WhenToBird

Molothrus ater · Icteridae

When Do Brown-headed Cowbirds Arrive in Nevada?

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

Brown-headed Cowbirds reach Nevada in late March, are common by mid April, peak in the second week of May (21% of checklists), and most are gone by early August.

When to look

First arrivalsMar 22-31late March
Common byApr 15-21mid April
PeakMay 8-14the second week of May
Most gone byAug 1-7early August

Best: the second week of May. First arrivals late March; most are gone by early August. Peak: on about 21% of Nevada checklists.

  1. Janrare
  2. Febrare
  3. Marrare
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julpeak season
  8. Augcommon
  9. Sepuncommon
  10. Octrare
  11. Novrare
  12. Decrare

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

0%10%20%30%Jan 1-7: 1.4% of 5121 checklistsJan 8-14: 1.3% of 3908 checklistsJan 15-21: 1.1% of 4000 checklistsJan 22-31: 1.1% of 4991 checklistsFeb 1-7: 1.5% of 3377 checklistsFeb 8-14: 1.3% of 3747 checklistsFeb 15-21: 0.8% of 4852 checklistsFeb 22-28: 0.9% of 3712 checklistsMar 1-7: 1.4% of 3745 checklistsMar 8-14: 0.9% of 3763 checklistsMar 15-21: 1.4% of 4188 checklistsMar 22-31: 2.1% of 6027 checklistsApr 1-7: 2.6% of 4679 checklistsApr 8-14: 6.0% of 4609 checklistsApr 15-21: 12% of 4709 checklistsApr 22-30: 18% of 6984 checklistsMay 1-7: 21% of 5702 checklistsMay 8-14: 22% of 5928 checklistsMay 15-21: 22% of 5353 checklistsMay 22-31: 21% of 7352 checklistsJun 1-7: 21% of 4360 checklistsJun 8-14: 17% of 4183 checklistsJun 15-21: 18% of 3751 checklistsJun 22-30: 18% of 4126 checklistsJul 1-7: 17% of 3231 checklistsJul 8-14: 17% of 3024 checklistsJul 15-21: 15% of 2967 checklistsJul 22-31: 12% of 4212 checklistsAug 1-7: 8.6% of 2828 checklistsAug 8-14: 8.2% of 3036 checklistsAug 15-21: 7.1% of 3076 checklistsAug 22-31: 8.2% of 4345 checklistsSep 1-7: 6.4% of 3369 checklistsSep 8-14: 5.3% of 3728 checklistsSep 15-21: 4.6% of 3535 checklistsSep 22-30: 2.0% of 5028 checklistsOct 1-7: 2.6% of 3976 checklistsOct 8-14: 2.6% of 3781 checklistsOct 15-21: 1.8% of 3577 checklistsOct 22-31: 1.8% of 4986 checklistsNov 1-7: 1.6% of 3592 checklistsNov 8-14: 1.5% of 3685 checklistsNov 15-21: 1.5% of 3399 checklistsNov 22-30: 0.9% of 4544 checklistsDec 1-7: 1.2% of 3162 checklistsDec 8-14: 1.1% of 3191 checklistsDec 15-21: 1.3% of 3615 checklistsDec 22-31: 1.1% of 5101 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 Nevada 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 Nevada

Best counties

Share of checklists at the peak
  1. Esmeralda CountyBest mid July · 11 checklists that week, 2,275 in all47%
  2. Carson CityBest late May · 217 checklists that week, 6,992 in all40%
  3. Douglas CountyBest late May · 264 checklists that week, 7,476 in all34%
  4. Lyon CountyBest early June · 102 checklists that week, 3,229 in all32%
  5. Storey CountyBest the second week of May · 65 checklists that week, 1,593 in all31%
  6. Washoe CountyBest mid May · 1356 checklists that week, 53,497 in all31%

Best spots

Share of checklists at the peak
  1. River Fork Ranch PreserveDouglas County, best late May · 22 checklists that week, 371 in all81%
  2. Lockwood Open SpaceWashoe County, best late April · 22 checklists that week, 472 in all81%
  3. Mccarran Ranch PreserveStorey County, best early May · 21 checklists that week, 293 in all78%
  4. Toiyabe National ForestWashoe County, best early May · 23 checklists that week, 877 in all75%
  5. Toiyabe National Forest (Burke Creek)Douglas County, best mid June · 23 checklists that week, 441 in all73%

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

Best time of day

In Nevada, the Brown-headed Cowbird is most often listed on checklists started between 5 and 7 am (19% of those checklists).

0%10%20%30%12 am: too few checklists (114) to judge1 am: too few checklists (99) to judge2 am: too few checklists (71) to judge3 am: too few checklists (108) to judge4 am: too few checklists (459) to judge5 am: 27% of 4313 checklists6 am: 17% of 17070 checklists7 am: 11% of 27389 checklists8 am: 8.4% of 24858 checklists9 am: 6.8% of 22012 checklists10 am: 5.2% of 19284 checklists11 am: 4.7% of 15592 checklists12 pm: 4.2% of 12432 checklists1 pm: 3.8% of 11386 checklists2 pm: 3.5% of 11262 checklists3 pm: 4.0% of 10721 checklists4 pm: 4.4% of 9090 checklists5 pm: 6.2% of 6397 checklists6 pm: 6.2% of 5012 checklists7 pm: too few checklists (3026) to judge8 pm: too few checklists (905) to judge9 pm: too few checklists (271) to judge10 pm: too few checklists (164) to judge11 pm: too few checklists (120) 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
January1.4%1.3%1.1%1.1%
February1.5%1.3%0.8%0.9%
March1.4%0.9%1.4%2.1%
April2.6%6.0%12%18%
May21%22%22%21%
June21%17%18%18%
July17%17%15%12%
August8.6%8.2%7.1%8.2%
September6.4%5.3%4.6%2.0%
October2.6%2.6%1.8%1.8%
November1.6%1.5%1.5%0.9%
December1.2%1.1%1.3%1.1%

Neighboring states

  • California: arrives mid February, 5 weeks earlier than Nevada
  • Utah: arrives mid April, 3 weeks later than Nevada
  • Idaho: arrives mid April, 3 weeks later than Nevada
  • Arizona: arrives the second week of March, 2 weeks earlier than Nevada

Common questions

When do Brown-headed Cowbirds arrive in Nevada?
Brown-headed Cowbirds reach Nevada in late March, are common by mid April, peak in the second week of May (21% of checklists), and most are gone by early August.
When do Brown-headed Cowbirds leave Nevada?
Most Brown-headed Cowbirds have left Nevada by early August, when reports fall below half their usual rate. Stragglers are still reported until early November.
When is the best time to see a Brown-headed Cowbird in Nevada?
The Brown-headed Cowbird is reported most often in the second week of May, on about 21% of Nevada checklists.
Where in Nevada are Brown-headed Cowbirds seen most often?
By county, Esmeralda County, Carson City, and Douglas County have the highest peak reporting rates for the Brown-headed Cowbird (counties with at least 200 checklists).