WhenToBird

Molothrus ater · Icteridae

When Do Brown-headed Cowbirds Arrive in Oklahoma?

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

Brown-headed Cowbirds reach Oklahoma in early January, are common by mid March, peak in the second week of May (34% of checklists), and most are gone by the second week of July.

When to look

First arrivalsJan 1-7early January
Common byMar 15-21mid March
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 January; most are gone by the second week of July. Peak: on about 34% of Oklahoma checklists.

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

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

0%10%20%30%40%Jan 1-7: 2.9% of 6087 checklistsJan 8-14: 3.6% of 4350 checklistsJan 15-21: 3.7% of 4381 checklistsJan 22-31: 3.5% of 6165 checklistsFeb 1-7: 4.2% of 4259 checklistsFeb 8-14: 5.6% of 4589 checklistsFeb 15-21: 5.8% of 7001 checklistsFeb 22-28: 7.8% of 4482 checklistsMar 1-7: 11% of 4724 checklistsMar 8-14: 14% of 4571 checklistsMar 15-21: 17% of 4393 checklistsMar 22-31: 24% of 7544 checklistsApr 1-7: 27% of 5967 checklistsApr 8-14: 30% of 6543 checklistsApr 15-21: 32% of 7366 checklistsApr 22-30: 31% of 10618 checklistsMay 1-7: 34% of 8835 checklistsMay 8-14: 34% of 8247 checklistsMay 15-21: 34% of 6081 checklistsMay 22-31: 32% of 7283 checklistsJun 1-7: 31% of 4256 checklistsJun 8-14: 31% of 3774 checklistsJun 15-21: 28% of 3541 checklistsJun 22-30: 28% of 4159 checklistsJul 1-7: 26% of 3209 checklistsJul 8-14: 20% of 2916 checklistsJul 15-21: 14% of 2861 checklistsJul 22-31: 6.2% of 4146 checklistsAug 1-7: 4.9% of 3043 checklistsAug 8-14: 3.3% of 2839 checklistsAug 15-21: 2.8% of 3014 checklistsAug 22-31: 2.6% of 4759 checklistsSep 1-7: 1.8% of 3861 checklistsSep 8-14: 1.6% of 3748 checklistsSep 15-21: 2.2% of 3569 checklistsSep 22-30: 4.3% of 4830 checklistsOct 1-7: 4.8% of 3809 checklistsOct 8-14: 4.4% of 4142 checklistsOct 15-21: 4.4% of 3705 checklistsOct 22-31: 3.7% of 4738 checklistsNov 1-7: 3.5% of 3823 checklistsNov 8-14: 2.8% of 3849 checklistsNov 15-21: 3.0% of 3722 checklistsNov 22-30: 2.0% of 4795 checklistsDec 1-7: 2.0% of 3324 checklistsDec 8-14: 1.7% of 3574 checklistsDec 15-21: 3.2% of 3884 checklistsDec 22-31: 2.6% of 5774 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 Oklahoma 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 Oklahoma

Best counties

Share of checklists at the peak
  1. Adair CountyBest mid April · 22 checklists that week, 616 in all69%
  2. Noble CountyBest early June · 10 checklists that week, 1,320 in all62%
  3. Washita CountyBest the second week of May · 20 checklists that week, 404 in all58%
  4. Johnston CountyBest the second week of May · 124 checklists that week, 4,464 in all58%
  5. Pawnee CountyBest mid June · 10 checklists that week, 948 in all55%
  6. Craig CountyBest late May · 21 checklists that week, 206 in all55%

Best spots

Share of checklists at the peak
  1. Washington Irving ParkTulsa County, best the second week of May · 32 checklists that week, 449 in all78%
  2. CLO Lands (Kenton)Cimarron County, best mid May · 21 checklists that week, 329 in all78%
  3. Joe B. Barnes Regional ParkOklahoma County, best late April · 23 checklists that week, 186 in all76%
  4. Upper Dog PondAlfalfa County, best late May · 26 checklists that week, 783 in all75%
  5. CLO LandsPayne County, best the second week of April · 24 checklists that week, 1,208 in all74%
  6. Sanborn Lake ParkPayne County, best mid May · 47 checklists that week, 992 in all70%

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

Best time of day

In Oklahoma, the Brown-headed Cowbird is most often listed on checklists started between 6 and 8 am (25% of those checklists).

0%10%20%30%40%12 am: too few checklists (91) to judge1 am: too few checklists (65) to judge2 am: too few checklists (73) to judge3 am: too few checklists (73) to judge4 am: too few checklists (100) to judge5 am: too few checklists (647) to judge6 am: 32% of 8353 checklists7 am: 22% of 24509 checklists8 am: 19% of 27848 checklists9 am: 17% of 25316 checklists10 am: 15% of 21161 checklists11 am: 12% of 18730 checklists12 pm: 10% of 16097 checklists1 pm: 11% of 14028 checklists2 pm: 9.4% of 13599 checklists3 pm: 9.3% of 14228 checklists4 pm: 9.3% of 14597 checklists5 pm: 11% of 12125 checklists6 pm: 14% of 9337 checklists7 pm: 14% of 6944 checklists8 pm: too few checklists (2403) to judge9 pm: too few checklists (459) to judge10 pm: too few checklists (226) to judge11 pm: too few checklists (141) 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
January2.9%3.6%3.7%3.5%
February4.2%5.6%5.8%7.8%
March11%14%17%24%
April27%30%32%31%
May34%34%34%32%
June31%31%28%28%
July26%20%14%6.2%
August4.9%3.3%2.8%2.6%
September1.8%1.6%2.2%4.3%
October4.8%4.4%4.4%3.7%
November3.5%2.8%3.0%2.0%
December2.0%1.7%3.2%2.6%

Neighboring states

  • Kansas: arrives early March, 8 weeks later than Oklahoma
  • Arkansas: arrives mid March, 10 weeks later than Oklahoma
  • Missouri: arrives mid February, 6 weeks later than Oklahoma
  • Nebraska: arrives mid March, 10 weeks later than Oklahoma

Common questions

When do Brown-headed Cowbirds arrive in Oklahoma?
Brown-headed Cowbirds reach Oklahoma in early January, are common by mid March, peak in the second week of May (34% of checklists), and most are gone by the second week of July.
When do Brown-headed Cowbirds leave Oklahoma?
Most Brown-headed Cowbirds have left Oklahoma 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 Oklahoma?
The Brown-headed Cowbird is reported most often in the second week of May, on about 34% of Oklahoma checklists.
Where in Oklahoma are Brown-headed Cowbirds seen most often?
By county, Adair County, Noble County, and Washita County have the highest peak reporting rates for the Brown-headed Cowbird (counties with at least 200 checklists).