WhenToBird

Molothrus ater · Icteridae

When Do Brown-headed Cowbirds Arrive in Kentucky?

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

Brown-headed Cowbirds are in Kentucky all year, but most are here in spring: numbers build from late March, peak in late April (45% of checklists), and fall back by early July. In the quietest week (the second week of December) they are still on about 2.6% of checklists.

When to look

Numbers buildMar 22-31late March
PeakApr 22-30late April
Fall back byJul 1-7early July
FewestDec 8-14the second week of December

Best: late April. Here all year; numbers build from late March and fall back by early July. Peak: on about 45% of Kentucky checklists.

  1. Janrare
  2. Febuncommon
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Seprare
  10. Octrare
  11. Novrare
  12. Decrare

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

0%20%40%60%Jan 1-7: 3.7% of 6923 checklistsJan 8-14: 4.9% of 4900 checklistsJan 15-21: 6.4% of 5016 checklistsJan 22-31: 4.4% of 6611 checklistsFeb 1-7: 4.2% of 4986 checklistsFeb 8-14: 6.0% of 5677 checklistsFeb 15-21: 6.2% of 8880 checklistsFeb 22-28: 5.8% of 5567 checklistsMar 1-7: 9.4% of 5397 checklistsMar 8-14: 13% of 5462 checklistsMar 15-21: 18% of 5733 checklistsMar 22-31: 27% of 9043 checklistsApr 1-7: 38% of 6763 checklistsApr 8-14: 42% of 7498 checklistsApr 15-21: 45% of 8486 checklistsApr 22-30: 45% of 13396 checklistsMay 1-7: 44% of 10825 checklistsMay 8-14: 42% of 11495 checklistsMay 15-21: 42% of 7363 checklistsMay 22-31: 38% of 8800 checklistsJun 1-7: 36% of 5381 checklistsJun 8-14: 34% of 5244 checklistsJun 15-21: 34% of 4730 checklistsJun 22-30: 32% of 5470 checklistsJul 1-7: 27% of 4567 checklistsJul 8-14: 22% of 4287 checklistsJul 15-21: 14% of 4097 checklistsJul 22-31: 8.5% of 6044 checklistsAug 1-7: 6.4% of 4647 checklistsAug 8-14: 6.2% of 4256 checklistsAug 15-21: 5.3% of 4484 checklistsAug 22-31: 4.7% of 6434 checklistsSep 1-7: 3.4% of 5450 checklistsSep 8-14: 3.0% of 5157 checklistsSep 15-21: 2.8% of 5530 checklistsSep 22-30: 3.5% of 6710 checklistsOct 1-7: 5.3% of 5403 checklistsOct 8-14: 5.9% of 5943 checklistsOct 15-21: 5.5% of 4873 checklistsOct 22-31: 5.0% of 6584 checklistsNov 1-7: 3.9% of 5008 checklistsNov 8-14: 3.2% of 4677 checklistsNov 15-21: 3.5% of 4419 checklistsNov 22-30: 3.3% of 5933 checklistsDec 1-7: 2.9% of 4479 checklistsDec 8-14: 2.2% of 4687 checklistsDec 15-21: 2.6% of 6239 checklistsDec 22-31: 3.4% of 7976 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 Kentucky 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 Kentucky

Best counties

Share of checklists at the peak
  1. Morgan CountyBest early July · 10 checklists that week, 282 in all86%
  2. Butler CountyBest the second week of April · 15 checklists that week, 267 in all77%
  3. Spencer CountyBest early May · 147 checklists that week, 7,721 in all73%
  4. Hart CountyBest mid June · 47 checklists that week, 2,263 in all65%
  5. Ohio CountyBest late April · 14 checklists that week, 440 in all62%
  6. Oldham CountyBest mid April · 133 checklists that week, 6,659 in all60%

Best spots

Share of checklists at the peak
  1. Harrods Creek ParkJefferson County, best the second week of May · 37 checklists that week, 699 in all88%
  2. Central Park and ArboretumBoone County, best the second week of May · 48 checklists that week, 1,695 in all87%
  3. Parklands of Floyds ForkJefferson County, best late May · 31 checklists that week, 741 in all83%
  4. Land Between the Lakes National Recreation Area (O'Brien Branch)Lyon County, best early May · 23 checklists that week, 177 in all82%

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

Best time of day

In Kentucky, the Brown-headed Cowbird is most often listed on checklists started between 6 and 8 am (30% of those checklists).

0%10%20%30%40%12 am: too few checklists (140) to judge1 am: too few checklists (120) to judge2 am: too few checklists (88) to judge3 am: too few checklists (95) to judge4 am: too few checklists (151) to judge5 am: too few checklists (1289) to judge6 am: 34% of 8227 checklists7 am: 28% of 24608 checklists8 am: 25% of 36577 checklists9 am: 21% of 34626 checklists10 am: 18% of 28796 checklists11 am: 15% of 22781 checklists12 pm: 14% of 19848 checklists1 pm: 12% of 19369 checklists2 pm: 12% of 19367 checklists3 pm: 11% of 19618 checklists4 pm: 12% of 19464 checklists5 pm: 15% of 16639 checklists6 pm: 16% of 12714 checklists7 pm: 16% of 8457 checklists8 pm: too few checklists (3447) to judge9 pm: too few checklists (684) to judge10 pm: too few checklists (267) to judge11 pm: too few checklists (158) 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
January3.7%4.9%6.4%4.4%
February4.2%6.0%6.2%5.8%
March9.4%13%18%27%
April38%42%45%45%
May44%42%42%38%
June36%34%34%32%
July27%22%14%8.5%
August6.4%6.2%5.3%4.7%
September3.4%3.0%2.8%3.5%
October5.3%5.9%5.5%5.0%
November3.9%3.2%3.5%3.3%
December2.9%2.2%2.6%3.4%

Neighboring states

  • Tennessee: arrives mid March, 1 week earlier than Kentucky
  • Indiana: arrives mid February, 5 weeks earlier than Kentucky
  • Ohio: arrives the second week of February, 6 weeks earlier than Kentucky
  • Illinois: arrives mid February, 5 weeks earlier than Kentucky

Common questions

When do Brown-headed Cowbirds arrive in Kentucky?
Brown-headed Cowbirds are in Kentucky all year, but most are here in spring: numbers build from late March, peak in late April (45% of checklists), and fall back by early July. In the quietest week (the second week of December) they are still on about 2.6% of checklists.
When do Brown-headed Cowbirds leave Kentucky?
Brown-headed Cowbirds never fully leave Kentucky: numbers fall back below half their usual rate by early July, but some are still reported in every week, about 2.6% of checklists at the low.
When is the best time to see a Brown-headed Cowbird in Kentucky?
The Brown-headed Cowbird is reported most often in late April, on about 45% of Kentucky checklists.
Where in Kentucky are Brown-headed Cowbirds seen most often?
By county, Morgan County, Butler County, and Spencer County have the highest peak reporting rates for the Brown-headed Cowbird (counties with at least 200 checklists).