WhenToBird

Molothrus ater · Icteridae

When Do Brown-headed Cowbirds Arrive in New Mexico?

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

Brown-headed Cowbirds reach New Mexico in the second week of April, are common by late April, peak in mid May (17% of checklists), and most are gone by late July.

When to look

First arrivalsApr 8-14the second week of April
Common byApr 22-30late April
PeakMay 15-21mid May
Most gone byJul 22-31late July

Best: mid May. First arrivals the second week of April; most are gone by late July. Peak: on about 17% of New Mexico checklists.

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

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

0%5%10%15%20%Jan 1-7: 0.5% of 11827 checklistsJan 8-14: 0.3% of 9370 checklistsJan 15-21: 0.4% of 9561 checklistsJan 22-31: 0.3% of 12707 checklistsFeb 1-7: 0.3% of 9365 checklistsFeb 8-14: 0.4% of 10141 checklistsFeb 15-21: 0.3% of 12431 checklistsFeb 22-28: 0.4% of 9159 checklistsMar 1-7: 0.3% of 9348 checklistsMar 8-14: 0.6% of 9704 checklistsMar 15-21: 0.6% of 9896 checklistsMar 22-31: 0.8% of 14679 checklistsApr 1-7: 1.0% of 11145 checklistsApr 8-14: 1.6% of 11939 checklistsApr 15-21: 3.4% of 12885 checklistsApr 22-30: 8.6% of 17935 checklistsMay 1-7: 14% of 15202 checklistsMay 8-14: 17% of 16604 checklistsMay 15-21: 18% of 12720 checklistsMay 22-31: 17% of 16699 checklistsJun 1-7: 16% of 9889 checklistsJun 8-14: 15% of 9322 checklistsJun 15-21: 14% of 8341 checklistsJun 22-30: 14% of 10562 checklistsJul 1-7: 13% of 9036 checklistsJul 8-14: 14% of 8461 checklistsJul 15-21: 13% of 8585 checklistsJul 22-31: 9.0% of 11800 checklistsAug 1-7: 4.3% of 8289 checklistsAug 8-14: 3.6% of 8882 checklistsAug 15-21: 3.0% of 9136 checklistsAug 22-31: 2.3% of 12662 checklistsSep 1-7: 2.2% of 9936 checklistsSep 8-14: 1.6% of 9581 checklistsSep 15-21: 1.1% of 9355 checklistsSep 22-30: 0.9% of 12402 checklistsOct 1-7: 0.7% of 9467 checklistsOct 8-14: 0.6% of 10279 checklistsOct 15-21: 0.4% of 8990 checklistsOct 22-31: 0.5% of 11986 checklistsNov 1-7: 0.3% of 8461 checklistsNov 8-14: 0.2% of 8801 checklistsNov 15-21: 0.1% of 8616 checklistsNov 22-30: 0.3% of 11088 checklistsDec 1-7: 0.5% of 8444 checklistsDec 8-14: 0.3% of 8575 checklistsDec 15-21: 0.3% of 10958 checklistsDec 22-31: 0.2% of 14523 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 New Mexico 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 New Mexico

Best counties

Share of checklists at the peak
  1. Sierra CountyBest early June · 137 checklists that week, 13,458 in all40%
  2. De Baca CountyBest late July · 15 checklists that week, 2,203 in all38%
  3. Valencia CountyBest the second week of June · 144 checklists that week, 8,351 in all32%
  4. Socorro CountyBest mid June · 322 checklists that week, 33,508 in all31%
  5. Eddy CountyBest the second week of June · 192 checklists that week, 11,011 in all27%
  6. Luna CountyBest early July · 21 checklists that week, 3,814 in all27%

Best spots

Share of checklists at the peak
  1. GalisteoSanta Fe County, best early June · 21 checklists that week, 1,070 in all72%
  2. StablesLos Alamos County, best early May · 28 checklists that week, 883 in all68%
  3. City of Albuquerque 1Bernalillo County, best the second week of June · 28 checklists that week, 1,806 in all66%
  4. Bosque (Los Padillas)Bernalillo County, best the second week of June · 25 checklists that week, 1,047 in all64%
  5. Ute Lake State ParkQuay County, best late May · 22 checklists that week, 415 in all62%

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

Best time of day

In New Mexico, the Brown-headed Cowbird is most often listed on checklists started between 6 and 8 am (9.5% of those checklists).

0%5%10%15%12 am: too few checklists (186) to judge1 am: too few checklists (180) to judge2 am: too few checklists (172) to judge3 am: too few checklists (183) to judge4 am: too few checklists (527) to judge5 am: too few checklists (4013) to judge6 am: 14% of 29677 checklists7 am: 7.7% of 71785 checklists8 am: 6.4% of 79208 checklists9 am: 4.3% of 61605 checklists10 am: 3.2% of 49588 checklists11 am: 2.7% of 38079 checklists12 pm: 2.1% of 31089 checklists1 pm: 1.9% of 27524 checklists2 pm: 1.9% of 26644 checklists3 pm: 1.8% of 26849 checklists4 pm: 2.3% of 25156 checklists5 pm: 2.7% of 19061 checklists6 pm: 4.0% of 15112 checklists7 pm: too few checklists (9040) to judge8 pm: too few checklists (2738) to judge9 pm: too few checklists (736) to judge10 pm: too few checklists (384) to judge11 pm: too few checklists (208) 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
January0.5%0.3%0.4%0.3%
February0.3%0.4%0.3%0.4%
March0.3%0.6%0.6%0.8%
April1.0%1.6%3.4%8.6%
May14%17%18%17%
June16%15%14%14%
July13%14%13%9.0%
August4.3%3.6%3.0%2.3%
September2.2%1.6%1.1%0.9%
October0.7%0.6%0.4%0.5%
November0.3%0.2%0.1%0.3%
December0.5%0.3%0.3%0.2%

Neighboring states

  • Arizona: arrives the second week of March, 4 weeks earlier than New Mexico
  • Colorado: arrives the second week of April, in the same week than New Mexico
  • Utah: arrives mid April, 1 week later than New Mexico
  • Oklahoma: arrives early January, 13 weeks earlier than New Mexico

Common questions

When do Brown-headed Cowbirds arrive in New Mexico?
Brown-headed Cowbirds reach New Mexico in the second week of April, are common by late April, peak in mid May (17% of checklists), and most are gone by late July.
When do Brown-headed Cowbirds leave New Mexico?
Most Brown-headed Cowbirds have left New Mexico by late July, when reports fall below half their usual rate. Stragglers are still reported until the second week of September.
When is the best time to see a Brown-headed Cowbird in New Mexico?
The Brown-headed Cowbird is reported most often in mid May, on about 17% of New Mexico checklists.
Where in New Mexico are Brown-headed Cowbirds seen most often?
By county, Sierra County, De Baca County, and Valencia County have the highest peak reporting rates for the Brown-headed Cowbird (counties with at least 200 checklists).