WhenToBird

Quiscalus quiscula · Icteridae

When Do Common Grackles Arrive in Colorado?

Adult Common Grackle
Photo: Derek Spencer, CC BY 4.0 via iNaturalist

Common Grackles reach Colorado in mid March, are common by early April, peak in the second week of May (36% of checklists), and most are gone by mid July.

When to look

First arrivalsMar 15-21mid March
Common byApr 1-7early April
PeakMay 8-14the second week of May
Most gone byJul 15-21mid July

Best: the second week of May. First arrivals mid March; most are gone by mid July. Peak: on about 36% of Colorado checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Maruncommon
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Sepuncommon
  10. Octuncommon
  11. Novrare
  12. Decnot usually seen

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

0%10%20%30%40%Jan 1-7: 0.1% of 32254 checklistsJan 8-14: 0.1% of 23278 checklistsJan 15-21: 0.1% of 22933 checklistsJan 22-31: 0.1% 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: 0.3% of 23783 checklistsMar 15-21: 0.8% of 24797 checklistsMar 22-31: 7.1% of 38439 checklistsApr 1-7: 19% of 31676 checklistsApr 8-14: 26% of 35092 checklistsApr 15-21: 30% of 36778 checklistsApr 22-30: 35% of 50885 checklistsMay 1-7: 37% of 44186 checklistsMay 8-14: 35% of 49011 checklistsMay 15-21: 35% of 40784 checklistsMay 22-31: 33% of 53073 checklistsJun 1-7: 29% of 32432 checklistsJun 8-14: 26% of 29978 checklistsJun 15-21: 24% of 29457 checklistsJun 22-30: 23% of 36072 checklistsJul 1-7: 20% of 28857 checklistsJul 8-14: 15% of 27224 checklistsJul 15-21: 13% of 27629 checklistsJul 22-31: 11% of 37318 checklistsAug 1-7: 10% of 25893 checklistsAug 8-14: 9.4% of 24870 checklistsAug 15-21: 8.8% of 24035 checklistsAug 22-31: 6.9% of 35691 checklistsSep 1-7: 5.8% of 27068 checklistsSep 8-14: 5.6% of 26709 checklistsSep 15-21: 6.2% of 26098 checklistsSep 22-30: 7.8% of 31550 checklistsOct 1-7: 7.7% of 24110 checklistsOct 8-14: 7.9% of 23352 checklistsOct 15-21: 6.3% of 21895 checklistsOct 22-31: 3.4% of 28319 checklistsNov 1-7: 1.4% of 21698 checklistsNov 8-14: 0.6% of 21061 checklistsNov 15-21: 0.4% of 19855 checklistsNov 22-30: 0.2% of 25798 checklistsDec 1-7: 0.2% of 18626 checklistsDec 8-14: 0.2% 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. Phillips CountyBest early June · 21 checklists that week, 1,052 in all84%
  2. Prowers CountyBest the second week of June · 140 checklists that week, 11,307 in all81%
  3. Washington CountyBest early June · 47 checklists that week, 2,511 in all77%
  4. Morgan CountyBest mid June · 100 checklists that week, 5,181 in all73%
  5. Broomfield CountyBest early June · 212 checklists that week, 16,139 in all71%
  6. Sedgwick CountyBest early June · 38 checklists that week, 1,168 in all67%

Best spots

Share of checklists at the peak
  1. North Mills Clarifying PondPueblo County, best mid June · 29 checklists that week, 1,694 in all97%
  2. Last ChanceWashington County, best mid May · 37 checklists that week, 368 in all97%
  3. Heron Pond/Heller Open SpaceDenver County, best late April · 70 checklists that week, 924 in all97%
  4. Big Dry Creek Open SpaceJefferson County, best early May · 23 checklists that week, 103 in all96%
  5. Waneka Lake ParkBoulder County, best early July · 118 checklists that week, 6,926 in all96%

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

Best time of day

In Colorado, the Common Grackle is most often listed on checklists started between 6 and 8 am (19% of those checklists).

0%10%20%30%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: 23% of 71991 checklists7 am: 17% of 159189 checklists8 am: 15% of 177206 checklists9 am: 13% of 165269 checklists10 am: 11% of 141029 checklists11 am: 9.9% of 115283 checklists12 pm: 9.7% of 96068 checklists1 pm: 9.5% of 89512 checklists2 pm: 9.3% of 86319 checklists3 pm: 10% of 82496 checklists4 pm: 13% of 71648 checklists5 pm: 18% of 52445 checklists6 pm: 20% 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
January0.1%0.1%0.1%0.1%
February0.1%0.1%0.1%0.1%
March0.1%0.3%0.8%7.1%
April19%26%30%35%
May37%35%35%33%
June29%26%24%23%
July20%15%13%11%
August10%9.4%8.8%6.9%
September5.8%5.6%6.2%7.8%
October7.7%7.9%6.3%3.4%
November1.4%0.6%0.4%0.2%
December0.2%0.2%0.1%0.1%

Neighboring states

  • Wyoming: arrives late March, 1 week later than Colorado
  • New Mexico: arrives early April, 2 weeks later than Colorado
  • Nebraska: arrives early March, 2 weeks earlier than Colorado
  • South Dakota: arrives early March, 2 weeks earlier than Colorado

Common questions

When do Common Grackles arrive in Colorado?
Common Grackles reach Colorado in mid March, are common by early April, peak in the second week of May (36% of checklists), and most are gone by mid July.
When do Common Grackles leave Colorado?
Most Common Grackles have left Colorado by mid July, when reports fall below half their usual rate. Stragglers are still reported until late October.
When is the best time to see a Common Grackle in Colorado?
The Common Grackle is reported most often in the second week of May, on about 36% of Colorado checklists.
Where in Colorado are Common Grackles seen most often?
By county, Phillips County, Prowers County, and Washington County have the highest peak reporting rates for the Common Grackle (counties with at least 200 checklists).