WhenToBird

Mergus merganser · Anatidae

When Do Common Mergansers Arrive in Arizona?

Adult female Common Merganser
Photo: Christoph Moning, CC BY 4.0 via iNaturalist

Common Mergansers are winter birds in Arizona: the first arrive in late November, they are common by the second week of December, peak in mid January (5.5% of checklists), and most are gone by late March.

When to look

First arrivalsNov 22-30late November
Common byDec 8-14the second week of December
PeakJan 15-21mid January
Most gone byMar 22-31late March

Best: mid January. First arrivals late November; most are gone by late March. Peak: on about 5.5% of Arizona checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marcommon
  4. Apruncommon
  5. Mayrare
  6. Junnot usually seen
  7. Julnot usually seen
  8. Augnot usually seen
  9. Seprare
  10. Octrare
  11. Novuncommon
  12. Deccommon

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

0%2%4%6%Jan 1-7: 4.4% of 34758 checklistsJan 8-14: 5.2% of 29835 checklistsJan 15-21: 5.7% of 29279 checklistsJan 22-31: 5.6% of 39716 checklistsFeb 1-7: 4.8% of 27299 checklistsFeb 8-14: 4.9% of 28703 checklistsFeb 15-21: 4.1% of 35357 checklistsFeb 22-28: 4.2% of 29889 checklistsMar 1-7: 3.7% of 29932 checklistsMar 8-14: 3.0% of 32982 checklistsMar 15-21: 2.4% of 34731 checklistsMar 22-31: 1.9% of 50213 checklistsApr 1-7: 1.2% of 35788 checklistsApr 8-14: 1.0% of 38087 checklistsApr 15-21: 0.8% of 41520 checklistsApr 22-30: 0.4% of 55218 checklistsMay 1-7: 0.3% of 39688 checklistsMay 8-14: 0.3% of 39398 checklistsMay 15-21: 0.2% of 29562 checklistsMay 22-31: 0.2% of 36774 checklistsJun 1-7: 0.2% of 21313 checklistsJun 8-14: 0.2% of 19129 checklistsJun 15-21: 0.2% of 17922 checklistsJun 22-30: 0.1% of 21188 checklistsJul 1-7: 0.1% of 17325 checklistsJul 8-14: 0.1% of 16463 checklistsJul 15-21: 0.1% of 18642 checklistsJul 22-31: 0.1% of 31215 checklistsAug 1-7: 0.1% of 28163 checklistsAug 8-14: 0.1% of 31329 checklistsAug 15-21: 0.1% of 23878 checklistsAug 22-31: 0.2% of 28508 checklistsSep 1-7: 0.3% of 20878 checklistsSep 8-14: 0.3% of 19671 checklistsSep 15-21: 0.5% of 19859 checklistsSep 22-30: 0.4% of 25179 checklistsOct 1-7: 0.4% of 19420 checklistsOct 8-14: 0.4% of 21925 checklistsOct 15-21: 0.5% of 20995 checklistsOct 22-31: 0.5% of 29258 checklistsNov 1-7: 0.6% of 21269 checklistsNov 8-14: 0.8% of 22753 checklistsNov 15-21: 1.0% of 21982 checklistsNov 22-30: 1.1% of 29475 checklistsDec 1-7: 1.7% of 20810 checklistsDec 8-14: 2.2% of 22229 checklistsDec 15-21: 2.5% of 25148 checklistsDec 22-31: 3.1% of 39567 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 Arizona 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 Arizona

Best counties

Share of checklists at the peak
  1. Graham CountyBest mid February · 189 checklists that week, 9,876 in all31%
  2. Navajo CountyBest late February · 256 checklists that week, 18,838 in all14%
  3. Yavapai CountyBest mid January · 1712 checklists that week, 83,606 in all13%
  4. Coconino CountyBest mid March · 1597 checklists that week, 90,870 in all13%
  5. Mohave CountyBest mid January · 390 checklists that week, 18,083 in all13%
  6. Apache CountyBest late February · 119 checklists that week, 12,931 in all12%

Best spots

Share of checklists at the peak
  1. Bottomless PitCoconino County, best early February · 50 checklists that week, 2,433 in all97%
  2. Roper Lake State ParkGraham County, best mid February · 21 checklists that week, 640 in all92%
  3. Roper Lake and LandGraham County, best mid January · 38 checklists that week, 1,238 in all91%
  4. Thunderbird ParkMaricopa County, best the second week of January · 27 checklists that week, 840 in all90%
  5. Little Stopsign CoveMohave County, best late January · 30 checklists that week, 178 in all86%

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

Best time of day

In Arizona, the Common Merganser is most often listed on checklists started between 1 and 3 pm (2.3% of those checklists).

0%1%2%3%12 am: too few checklists (488) to judge1 am: too few checklists (503) to judge2 am: too few checklists (489) to judge3 am: too few checklists (735) to judge4 am: too few checklists (4115) to judge5 am: 0.2% of 38350 checklists6 am: 0.4% of 118786 checklists7 am: 1.3% of 183415 checklists8 am: 1.9% of 187346 checklists9 am: 2.1% of 151342 checklists10 am: 2.0% of 124522 checklists11 am: 2.1% of 97088 checklists12 pm: 2.1% of 78110 checklists1 pm: 2.2% of 73059 checklists2 pm: 2.3% of 68912 checklists3 pm: 2.1% of 68060 checklists4 pm: 1.9% of 69387 checklists5 pm: 1.3% of 52951 checklists6 pm: 0.5% of 31061 checklists7 pm: too few checklists (16076) to judge8 pm: too few checklists (5352) to judge9 pm: too few checklists (2369) to judge10 pm: too few checklists (1100) to judge11 pm: too few checklists (604) 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
January4.4%5.2%5.7%5.6%
February4.8%4.9%4.1%4.2%
March3.7%3.0%2.4%1.9%
April1.2%1.0%0.8%0.4%
May0.3%0.3%0.2%0.2%
June0.2%0.2%0.2%0.1%
July0.1%0.1%0.1%0.1%
August0.1%0.1%0.1%0.2%
September0.3%0.3%0.5%0.4%
October0.4%0.4%0.5%0.5%
November0.6%0.8%1.0%1.1%
December1.7%2.2%2.5%3.1%

Neighboring states

  • New Mexico: arrives early November, 3 weeks earlier than Arizona
  • Nevada: arrives early September, 11 weeks earlier than Arizona
  • Utah: arrives mid September, 9 weeks earlier than Arizona
  • California: arrives mid October, 5 weeks earlier than Arizona

Common questions

When do Common Mergansers arrive in Arizona?
Common Mergansers are winter birds in Arizona: the first arrive in late November, they are common by the second week of December, peak in mid January (5.5% of checklists), and most are gone by late March.
When do Common Mergansers leave Arizona?
Most Common Mergansers have left Arizona by late March, when reports fall below half their usual rate. Stragglers are still reported until early April.
When is the best time to see a Common Merganser in Arizona?
The Common Merganser is reported most often in mid January, on about 5.5% of Arizona checklists.
Where in Arizona are Common Mergansers seen most often?
By county, Graham County, Navajo County, and Yavapai County have the highest peak reporting rates for the Common Merganser (counties with at least 200 checklists).