WhenToBird

Vireo cassinii · Vireonidae

When Do Cassin's Vireos Arrive in New Mexico?

Adult Cassin's Vireo
Photo: David Anderson, CC BY 4.0 via iNaturalist

Cassin's Vireos mostly pass through New Mexico: they arrive in mid August, peak in the second week of September (3.3% of checklists), and most are gone by the second week of October.

When to look

First arrivalsAug 15-21mid August
Common byAug 15-21mid August
PeakSep 8-14the second week of September
Most gone byOct 8-14the second week of October

Best: the second week of September. First arrivals mid August; most are gone by the second week of October. Peak: on about 3.3% of New Mexico checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Apruncommon
  5. Mayuncommon
  6. Junrare
  7. Julnot usually seen
  8. Augcommon
  9. Seppeak season
  10. Octcommon
  11. Novnot usually seen
  12. Decnot usually seen

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

0%2%4%6%Jan 1-7: 0.1% of 11827 checklistsJan 8-14: 0% of 9370 checklistsJan 15-21: 0% of 9561 checklistsJan 22-31: 0% of 12707 checklistsFeb 1-7: 0% of 9365 checklistsFeb 8-14: 0% of 10141 checklistsFeb 15-21: 0% of 12431 checklistsFeb 22-28: 0% of 9159 checklistsMar 1-7: 0% of 9348 checklistsMar 8-14: 0% of 9704 checklistsMar 15-21: 0.1% of 9896 checklistsMar 22-31: 0.1% of 14679 checklistsApr 1-7: 0.2% of 11145 checklistsApr 8-14: 0.6% of 11939 checklistsApr 15-21: 0.9% of 12885 checklistsApr 22-30: 1.1% of 17935 checklistsMay 1-7: 1.1% of 15202 checklistsMay 8-14: 1.1% of 16604 checklistsMay 15-21: 0.8% of 12720 checklistsMay 22-31: 0.4% of 16699 checklistsJun 1-7: 0.1% of 9889 checklistsJun 8-14: 0% of 9322 checklistsJun 15-21: 0.1% of 8341 checklistsJun 22-30: 0% of 10562 checklistsJul 1-7: 0% of 9036 checklistsJul 8-14: 0% of 8461 checklistsJul 15-21: 0.1% of 8585 checklistsJul 22-31: 0% of 11800 checklistsAug 1-7: 0.1% of 8289 checklistsAug 8-14: 0.1% of 8882 checklistsAug 15-21: 0.6% of 9136 checklistsAug 22-31: 1.3% of 12662 checklistsSep 1-7: 2.9% of 9936 checklistsSep 8-14: 4.0% of 9581 checklistsSep 15-21: 2.9% of 9355 checklistsSep 22-30: 2.2% of 12402 checklistsOct 1-7: 1.0% of 9467 checklistsOct 8-14: 0.7% of 10279 checklistsOct 15-21: 0.2% of 8990 checklistsOct 22-31: 0.1% of 11986 checklistsNov 1-7: 0.1% of 8461 checklistsNov 8-14: 0.1% of 8801 checklistsNov 15-21: 0.1% of 8616 checklistsNov 22-30: 0.1% of 11088 checklistsDec 1-7: 0% of 8444 checklistsDec 8-14: 0.1% of 8575 checklistsDec 15-21: 0% of 10958 checklistsDec 22-31: 0% 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. Roosevelt CountyBest the second week of September · 148 checklists that week, 4,563 in all15%
  2. Lea CountyBest mid September · 69 checklists that week, 2,698 in all15%
  3. Torrance CountyBest the second week of September · 214 checklists that week, 4,945 in all7.5%
  4. De Baca CountyBest mid September · 98 checklists that week, 2,203 in all7.3%
  5. Guadalupe CountyBest mid September · 103 checklists that week, 2,614 in all7.0%
  6. Union CountyBest the second week of September · 39 checklists that week, 2,373 in all6.9%

Best spots

Share of checklists at the peak
  1. Estancia Park LakeTorrance County, best mid September · 21 checklists that week, 612 in all32%
  2. ResevoirLos Alamos County, best the second week of September · 21 checklists that week, 1,055 in all25%
  3. Ranch School TrailLos Alamos County, best the second week of September · 37 checklists that week, 1,691 in all24%
  4. Percha Dam State ParkSierra County, best the second week of September · 52 checklists that week, 1,881 in all21%

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

Best time of day

In New Mexico, the Cassin's Vireo is most often listed on checklists started between 6 and 8 am (0.9% of those checklists).

0%0.5%1%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: 1.0% of 29677 checklists7 am: 0.8% of 71785 checklists8 am: 0.7% of 79208 checklists9 am: 0.6% of 61605 checklists10 am: 0.4% of 49588 checklists11 am: 0.3% of 38079 checklists12 pm: 0.3% of 31089 checklists1 pm: 0.3% of 27524 checklists2 pm: 0.3% of 26644 checklists3 pm: 0.2% of 26849 checklists4 pm: 0.2% of 25156 checklists5 pm: 0.3% of 19061 checklists6 pm: 0.2% 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
January0.1%0%0%0%
February0%0%0%0%
March0%0%0.1%0.1%
April0.2%0.6%0.9%1.1%
May1.1%1.1%0.8%0.4%
June0.1%0%0.1%0%
July0%0%0.1%0%
August0.1%0.1%0.6%1.3%
September2.9%4.0%2.9%2.2%
October1.0%0.7%0.2%0.1%
November0.1%0.1%0.1%0.1%
December0%0.1%0%0%

Neighboring states

  • Arizona: arrives early March, 22 weeks earlier than New Mexico
  • Colorado: arrives late August, 1 week later than New Mexico
  • Utah: arrives late August, 1 week later than New Mexico
  • Nevada: arrives the second week of April, 17 weeks earlier than New Mexico

Common questions

When do Cassin's Vireos arrive in New Mexico?
Cassin's Vireos mostly pass through New Mexico: they arrive in mid August, peak in the second week of September (3.3% of checklists), and most are gone by the second week of October.
When do Cassin's Vireos leave New Mexico?
Most Cassin's Vireos have left New Mexico by the second week of October, when reports fall below half their usual rate.
When is the best time to see a Cassin's Vireo in New Mexico?
The Cassin's Vireo is reported most often in the second week of September, on about 3.3% of New Mexico checklists.
Where in New Mexico are Cassin's Vireos seen most often?
By county, Roosevelt County, Lea County, and Torrance County have the highest peak reporting rates for the Cassin's Vireo (counties with at least 200 checklists).