WhenToBird

Mareca strepera · Anatidae

When Do Gadwalls Arrive in Colorado?

Adult Gadwall
Photo: Anne Parsons, CC0 1.0 via iNaturalist

Gadwalls reach Colorado in late August, are common by early October, peak in the second week of April (26% of checklists), and most are gone by mid May.

When to look

First arrivalsAug 22-31late August
Common byOct 1-7early October
PeakApr 8-14the second week of April
Most gone byMay 15-21mid May

Best: the second week of April. First arrivals late August; most are gone by mid May. Peak: on about 26% of Colorado checklists.

  1. Jancommon
  2. Febcommon
  3. Marpeak season
  4. Aprpeak season
  5. Maycommon
  6. Jununcommon
  7. Julrare
  8. Augrare
  9. Sepuncommon
  10. Octcommon
  11. Novpeak season
  12. Deccommon

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

0%10%20%30%Jan 1-7: 11% of 32254 checklistsJan 8-14: 11% of 23278 checklistsJan 15-21: 11% of 22933 checklistsJan 22-31: 11% of 30856 checklistsFeb 1-7: 11% of 21464 checklistsFeb 8-14: 10% of 22910 checklistsFeb 15-21: 9.5% of 28739 checklistsFeb 22-28: 14% of 21833 checklistsMar 1-7: 17% of 23066 checklistsMar 8-14: 20% of 23783 checklistsMar 15-21: 23% of 24797 checklistsMar 22-31: 25% of 38439 checklistsApr 1-7: 27% of 31676 checklistsApr 8-14: 26% of 35092 checklistsApr 15-21: 26% of 36778 checklistsApr 22-30: 25% of 50885 checklistsMay 1-7: 19% of 44186 checklistsMay 8-14: 13% of 49011 checklistsMay 15-21: 9.0% of 40784 checklistsMay 22-31: 6.0% of 53073 checklistsJun 1-7: 4.6% of 32432 checklistsJun 8-14: 3.0% of 29978 checklistsJun 15-21: 2.6% of 29457 checklistsJun 22-30: 2.4% of 36072 checklistsJul 1-7: 2.1% of 28857 checklistsJul 8-14: 1.7% of 27224 checklistsJul 15-21: 1.7% of 27629 checklistsJul 22-31: 1.7% of 37318 checklistsAug 1-7: 1.5% of 25893 checklistsAug 8-14: 2.2% of 24870 checklistsAug 15-21: 2.3% of 24035 checklistsAug 22-31: 2.9% of 35691 checklistsSep 1-7: 3.3% of 27068 checklistsSep 8-14: 4.3% of 26709 checklistsSep 15-21: 5.1% of 26098 checklistsSep 22-30: 6.9% of 31550 checklistsOct 1-7: 9.0% of 24110 checklistsOct 8-14: 12% of 23352 checklistsOct 15-21: 16% of 21895 checklistsOct 22-31: 19% of 28319 checklistsNov 1-7: 20% of 21698 checklistsNov 8-14: 20% of 21061 checklistsNov 15-21: 17% of 19855 checklistsNov 22-30: 16% of 25798 checklistsDec 1-7: 15% of 18626 checklistsDec 8-14: 12% of 19004 checklistsDec 15-21: 11% of 23103 checklistsDec 22-31: 11% 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. Rio Grande CountyBest early April · 91 checklists that week, 4,655 in all58%
  2. Costilla CountyBest late April · 40 checklists that week, 1,323 in all50%
  3. Phillips CountyBest the second week of April · 24 checklists that week, 1,052 in all49%
  4. Crowley CountyBest mid March · 14 checklists that week, 1,883 in all48%
  5. Adams CountyBest late March · 1457 checklists that week, 44,639 in all47%
  6. Huerfano CountyBest late November · 42 checklists that week, 3,008 in all43%

Best spots

Share of checklists at the peak
  1. West LakeJefferson County, best early January · 149 checklists that week, 1,835 in all99%
  2. Mary Carter GreenwayArapahoe County, best the second week of December · 22 checklists that week, 906 in all99%
  3. Sands Lake State Wildlife AreaChaffee County, best mid February · 20 checklists that week, 1,345 in all98%
  4. Lake Pueblo State Park (Rock Canyon)Pueblo County, best early January · 22 checklists that week, 607 in all98%
  5. Heron Pond/Heller Open SpaceDenver County, best early April · 21 checklists that week, 924 in all97%

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

Best time of day

In Colorado, the Gadwall is most often listed on checklists started between 1 and 3 pm (14% 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: 7.4% of 71991 checklists7 am: 8.6% of 159189 checklists8 am: 11% of 177206 checklists9 am: 13% of 165269 checklists10 am: 13% of 141029 checklists11 am: 13% of 115283 checklists12 pm: 13% of 96068 checklists1 pm: 14% of 89512 checklists2 pm: 14% of 86319 checklists3 pm: 14% of 82496 checklists4 pm: 13% of 71648 checklists5 pm: 12% of 52445 checklists6 pm: 9.1% 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
January11%11%11%11%
February11%10%9.5%14%
March17%20%23%25%
April27%26%26%25%
May19%13%9.0%6.0%
June4.6%3.0%2.6%2.4%
July2.1%1.7%1.7%1.7%
August1.5%2.2%2.3%2.9%
September3.3%4.3%5.1%6.9%
October9.0%12%16%19%
November20%20%17%16%
December15%12%11%11%

Neighboring states

  • Wyoming: arrives late February, 24 weeks earlier than Colorado
  • New Mexico: arrives early September, 1 week later than Colorado
  • Utah: arrives late August, in the same week than Colorado
  • Nebraska: arrives mid August, 1 week earlier than Colorado

Common questions

When do Gadwalls arrive in Colorado?
Gadwalls reach Colorado in late August, are common by early October, peak in the second week of April (26% of checklists), and most are gone by mid May.
When do Gadwalls leave Colorado?
Most Gadwalls have left Colorado by mid May, when reports fall below half their usual rate. Stragglers are still reported until the second week of June.
When is the best time to see a Gadwall in Colorado?
The Gadwall is reported most often in the second week of April, on about 26% of Colorado checklists.
Where in Colorado are Gadwalls seen most often?
By county, Rio Grande County, Costilla County, and Phillips County have the highest peak reporting rates for the Gadwall (counties with at least 200 checklists).