WhenToBird

Sialia mexicana · Turdidae

When Do Western Bluebirds Arrive in Colorado?

Adult male Western Bluebird
Photo: sprcrkwild, CC BY 4.0 via iNaturalist

Western Bluebirds reach Colorado in early March, are common by the second week of March, peak in the second week of April (3.8% of checklists), and most are gone by mid October.

When to look

First arrivalsMar 1-7early March
Common byMar 8-14the second week of March
PeakApr 8-14the second week of April
Most gone byOct 15-21mid October

Best: the second week of April. First arrivals early March; most are gone by mid October. Peak: on about 3.8% of Colorado checklists.

  1. Januncommon
  2. Febuncommon
  3. Marpeak season
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octpeak season
  11. Novuncommon
  12. Decuncommon

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

0%2%4%6%Jan 1-7: 0.5% of 32254 checklistsJan 8-14: 0.7% of 23278 checklistsJan 15-21: 0.5% of 22933 checklistsJan 22-31: 0.7% of 30856 checklistsFeb 1-7: 0.5% of 21464 checklistsFeb 8-14: 0.6% of 22910 checklistsFeb 15-21: 0.7% of 28739 checklistsFeb 22-28: 0.8% of 21833 checklistsMar 1-7: 0.9% of 23066 checklistsMar 8-14: 1.3% of 23783 checklistsMar 15-21: 2.5% of 24797 checklistsMar 22-31: 3.6% of 38439 checklistsApr 1-7: 4.0% of 31676 checklistsApr 8-14: 3.5% of 35092 checklistsApr 15-21: 4.0% of 36778 checklistsApr 22-30: 3.0% of 50885 checklistsMay 1-7: 2.6% of 44186 checklistsMay 8-14: 2.8% of 49011 checklistsMay 15-21: 3.0% of 40784 checklistsMay 22-31: 3.2% of 53073 checklistsJun 1-7: 3.2% of 32432 checklistsJun 8-14: 3.7% of 29978 checklistsJun 15-21: 3.2% of 29457 checklistsJun 22-30: 3.7% of 36072 checklistsJul 1-7: 3.6% of 28857 checklistsJul 8-14: 3.1% of 27224 checklistsJul 15-21: 3.0% of 27629 checklistsJul 22-31: 2.8% of 37318 checklistsAug 1-7: 2.8% of 25893 checklistsAug 8-14: 2.8% of 24870 checklistsAug 15-21: 3.0% of 24035 checklistsAug 22-31: 3.1% of 35691 checklistsSep 1-7: 3.0% of 27068 checklistsSep 8-14: 3.3% of 26709 checklistsSep 15-21: 3.2% of 26098 checklistsSep 22-30: 3.6% of 31550 checklistsOct 1-7: 3.9% of 24110 checklistsOct 8-14: 4.0% of 23352 checklistsOct 15-21: 2.5% of 21895 checklistsOct 22-31: 1.2% of 28319 checklistsNov 1-7: 0.8% of 21698 checklistsNov 8-14: 0.5% of 21061 checklistsNov 15-21: 0.5% of 19855 checklistsNov 22-30: 0.4% of 25798 checklistsDec 1-7: 0.5% of 18626 checklistsDec 8-14: 0.6% of 19004 checklistsDec 15-21: 0.9% of 23103 checklistsDec 22-31: 0.7% 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. Elbert CountyBest the second week of June · 182 checklists that week, 5,660 in all30%
  2. Custer CountyBest mid April · 34 checklists that week, 3,017 in all26%
  3. Archuleta CountyBest early October · 166 checklists that week, 10,365 in all22%
  4. Teller CountyBest the second week of April · 179 checklists that week, 11,258 in all20%
  5. Montezuma CountyBest late September · 472 checklists that week, 15,992 in all18%
  6. Las Animas CountyBest mid April · 61 checklists that week, 3,491 in all16%

Best spots

Share of checklists at the peak
  1. Genesee ParkJefferson County, best mid September · 26 checklists that week, 1,068 in all79%
  2. Walker Ranch ParkBoulder County, best late June · 31 checklists that week, 365 in all78%
  3. Pueblo Mountain ParkPueblo County, best the second week of May · 20 checklists that week, 454 in all73%
  4. Mount Falcon ParkJefferson County, best early September · 20 checklists that week, 597 in all72%
  5. Dupont Fee TitleDouglas County, best the second week of May · 24 checklists that week, 547 in all65%

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

Best time of day

In Colorado, the Western Bluebird is most often listed on checklists started between 6 and 8 am (3.1% of those checklists).

0%1%2%3%4%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: 3.2% of 71991 checklists7 am: 3.0% of 159189 checklists8 am: 2.9% of 177206 checklists9 am: 2.6% of 165269 checklists10 am: 2.4% of 141029 checklists11 am: 2.1% of 115283 checklists12 pm: 1.9% of 96068 checklists1 pm: 1.9% of 89512 checklists2 pm: 1.9% of 86319 checklists3 pm: 2.0% of 82496 checklists4 pm: 2.0% of 71648 checklists5 pm: 2.2% of 52445 checklists6 pm: 2.2% 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
January0.5%0.7%0.5%0.7%
February0.5%0.6%0.7%0.8%
March0.9%1.3%2.5%3.6%
April4.0%3.5%4.0%3.0%
May2.6%2.8%3.0%3.2%
June3.2%3.7%3.2%3.7%
July3.6%3.1%3.0%2.8%
August2.8%2.8%3.0%3.1%
September3.0%3.3%3.2%3.6%
October3.9%4.0%2.5%1.2%
November0.8%0.5%0.5%0.4%
December0.5%0.6%0.9%0.7%

Neighboring states

  • New Mexico: year-round, peaks late October
  • Utah: arrives mid January, 6 weeks earlier than Colorado
  • Arizona: arrives late October, 17 weeks earlier than Colorado
  • Montana: arrives early March, in the same week than Colorado

Common questions

When do Western Bluebirds arrive in Colorado?
Western Bluebirds reach Colorado in early March, are common by the second week of March, peak in the second week of April (3.8% of checklists), and most are gone by mid October.
When do Western Bluebirds leave Colorado?
Most Western Bluebirds have left Colorado by mid October, when reports fall below half their usual rate. Stragglers are still reported until late October.
When is the best time to see a Western Bluebird in Colorado?
The Western Bluebird is reported most often in the second week of April, on about 3.8% of Colorado checklists.
Where in Colorado are Western Bluebirds seen most often?
By county, Elbert County, Custer County, and Archuleta County have the highest peak reporting rates for the Western Bluebird (counties with at least 200 checklists).