WhenToBird

Passerella iliaca · Passerellidae

When Do Fox Sparrows Arrive in Colorado?

Adult Fox Sparrow
Photo: Kevin Krebs, CC BY 4.0 via iNaturalist

Fox Sparrows arrive in Colorado in mid May, peak in early July (1.6% of checklists), and most are gone by early August.

When to look

First arrivalsMay 15-21mid May
Common byMay 15-21mid May
PeakJul 1-7early July
Most gone byAug 1-7early August

Best: early July. First arrivals mid May; most are gone by early August. Peak: on about 1.6% of Colorado checklists.

  1. Januncommon
  2. Febrare
  3. Marrare
  4. Apruncommon
  5. Maycommon
  6. Junpeak season
  7. Julpeak season
  8. Auguncommon
  9. Seprare
  10. Octrare
  11. Novrare
  12. Decuncommon

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

0%0.5%1%1.5%2%Jan 1-7: 0.3% of 32254 checklistsJan 8-14: 0.3% of 23278 checklistsJan 15-21: 0.2% of 22933 checklistsJan 22-31: 0.2% of 30856 checklistsFeb 1-7: 0.1% of 21464 checklistsFeb 8-14: 0.1% of 22910 checklistsFeb 15-21: 0.1% of 28739 checklistsFeb 22-28: 0.1% 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: 0.3% of 31676 checklistsApr 8-14: 0.5% of 35092 checklistsApr 15-21: 0.5% of 36778 checklistsApr 22-30: 0.5% of 50885 checklistsMay 1-7: 0.4% of 44186 checklistsMay 8-14: 0.3% of 49011 checklistsMay 15-21: 0.4% of 40784 checklistsMay 22-31: 0.7% of 53073 checklistsJun 1-7: 1.0% of 32432 checklistsJun 8-14: 1.2% of 29978 checklistsJun 15-21: 1.4% of 29457 checklistsJun 22-30: 1.5% of 36072 checklistsJul 1-7: 1.6% of 28857 checklistsJul 8-14: 1.5% of 27224 checklistsJul 15-21: 1.3% of 27629 checklistsJul 22-31: 0.7% of 37318 checklistsAug 1-7: 0.4% of 25893 checklistsAug 8-14: 0.3% of 24870 checklistsAug 15-21: 0.2% of 24035 checklistsAug 22-31: 0.2% of 35691 checklistsSep 1-7: 0.2% of 27068 checklistsSep 8-14: 0.2% of 26709 checklistsSep 15-21: 0.1% of 26098 checklistsSep 22-30: 0.1% of 31550 checklistsOct 1-7: 0.1% of 24110 checklistsOct 8-14: 0.1% of 23352 checklistsOct 15-21: 0.1% 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: 0.1% of 19004 checklistsDec 15-21: 0.3% of 23103 checklistsDec 22-31: 0.2% 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. San Juan CountyBest mid June · 103 checklists that week, 2,012 in all18%
  2. Hinsdale CountyBest early May · 13 checklists that week, 2,303 in all17%
  3. Pitkin CountyBest mid April · 324 checklists that week, 15,513 in all13%
  4. Gunnison CountyBest mid June · 526 checklists that week, 9,894 in all10%
  5. Dolores CountyBest mid June · 27 checklists that week, 2,000 in all10%
  6. Eagle CountyBest early June · 365 checklists that week, 15,893 in all9.5%

Best spots

Share of checklists at the peak
  1. Black Canyon of the Gunnison National ParkMontrose County, best early April · 33 checklists that week, 303 in all55%
  2. Hallam LakePitkin County, best late April · 38 checklists that week, 1,206 in all49%
  3. GothicGunnison County, best late May · 24 checklists that week, 441 in all37%
  4. State Forest State ParkJackson County, best early August · 24 checklists that week, 748 in all33%
  5. Brainard LakeBoulder County, best early July · 31 checklists that week, 512 in all30%
  6. Yampa River PreserveRoutt County, best early June · 22 checklists that week, 203 in all28%

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

Best time of day

In Colorado, the Fox Sparrow is most often listed on checklists started between 6 and 8 am (0.6% of those checklists).

0%0.5%1%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: 0.7% of 71991 checklists7 am: 0.6% of 159189 checklists8 am: 0.6% of 177206 checklists9 am: 0.5% of 165269 checklists10 am: 0.4% of 141029 checklists11 am: 0.4% of 115283 checklists12 pm: 0.3% of 96068 checklists1 pm: 0.3% of 89512 checklists2 pm: 0.3% of 86319 checklists3 pm: 0.3% of 82496 checklists4 pm: 0.2% of 71648 checklists5 pm: 0.2% of 52445 checklists6 pm: 0.3% 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
January0.3%0.3%0.2%0.2%
February0.1%0.1%0.1%0.1%
March0.1%0.1%0.1%0.1%
April0.3%0.5%0.5%0.5%
May0.4%0.3%0.4%0.7%
June1.0%1.2%1.4%1.5%
July1.6%1.5%1.3%0.7%
August0.4%0.3%0.2%0.2%
September0.2%0.2%0.1%0.1%
October0.1%0.1%0.1%0.1%
November0.1%0.1%0.1%0.1%
December0.1%0.1%0.3%0.2%

Neighboring states

  • Wyoming: arrives mid April, 4 weeks earlier than Colorado
  • Utah: arrives early April, 6 weeks earlier than Colorado
  • Nebraska: arrives early October, 18 weeks later than Colorado
  • South Dakota: arrives late September, 17 weeks later than Colorado

Common questions

When do Fox Sparrows arrive in Colorado?
Fox Sparrows arrive in Colorado in mid May, peak in early July (1.6% of checklists), and most are gone by early August.
When do Fox Sparrows leave Colorado?
Most Fox Sparrows have left Colorado by early August, when reports fall below half their usual rate.
When is the best time to see a Fox Sparrow in Colorado?
The Fox Sparrow is reported most often in early July, on about 1.6% of Colorado checklists.
Where in Colorado are Fox Sparrows seen most often?
By county, San Juan County, Hinsdale County, and Pitkin County have the highest peak reporting rates for the Fox Sparrow (counties with at least 200 checklists).