WhenToBird

Anas platyrhynchos · Anatidae

When Do Mallards Arrive in Colorado?

Adult male Mallard
Photo: euqirneto, CC BY 4.0 via iNaturalist

The Mallard is in Colorado all year. It turns up on about 47% of checklists at its peak (mid April) and on 19% in its quietest week (the second week of July).

When to look

PresentAll year
Peak weekApr 15-21mid April
Quietest weekJul 8-14the second week of July

Best: mid April. Here all year. Peak: on about 47% of Colorado checklists.

  1. Jancommon
  2. Febcommon
  3. Marpeak season
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Julcommon
  8. Augcommon
  9. Sepcommon
  10. Octpeak season
  11. Novpeak season
  12. Decpeak season

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

0%20%40%60%Jan 1-7: 31% of 32254 checklistsJan 8-14: 31% of 23278 checklistsJan 15-21: 31% of 22933 checklistsJan 22-31: 31% of 30856 checklistsFeb 1-7: 32% of 21464 checklistsFeb 8-14: 29% of 22910 checklistsFeb 15-21: 28% of 28739 checklistsFeb 22-28: 36% of 21833 checklistsMar 1-7: 40% of 23066 checklistsMar 8-14: 40% of 23783 checklistsMar 15-21: 42% of 24797 checklistsMar 22-31: 45% of 38439 checklistsApr 1-7: 45% of 31676 checklistsApr 8-14: 46% of 35092 checklistsApr 15-21: 47% of 36778 checklistsApr 22-30: 49% of 50885 checklistsMay 1-7: 45% of 44186 checklistsMay 8-14: 41% of 49011 checklistsMay 15-21: 39% of 40784 checklistsMay 22-31: 34% of 53073 checklistsJun 1-7: 29% of 32432 checklistsJun 8-14: 25% of 29978 checklistsJun 15-21: 22% of 29457 checklistsJun 22-30: 21% of 36072 checklistsJul 1-7: 20% of 28857 checklistsJul 8-14: 18% of 27224 checklistsJul 15-21: 19% of 27629 checklistsJul 22-31: 20% of 37318 checklistsAug 1-7: 22% of 25893 checklistsAug 8-14: 25% of 24870 checklistsAug 15-21: 27% of 24035 checklistsAug 22-31: 29% of 35691 checklistsSep 1-7: 30% of 27068 checklistsSep 8-14: 31% of 26709 checklistsSep 15-21: 30% of 26098 checklistsSep 22-30: 31% of 31550 checklistsOct 1-7: 30% of 24110 checklistsOct 8-14: 33% of 23352 checklistsOct 15-21: 35% of 21895 checklistsOct 22-31: 38% of 28319 checklistsNov 1-7: 40% of 21698 checklistsNov 8-14: 40% of 21061 checklistsNov 15-21: 39% of 19855 checklistsNov 22-30: 38% of 25798 checklistsDec 1-7: 36% of 18626 checklistsDec 8-14: 33% of 19004 checklistsDec 15-21: 31% of 23103 checklistsDec 22-31: 32% 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 the second week of November · 17 checklists that week, 1,323 in all79%
  2. Broomfield CountyBest early April · 433 checklists that week, 16,139 in all75%
  3. Rio Grande CountyBest early April · 91 checklists that week, 4,655 in all68%
  4. Adams CountyBest mid April · 1104 checklists that week, 44,639 in all62%
  5. Larimer CountyBest late April · 6145 checklists that week, 171,224 in all61%
  6. Arapahoe CountyBest late April · 3452 checklists that week, 98,030 in all60%

Best spots

Share of checklists at the peak
  1. West Lake (northeast)Broomfield County, best early April · 22 checklists that week, 948 in all100%
  2. Lake CatamountRoutt County, best late October · 22 checklists that week, 224 in all100%
  3. Eagle Meadows ParkJefferson County, best the second week of April · 31 checklists that week, 134 in all100%
  4. South Platte Pk\ Carson Nature Area (Cooley Lake)Arapahoe County, best the second week of February · 26 checklists that week, 1,101 in all100%

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

Best time of day

In Colorado, the Mallard is most often listed on checklists started between 4 and 6 pm (37% of those checklists).

0%10%20%30%40%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: 31% of 71991 checklists7 am: 31% of 159189 checklists8 am: 34% of 177206 checklists9 am: 35% of 165269 checklists10 am: 33% of 141029 checklists11 am: 33% of 115283 checklists12 pm: 33% of 96068 checklists1 pm: 35% of 89512 checklists2 pm: 36% of 86319 checklists3 pm: 37% of 82496 checklists4 pm: 37% of 71648 checklists5 pm: 37% of 52445 checklists6 pm: 35% 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
January31%31%31%31%
February32%29%28%36%
March40%40%42%45%
April45%46%47%49%
May45%41%39%34%
June29%25%22%21%
July20%18%19%20%
August22%25%27%29%
September30%31%30%31%
October30%33%35%38%
November40%40%39%38%
December36%33%31%32%

Neighboring states

  • Wyoming: all year, most in spring, peaks mid April
  • New Mexico: year-round, peaks early December
  • Utah: year-round, peaks the second week of April
  • Nebraska: all year, most in spring, peaks the second week of April

Common questions

When do Mallards arrive in Colorado?
The Mallard is in Colorado all year. It turns up on about 47% of checklists at its peak (mid April) and on 19% in its quietest week (the second week of July).
When do Mallards leave Colorado?
The Mallard does not leave Colorado: it is reported all year, from 19% of checklists in the second week of July to 47% in mid April.
When is the best time to see a Mallard in Colorado?
The Mallard is reported most often in mid April, on about 47% of Colorado checklists.
Where in Colorado are Mallards seen most often?
By county, Costilla County, Broomfield County, and Rio Grande County have the highest peak reporting rates for the Mallard (counties with at least 200 checklists).