67%
  5. Perkins CountyBest mid May · 16 checklists that week, 413 in all64%
  6. Gregory CountyBest early June · 15 checklists that week, 472 in all64%

Best spots

Share of checklists at the peak
  1. Newton Hills (Sargeant Creek)Lincoln County, best mid May · 25 checklists that week, 173 in all84%
  2. Farm IslandHughes County, best late May · 23 checklists that week, 825 in all73%
  3. Blood Run National Historic Landmark Area Tcf TractLincoln County, best early May · 29 checklists that week, 646 in all72%
  4. PerryMinnehaha County, best the second week of May · 29 checklists that week, 215 in all69%
  5. Alabaugh CanyonFall River County, best the second week of May · 38 checklists that week, 206 in all67%

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

Best time of day

In South Dakota, the Brown-headed Cowbird is most often listed on checklists started between 6 and 8 am (23% of those checklists).

0%10%20%30%40%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: 30% of 3387 checklists7 am: 20% of 7718 checklists8 am: 18% of 10342 checklists9 am: 15% of 10758 checklists10 am: 14% of 9123 checklists11 am: 12% of 7814 checklists12 pm: 11% of 6876 checklists1 pm: 9.8% of 6801 checklists2 pm: 9.3% of 6673 checklists3 pm: 9.7% of 6344 checklists4 pm: 9.1% of 6412 checklists5 pm: 11% of 5570 checklists6 pm: 12% of 4276 checklists7 pm: 16% 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
January0.4%0.1%0.1%0.1%
February0%0.2%0.3%0.2%
March0.5%0.6%1.5%1.5%
April3.5%8.7%12%20%
May33%35%38%35%
June32%30%27%27%
July27%23%15%10%
August6.7%5.1%3.2%2.5%
September1.6%1.6%1.3%1.1%
October1.0%1.3%0.9%0.6%
November0.6%0.4%0.2%0.1%
December0.1%0.1%0.2%0.4%

Neighboring states

  • Nebraska: arrives mid March, 2 weeks earlier than South Dakota
  • North Dakota: arrives mid April, 2 weeks later than South Dakota
  • Minnesota: arrives early April, in the same week than South Dakota
  • Iowa: arrives the second week of March, 3 weeks earlier than South Dakota

Common questions

When do Brown-headed Cowbirds arrive in South Dakota?
Brown-headed Cowbirds reach South Dakota in early April, are common by mid April, peak in mid May (36% of checklists), and most are gone by mid July.
When do Brown-headed Cowbirds leave South Dakota?
Most Brown-headed Cowbirds have left South Dakota by mid July, when reports fall below half their usual rate. Stragglers are still reported until mid August.
When is the best time to see a Brown-headed Cowbird in South Dakota?
The Brown-headed Cowbird is reported most often in mid May, on about 36% of South Dakota checklists.
Where in South Dakota are Brown-headed Cowbirds seen most often?
By county, Haakon County, Jones County, and Campbell County have the highest peak reporting rates for the Brown-headed Cowbird (counties with at least 200 checklists).