WhenToBird

Nannopterum auritum · Phalacrocoracidae

When Do Double-crested Cormorants Arrive in Colorado?

Adult Double-crested Cormorant
Photo: jubileej, CC0 1.0 via iNaturalist

Double-crested Cormorants reach Colorado in late February, are common by mid March, peak in late April (20% of checklists), and most are gone by early November.

When to look

First arrivalsFeb 22-28late February
Common byMar 15-21mid March
PeakApr 22-30late April
Most gone byNov 1-7early November

Best: late April. First arrivals late February; most are gone by early November. Peak: on about 20% of Colorado checklists.

  1. Janrare
  2. Febrare
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Augpeak season
  9. Seppeak season
  10. Octcommon
  11. Novuncommon
  12. Decrare

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

0%10%20%30%Jan 1-7: 1.0% of 32254 checklistsJan 8-14: 1.0% of 23278 checklistsJan 15-21: 1.1% of 22933 checklistsJan 22-31: 1.0% of 30856 checklistsFeb 1-7: 0.8% of 21464 checklistsFeb 8-14: 0.7% of 22910 checklistsFeb 15-21: 1.0% of 28739 checklistsFeb 22-28: 1.9% of 21833 checklistsMar 1-7: 3.0% of 23066 checklistsMar 8-14: 4.9% of 23783 checklistsMar 15-21: 7.3% of 24797 checklistsMar 22-31: 11% of 38439 checklistsApr 1-7: 15% of 31676 checklistsApr 8-14: 17% of 35092 checklistsApr 15-21: 18% of 36778 checklistsApr 22-30: 20% of 50885 checklistsMay 1-7: 20% of 44186 checklistsMay 8-14: 18% of 49011 checklistsMay 15-21: 18% of 40784 checklistsMay 22-31: 16% of 53073 checklistsJun 1-7: 15% of 32432 checklistsJun 8-14: 13% of 29978 checklistsJun 15-21: 13% of 29457 checklistsJun 22-30: 13% of 36072 checklistsJul 1-7: 12% of 28857 checklistsJul 8-14: 12% of 27224 checklistsJul 15-21: 12% of 27629 checklistsJul 22-31: 12% of 37318 checklistsAug 1-7: 13% of 25893 checklistsAug 8-14: 14% of 24870 checklistsAug 15-21: 15% of 24035 checklistsAug 22-31: 15% of 35691 checklistsSep 1-7: 15% of 27068 checklistsSep 8-14: 16% of 26709 checklistsSep 15-21: 15% of 26098 checklistsSep 22-30: 13% of 31550 checklistsOct 1-7: 12% of 24110 checklistsOct 8-14: 11% of 23352 checklistsOct 15-21: 11% of 21895 checklistsOct 22-31: 8.7% of 28319 checklistsNov 1-7: 6.7% of 21698 checklistsNov 8-14: 4.8% of 21061 checklistsNov 15-21: 3.3% of 19855 checklistsNov 22-30: 2.4% of 25798 checklistsDec 1-7: 1.8% of 18626 checklistsDec 8-14: 1.4% of 19004 checklistsDec 15-21: 0.9% of 23103 checklistsDec 22-31: 1.0% 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. Adams CountyBest late May · 1578 checklists that week, 44,639 in all47%
  2. Crowley CountyBest late March · 69 checklists that week, 1,883 in all47%
  3. Broomfield CountyBest late May · 514 checklists that week, 16,139 in all46%
  4. Sedgwick CountyBest mid September · 38 checklists that week, 1,168 in all46%
  5. Pueblo CountyBest the second week of April · 668 checklists that week, 26,547 in all45%
  6. Washington CountyBest the second week of August · 37 checklists that week, 2,511 in all41%

Best spots

Share of checklists at the peak
  1. Tabor LakeJefferson County, best the second week of April · 20 checklists that week, 706 in all100%
  2. City Park (Duck Lake)Denver County, best the second week of April · 22 checklists that week, 749 in all100%
  3. Golden PondsBoulder County, best the second week of August · 20 checklists that week, 2,364 in all99%
  4. Platte Canyon Reservoir (Brush Creek)Douglas County, best the second week of July · 21 checklists that week, 1,284 in all98%
  5. North Mills Clarifying PondPueblo County, best the second week of July · 20 checklists that week, 1,694 in all98%
  6. Centennial Park (Big Dry Creek)Arapahoe County, best the second week of September · 20 checklists that week, 1,594 in all98%

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

Best time of day

In Colorado, the Double-crested Cormorant is most often listed on checklists started between 5 and 7 pm (13% of those checklists).

0%5%10%15%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: 14% of 71991 checklists7 am: 12% of 159189 checklists8 am: 12% of 177206 checklists9 am: 11% of 165269 checklists10 am: 10% of 141029 checklists11 am: 9.7% of 115283 checklists12 pm: 9.5% of 96068 checklists1 pm: 9.3% of 89512 checklists2 pm: 9.2% of 86319 checklists3 pm: 9.2% of 82496 checklists4 pm: 11% of 71648 checklists5 pm: 13% of 52445 checklists6 pm: 13% 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
January1.0%1.0%1.1%1.0%
February0.8%0.7%1.0%1.9%
March3.0%4.9%7.3%11%
April15%17%18%20%
May20%18%18%16%
June15%13%13%13%
July12%12%12%12%
August13%14%15%15%
September15%16%15%13%
October12%11%11%8.7%
November6.7%4.8%3.3%2.4%
December1.8%1.4%0.9%1.0%

Neighboring states

  • Wyoming: arrives late March, 4 weeks later than Colorado
  • New Mexico: year-round, peaks early October
  • Utah: arrives early January, 7 weeks earlier than Colorado
  • Nebraska: arrives early March, 1 week later than Colorado

Common questions

When do Double-crested Cormorants arrive in Colorado?
Double-crested Cormorants reach Colorado in late February, are common by mid March, peak in late April (20% of checklists), and most are gone by early November.
When do Double-crested Cormorants leave Colorado?
Most Double-crested Cormorants have left Colorado by early November, when reports fall below half their usual rate. Stragglers are still reported until early December.
When is the best time to see a Double-crested Cormorant in Colorado?
The Double-crested Cormorant is reported most often in late April, on about 20% of Colorado checklists.
Where in Colorado are Double-crested Cormorants seen most often?
By county, Adams County, Crowley County, and Broomfield County have the highest peak reporting rates for the Double-crested Cormorant (counties with at least 200 checklists).