WhenToBird

Pooecetes gramineus · Passerellidae

When Do Vesper Sparrows Arrive in Colorado?

Adult Vesper Sparrow
Photo: Dani Alba, CC BY 4.0 via iNaturalist

Vesper Sparrows reach Colorado in early April, are common by the second week of April, peak in the second week of September (10% of checklists), and most are gone by early October.

When to look

First arrivalsApr 1-7early April
Common byApr 8-14the second week of April
PeakSep 8-14the second week of September
Most gone byOct 1-7early October

Best: the second week of September. First arrivals early April; most are gone by early October. Peak: on about 10% of Colorado checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprcommon
  5. Maycommon
  6. Juncommon
  7. Julcommon
  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%5%10%15%Jan 1-7: 0% of 32254 checklistsJan 8-14: 0.1% of 23278 checklistsJan 15-21: 0% of 22933 checklistsJan 22-31: 0.1% of 30856 checklistsFeb 1-7: 0.1% of 21464 checklistsFeb 8-14: 0% of 22910 checklistsFeb 15-21: 0.1% of 28739 checklistsFeb 22-28: 0% of 21833 checklistsMar 1-7: 0.1% of 23066 checklistsMar 8-14: 0.1% of 23783 checklistsMar 15-21: 0.1% of 24797 checklistsMar 22-31: 0.1% of 38439 checklistsApr 1-7: 0.6% of 31676 checklistsApr 8-14: 2.4% of 35092 checklistsApr 15-21: 5.8% of 36778 checklistsApr 22-30: 7.3% of 50885 checklistsMay 1-7: 8.1% of 44186 checklistsMay 8-14: 6.5% of 49011 checklistsMay 15-21: 5.9% of 40784 checklistsMay 22-31: 5.6% of 53073 checklistsJun 1-7: 6.0% of 32432 checklistsJun 8-14: 6.1% of 29978 checklistsJun 15-21: 6.0% of 29457 checklistsJun 22-30: 6.3% of 36072 checklistsJul 1-7: 6.3% of 28857 checklistsJul 8-14: 5.4% of 27224 checklistsJul 15-21: 4.7% of 27629 checklistsJul 22-31: 3.9% of 37318 checklistsAug 1-7: 3.8% of 25893 checklistsAug 8-14: 4.2% of 24870 checklistsAug 15-21: 4.6% of 24035 checklistsAug 22-31: 6.2% of 35691 checklistsSep 1-7: 9.2% of 27068 checklistsSep 8-14: 11% of 26709 checklistsSep 15-21: 9.7% of 26098 checklistsSep 22-30: 7.4% of 31550 checklistsOct 1-7: 4.1% of 24110 checklistsOct 8-14: 1.8% of 23352 checklistsOct 15-21: 0.5% of 21895 checklistsOct 22-31: 0.1% of 28319 checklistsNov 1-7: 0.1% of 21698 checklistsNov 8-14: 0.1% of 21061 checklistsNov 15-21: 0.1% of 19855 checklistsNov 22-30: 0.1% of 25798 checklistsDec 1-7: 0.1% of 18626 checklistsDec 8-14: 0% of 19004 checklistsDec 15-21: 0.1% of 23103 checklistsDec 22-31: 0.1% of 30802 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 Colorado 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 Colorado

Best counties

Share of checklists at the peak
  1. Cheyenne CountyBest early October · 21 checklists that week, 1,388 in all46%
  2. Lincoln CountyBest late September · 69 checklists that week, 2,707 in all40%
  3. Sedgwick CountyBest early October · 27 checklists that week, 1,168 in all38%
  4. Baca CountyBest early October · 50 checklists that week, 3,209 in all38%
  5. Kiowa CountyBest late September · 85 checklists that week, 3,854 in all37%
  6. Kit Carson CountyBest late September · 74 checklists that week, 2,633 in all31%

Best spots

Share of checklists at the peak
  1. Dan Noble State Wildlife AreaSan Miguel County, best the second week of September · 20 checklists that week, 399 in all92%
  2. Rueter-Hess ReservoirDouglas County, best the second week of May · 23 checklists that week, 742 in all87%
  3. Walker Ranch ParkBoulder County, best late June · 31 checklists that week, 365 in all84%
  4. Wrights ReservoirTeller County, best mid May · 23 checklists that week, 431 in all84%
  5. Coal Creek Canyon Study AreaJefferson County, best late June · 81 checklists that week, 998 in all82%
  6. Soapstone Prairie Natural AreaLarimer County, best late July · 20 checklists that week, 295 in all79%

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

Best time of day

In Colorado, the Vesper Sparrow is most often listed on checklists started between 6 and 8 am (5.2% of those checklists).

0%2%4%6%8%12 am: too few checklists (512) to judge1 am: too few checklists (468) to judge2 am: too few checklists (513) to judge3 am: too few checklists (656) to judge4 am: too few checklists (1918) to judge5 am: too few checklists (16045) to judge6 am: 6.3% of 71991 checklists7 am: 4.7% of 159189 checklists8 am: 4.2% of 177206 checklists9 am: 3.9% of 165269 checklists10 am: 3.3% of 141029 checklists11 am: 3.0% of 115283 checklists12 pm: 2.6% of 96068 checklists1 pm: 2.4% of 89512 checklists2 pm: 2.3% of 86319 checklists3 pm: 2.2% of 82496 checklists4 pm: 2.5% of 71648 checklists5 pm: 3.0% of 52445 checklists6 pm: 3.2% of 40199 checklists7 pm: too few checklists (24246) to judge8 pm: too few checklists (7986) to judge9 pm: too few checklists (2004) to judge10 pm: too few checklists (888) to judge11 pm: too few checklists (450) 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%0.1%0%0.1%
February0.1%0%0.1%0%
March0.1%0.1%0.1%0.1%
April0.6%2.4%5.8%7.3%
May8.1%6.5%5.9%5.6%
June6.0%6.1%6.0%6.3%
July6.3%5.4%4.7%3.9%
August3.8%4.2%4.6%6.2%
September9.2%11%9.7%7.4%
October4.1%1.8%0.5%0.1%
November0.1%0.1%0.1%0.1%
December0.1%0%0.1%0.1%

Neighboring states

  • Wyoming: arrives the second week of April, 1 week later than Colorado
  • New Mexico: arrives early March, 4 weeks earlier than Colorado
  • Utah: arrives early April, in the same week than Colorado
  • Nebraska: arrives the second week of July, 13 weeks later than Colorado

Common questions

When do Vesper Sparrows arrive in Colorado?
Vesper Sparrows reach Colorado in early April, are common by the second week of April, peak in the second week of September (10% of checklists), and most are gone by early October.
When do Vesper Sparrows leave Colorado?
Most Vesper Sparrows have left Colorado by early October, when reports fall below half their usual rate. Stragglers are still reported until the second week of October.
When is the best time to see a Vesper Sparrow in Colorado?
The Vesper Sparrow is reported most often in the second week of September, on about 10% of Colorado checklists.
Where in Colorado are Vesper Sparrows seen most often?
By county, Cheyenne County, Lincoln County, and Sedgwick County have the highest peak reporting rates for the Vesper Sparrow (counties with at least 200 checklists).