WhenToBird

Vireo bellii · Vireonidae

When Do Bell's Vireos Arrive in Arizona?

Adult male Bell's Vireo
Photo: Pat Farris, CC BY 4.0 via iNaturalist

Bell's Vireos reach Arizona in the second week of March, are common by late March, peak in mid April (17% of checklists), and most are gone by mid September.

When to look

First arrivalsMar 8-14the second week of March
Common byMar 22-31late March
PeakApr 15-21mid April
Most gone bySep 15-21mid September

Best: mid April. First arrivals the second week of March; most are gone by mid September. Peak: on about 17% of Arizona checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julpeak season
  8. Augpeak season
  9. Sepcommon
  10. Octuncommon
  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: 0.1% of 34758 checklistsJan 8-14: 0.1% of 29835 checklistsJan 15-21: 0.1% of 29279 checklistsJan 22-31: 0.1% of 39716 checklistsFeb 1-7: 0.1% of 27299 checklistsFeb 8-14: 0.1% of 28703 checklistsFeb 15-21: 0.1% of 35357 checklistsFeb 22-28: 0.1% of 29889 checklistsMar 1-7: 0.3% of 29932 checklistsMar 8-14: 1.2% of 32982 checklistsMar 15-21: 4.8% of 34731 checklistsMar 22-31: 11% of 50213 checklistsApr 1-7: 15% of 35788 checklistsApr 8-14: 17% of 38087 checklistsApr 15-21: 17% of 41520 checklistsApr 22-30: 17% of 55218 checklistsMay 1-7: 16% of 39688 checklistsMay 8-14: 16% of 39398 checklistsMay 15-21: 16% of 29562 checklistsMay 22-31: 16% of 36774 checklistsJun 1-7: 15% of 21313 checklistsJun 8-14: 15% of 19129 checklistsJun 15-21: 16% of 17922 checklistsJun 22-30: 17% of 21188 checklistsJul 1-7: 16% of 17325 checklistsJul 8-14: 15% of 16463 checklistsJul 15-21: 17% of 18642 checklistsJul 22-31: 16% of 31215 checklistsAug 1-7: 15% of 28163 checklistsAug 8-14: 14% of 31329 checklistsAug 15-21: 12% of 23878 checklistsAug 22-31: 12% of 28508 checklistsSep 1-7: 12% of 20878 checklistsSep 8-14: 12% of 19671 checklistsSep 15-21: 11% of 19859 checklistsSep 22-30: 6.6% of 25179 checklistsOct 1-7: 2.6% of 19420 checklistsOct 8-14: 0.6% of 21925 checklistsOct 15-21: 0.1% of 20995 checklistsOct 22-31: 0.1% of 29258 checklistsNov 1-7: 0.1% of 21269 checklistsNov 8-14: 0.1% of 22753 checklistsNov 15-21: 0.1% of 21982 checklistsNov 22-30: 0.1% of 29475 checklistsDec 1-7: 0.1% of 20810 checklistsDec 8-14: 0.1% of 22229 checklistsDec 15-21: 0.1% of 25148 checklistsDec 22-31: 0.1% of 39567 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 Arizona 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 Arizona

Best counties

Share of checklists at the peak
  1. Santa Cruz CountyBest early July · 1896 checklists that week, 162,726 in all32%
  2. Pima CountyBest late May · 10047 checklists that week, 437,722 in all29%
  3. Graham CountyBest late June · 164 checklists that week, 9,876 in all29%
  4. Pinal CountyBest the second week of May · 1251 checklists that week, 40,036 in all28%
  5. Gila CountyBest the second week of April · 414 checklists that week, 14,834 in all22%
  6. La Paz CountyBest late June · 67 checklists that week, 7,279 in all21%

Best spots

Share of checklists at the peak
  1. Coronado National Forest (Faber Spring)Pima County, best early July · 45 checklists that week, 5,353 in all95%
  2. Buenos Aires National Wildlife Refuge (Wilbur Wash)Pima County, best the second week of August · 21 checklists that week, 529 in all94%
  3. Coronado National Forest (Devils Cash Box)Santa Cruz County, best early July · 42 checklists that week, 2,933 in all93%
  4. Tonto National Forest (north 2)Maricopa County, best late April · 25 checklists that week, 671 in all93%
  5. Tanque Verde CreekPima County, best late June · 26 checklists that week, 2,051 in all92%
  6. Tumacacori National Historical ParkSanta Cruz County, best early July · 46 checklists that week, 5,914 in all92%

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

Best time of day

In Arizona, the Bell's Vireo 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 (488) to judge1 am: too few checklists (503) to judge2 am: too few checklists (489) to judge3 am: too few checklists (735) to judge4 am: too few checklists (4115) to judge5 am: 21% of 38350 checklists6 am: 18% of 118786 checklists7 am: 12% of 183415 checklists8 am: 8.5% of 187346 checklists9 am: 7.1% of 151342 checklists10 am: 6.1% of 124522 checklists11 am: 4.9% of 97088 checklists12 pm: 4.4% of 78110 checklists1 pm: 4.1% of 73059 checklists2 pm: 3.6% of 68912 checklists3 pm: 3.2% of 68060 checklists4 pm: 3.1% of 69387 checklists5 pm: 3.6% of 52951 checklists6 pm: 3.6% of 31061 checklists7 pm: too few checklists (16076) to judge8 pm: too few checklists (5352) to judge9 pm: too few checklists (2369) to judge10 pm: too few checklists (1100) to judge11 pm: too few checklists (604) 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%0.1%0.1%0.1%
February0.1%0.1%0.1%0.1%
March0.3%1.2%4.8%11%
April15%17%17%17%
May16%16%16%16%
June15%15%16%17%
July16%15%17%16%
August15%14%12%12%
September12%12%11%6.6%
October2.6%0.6%0.1%0.1%
November0.1%0.1%0.1%0.1%
December0.1%0.1%0.1%0.1%

Neighboring states

  • New Mexico: arrives the second week of April, 4 weeks later than Arizona
  • Nevada: arrives early April, 3 weeks later than Arizona
  • California: arrives early April, 3 weeks later than Arizona
  • Texas: arrives early April, 3 weeks later than Arizona

Common questions

When do Bell's Vireos arrive in Arizona?
Bell's Vireos reach Arizona in the second week of March, are common by late March, peak in mid April (17% of checklists), and most are gone by mid September.
When do Bell's Vireos leave Arizona?
Most Bell's Vireos have left Arizona by mid September, when reports fall below half their usual rate. Stragglers are still reported until early October.
When is the best time to see a Bell's Vireo in Arizona?
The Bell's Vireo is reported most often in mid April, on about 17% of Arizona checklists.
Where in Arizona are Bell's Vireos seen most often?
By county, Santa Cruz County, Pima County, and Graham County have the highest peak reporting rates for the Bell's Vireo (counties with at least 200 checklists).