WhenToBird

Aechmophorus occidentalis · Podicipedidae

When Do Western Grebes Arrive in Colorado?

Adult Western Grebe
Photo: Craig K, CC BY 4.0 via iNaturalist

Western Grebes are winter birds in Colorado: the first arrive in late March, they are common by the second week of April, peak in early November (12% of checklists), and most are gone by early December.

When to look

First arrivalsMar 22-31late March
Common byApr 8-14the second week of April
PeakNov 1-7early November
Most gone byDec 1-7early December

Best: early November. First arrivals late March; most are gone by early December. Peak: on about 12% of Colorado checklists.

  1. Janrare
  2. Febrare
  3. Marrare
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Juluncommon
  8. Auguncommon
  9. Sepcommon
  10. Octpeak season
  11. Novpeak season
  12. Decuncommon

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

0%5%10%15%Jan 1-7: 1.5% of 32254 checklistsJan 8-14: 1.0% of 23278 checklistsJan 15-21: 1.0% of 22933 checklistsJan 22-31: 0.8% of 30856 checklistsFeb 1-7: 0.4% of 21464 checklistsFeb 8-14: 0.4% of 22910 checklistsFeb 15-21: 0.3% of 28739 checklistsFeb 22-28: 0.4% of 21833 checklistsMar 1-7: 0.4% of 23066 checklistsMar 8-14: 0.5% of 23783 checklistsMar 15-21: 0.6% of 24797 checklistsMar 22-31: 1.2% of 38439 checklistsApr 1-7: 2.5% of 31676 checklistsApr 8-14: 4.7% of 35092 checklistsApr 15-21: 9.0% of 36778 checklistsApr 22-30: 12% of 50885 checklistsMay 1-7: 9.6% of 44186 checklistsMay 8-14: 7.5% of 49011 checklistsMay 15-21: 6.6% of 40784 checklistsMay 22-31: 5.6% of 53073 checklistsJun 1-7: 5.1% of 32432 checklistsJun 8-14: 3.6% of 29978 checklistsJun 15-21: 3.0% of 29457 checklistsJun 22-30: 2.6% of 36072 checklistsJul 1-7: 2.5% of 28857 checklistsJul 8-14: 2.0% of 27224 checklistsJul 15-21: 2.1% of 27629 checklistsJul 22-31: 2.4% of 37318 checklistsAug 1-7: 3.0% of 25893 checklistsAug 8-14: 3.6% of 24870 checklistsAug 15-21: 3.8% of 24035 checklistsAug 22-31: 3.9% of 35691 checklistsSep 1-7: 4.1% of 27068 checklistsSep 8-14: 4.8% of 26709 checklistsSep 15-21: 5.4% of 26098 checklistsSep 22-30: 5.8% of 31550 checklistsOct 1-7: 6.0% of 24110 checklistsOct 8-14: 7.0% of 23352 checklistsOct 15-21: 9.9% of 21895 checklistsOct 22-31: 12% of 28319 checklistsNov 1-7: 12% of 21698 checklistsNov 8-14: 11% of 21061 checklistsNov 15-21: 7.1% of 19855 checklistsNov 22-30: 5.9% of 25798 checklistsDec 1-7: 3.6% of 18626 checklistsDec 8-14: 2.4% of 19004 checklistsDec 15-21: 1.5% of 23103 checklistsDec 22-31: 1.5% 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. Costilla CountyBest late April · 40 checklists that week, 1,323 in all57%
  2. Delta CountyBest late April · 318 checklists that week, 6,509 in all53%
  3. Crowley CountyBest early November · 16 checklists that week, 1,883 in all45%
  4. Kiowa CountyBest the second week of November · 58 checklists that week, 3,854 in all42%
  5. Washington CountyBest the second week of November · 15 checklists that week, 2,511 in all40%
  6. Huerfano CountyBest late November · 42 checklists that week, 3,008 in all37%

Best spots

Share of checklists at the peak
  1. Ireland Reservoir Number FiveWeld County, best late April · 20 checklists that week, 168 in all100%
  2. Fossil Creek Reservoir Natural AreaLarimer County, best late July · 33 checklists that week, 1,582 in all98%
  3. Smith ReservoirCostilla County, best early May · 20 checklists that week, 432 in all97%
  4. Walden ReservoirJackson County, best late June · 29 checklists that week, 546 in all96%
  5. Totten LakeMontezuma County, best late October · 29 checklists that week, 994 in all95%
  6. Third CreekAdams County, best late October · 32 checklists that week, 298 in all94%

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

Best time of day

In Colorado, the Western Grebe is most often listed on checklists started between 11 am and 1 pm (4.9% of those checklists).

0%2%4%6%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: 4.1% of 71991 checklists7 am: 3.8% of 159189 checklists8 am: 4.4% of 177206 checklists9 am: 4.7% of 165269 checklists10 am: 4.7% of 141029 checklists11 am: 5.0% of 115283 checklists12 pm: 4.8% of 96068 checklists1 pm: 4.8% of 89512 checklists2 pm: 4.8% of 86319 checklists3 pm: 4.5% of 82496 checklists4 pm: 4.6% of 71648 checklists5 pm: 4.9% of 52445 checklists6 pm: 4.5% 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
January1.5%1.0%1.0%0.8%
February0.4%0.4%0.3%0.4%
March0.4%0.5%0.6%1.2%
April2.5%4.7%9.0%12%
May9.6%7.5%6.6%5.6%
June5.1%3.6%3.0%2.6%
July2.5%2.0%2.1%2.4%
August3.0%3.6%3.8%3.9%
September4.1%4.8%5.4%5.8%
October6.0%7.0%9.9%12%
November12%11%7.1%5.9%
December3.6%2.4%1.5%1.5%

Neighboring states

  • Wyoming: arrives the second week of April, 2 weeks later than Colorado
  • New Mexico: arrives mid March, 1 week earlier than Colorado
  • Utah: arrives mid March, 1 week earlier than Colorado
  • Nebraska: arrives early August, 17 weeks later than Colorado

Common questions

When do Western Grebes arrive in Colorado?
Western Grebes are winter birds in Colorado: the first arrive in late March, they are common by the second week of April, peak in early November (12% of checklists), and most are gone by early December.
When do Western Grebes leave Colorado?
Most Western Grebes have left Colorado by early December, when reports fall below half their usual rate. Stragglers are still reported until the second week of January.
When is the best time to see a Western Grebe in Colorado?
The Western Grebe is reported most often in early November, on about 12% of Colorado checklists.
Where in Colorado are Western Grebes seen most often?
By county, Costilla County, Delta County, and Crowley County have the highest peak reporting rates for the Western Grebe (counties with at least 200 checklists).