WhenToBird

Molothrus ater · Icteridae

When Do Brown-headed Cowbirds Arrive in Minnesota?

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

Brown-headed Cowbirds reach Minnesota in early April, are common by mid April, peak in the second week of May (37% of checklists), and most are gone by the second week of July.

When to look

First arrivalsApr 1-7early April
Common byApr 15-21mid April
PeakMay 8-14the second week of May
Most gone byJul 8-14the second week of July

Best: the second week of May. First arrivals early April; most are gone by the second week of July. Peak: on about 37% of Minnesota checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marrare
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Augrare
  9. Sepnot usually seen
  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: 0.2% of 20628 checklistsJan 8-14: 0.1% of 14594 checklistsJan 15-21: 0.1% of 14238 checklistsJan 22-31: 0.1% of 20725 checklistsFeb 1-7: 0.1% of 14484 checklistsFeb 8-14: 0.1% of 15988 checklistsFeb 15-21: 0.1% of 20718 checklistsFeb 22-28: 0.2% of 15754 checklistsMar 1-7: 0.2% of 16125 checklistsMar 8-14: 0.4% of 19035 checklistsMar 15-21: 0.7% of 19586 checklistsMar 22-31: 1.4% of 30192 checklistsApr 1-7: 4.4% of 24262 checklistsApr 8-14: 12% of 30223 checklistsApr 15-21: 17% of 29085 checklistsApr 22-30: 27% of 43574 checklistsMay 1-7: 37% of 39300 checklistsMay 8-14: 38% of 45927 checklistsMay 15-21: 35% of 36632 checklistsMay 22-31: 32% of 43809 checklistsJun 1-7: 31% of 23418 checklistsJun 8-14: 31% of 20450 checklistsJun 15-21: 29% of 19470 checklistsJun 22-30: 28% of 23418 checklistsJul 1-7: 24% of 19104 checklistsJul 8-14: 19% of 16927 checklistsJul 15-21: 12% of 15635 checklistsJul 22-31: 5.9% of 22073 checklistsAug 1-7: 4.0% of 16255 checklistsAug 8-14: 3.3% of 16840 checklistsAug 15-21: 2.2% of 17475 checklistsAug 22-31: 1.2% of 26545 checklistsSep 1-7: 0.7% of 20750 checklistsSep 8-14: 0.4% of 18494 checklistsSep 15-21: 0.4% of 18215 checklistsSep 22-30: 0.6% of 24463 checklistsOct 1-7: 0.6% of 18252 checklistsOct 8-14: 0.6% of 19527 checklistsOct 15-21: 0.7% of 17098 checklistsOct 22-31: 0.4% of 24570 checklistsNov 1-7: 0.2% of 16744 checklistsNov 8-14: 0.2% of 13483 checklistsNov 15-21: 0.1% of 12525 checklistsNov 22-30: 0.1% of 17023 checklistsDec 1-7: 0.2% of 11645 checklistsDec 8-14: 0.1% of 11567 checklistsDec 15-21: 0.2% of 13343 checklistsDec 22-31: 0.1% of 19759 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 Minnesota 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 Minnesota

Best counties

Share of checklists at the peak
  1. Lyon CountyBest mid June · 69 checklists that week, 4,283 in all66%
  2. Steele CountyBest early June · 135 checklists that week, 4,784 in all60%
  3. Yellow Medicine CountyBest the second week of June · 31 checklists that week, 1,931 in all60%
  4. Benton CountyBest late May · 191 checklists that week, 6,111 in all56%
  5. Lac qui Parle CountyBest mid June · 53 checklists that week, 3,681 in all55%
  6. Renville CountyBest mid May · 75 checklists that week, 2,020 in all53%

Best spots

Share of checklists at the peak
  1. Gables LakeWashington County, best early May · 47 checklists that week, 1,181 in all90%
  2. Centerville LakeAnoka County, best the second week of May · 24 checklists that week, 628 in all88%
  3. Western Waterfront TrailSt. Louis County, best late June · 51 checklists that week, 1,973 in all85%
  4. Frontenac State Park (west)Goodhue County, best late May · 22 checklists that week, 463 in all84%
  5. Louisville SwampScott County, best the second week of May · 49 checklists that week, 562 in all84%

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

Best time of day

In Minnesota, the Brown-headed Cowbird is most often listed on checklists started between 6 and 8 am (21% of those checklists).

0%10%20%30%12 am: too few checklists (349) to judge1 am: too few checklists (331) to judge2 am: too few checklists (286) to judge3 am: too few checklists (364) to judge4 am: too few checklists (863) to judge5 am: too few checklists (7598) to judge6 am: 29% of 35775 checklists7 am: 18% of 90565 checklists8 am: 15% of 110612 checklists9 am: 13% of 106128 checklists10 am: 11% of 96131 checklists11 am: 9.4% of 83750 checklists12 pm: 8.3% of 76254 checklists1 pm: 7.6% of 73480 checklists2 pm: 7.2% of 73703 checklists3 pm: 7.2% of 75249 checklists4 pm: 8.1% of 68810 checklists5 pm: 10% of 51899 checklists6 pm: 12% of 38524 checklists7 pm: 13% of 25120 checklists8 pm: too few checklists (10568) to judge9 pm: too few checklists (2420) to judge10 pm: too few checklists (748) to judge11 pm: too few checklists (420) 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
January0.2%0.1%0.1%0.1%
February0.1%0.1%0.1%0.2%
March0.2%0.4%0.7%1.4%
April4.4%12%17%27%
May37%38%35%32%
June31%31%29%28%
July24%19%12%5.9%
August4.0%3.3%2.2%1.2%
September0.7%0.4%0.4%0.6%
October0.6%0.6%0.7%0.4%
November0.2%0.2%0.1%0.1%
December0.2%0.1%0.2%0.1%

Neighboring states

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

Common questions

When do Brown-headed Cowbirds arrive in Minnesota?
Brown-headed Cowbirds reach Minnesota in early April, are common by mid April, peak in the second week of May (37% of checklists), and most are gone by the second week of July.
When do Brown-headed Cowbirds leave Minnesota?
Most Brown-headed Cowbirds have left Minnesota by the second week of July, when reports fall below half their usual rate. Stragglers are still reported until the second week of August.
When is the best time to see a Brown-headed Cowbird in Minnesota?
The Brown-headed Cowbird is reported most often in the second week of May, on about 37% of Minnesota checklists.
Where in Minnesota are Brown-headed Cowbirds seen most often?
By county, Lyon County, Steele County, and Yellow Medicine County have the highest peak reporting rates for the Brown-headed Cowbird (counties with at least 200 checklists).