WhenToBird

Lophodytes cucullatus · Anatidae

When Do Hooded Mergansers Arrive in Iowa?

Adult male Hooded Merganser
Photo: Justin Flint, CC BY 4.0 via iNaturalist

Hooded Mergansers are winter birds in Iowa: the first arrive in late October, they are common by early November, peak in mid March (13% of checklists), and most are gone by late April.

When to look

First arrivalsOct 22-31late October
Common byNov 1-7early November
PeakMar 15-21mid March
Most gone byApr 22-30late April

Best: mid March. First arrivals late October; most are gone by late April. Peak: on about 13% of Iowa checklists.

  1. Januncommon
  2. Febcommon
  3. Marpeak season
  4. Aprcommon
  5. Mayuncommon
  6. Jununcommon
  7. Julrare
  8. Augrare
  9. Sepnot usually seen
  10. Octuncommon
  11. Novcommon
  12. Deccommon

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

0%5%10%15%Jan 1-7: 3.0% of 5551 checklistsJan 8-14: 2.9% of 3498 checklistsJan 15-21: 1.8% of 3803 checklistsJan 22-31: 2.5% of 4807 checklistsFeb 1-7: 2.2% of 3613 checklistsFeb 8-14: 2.1% of 4173 checklistsFeb 15-21: 2.4% of 5796 checklistsFeb 22-28: 6.0% of 4394 checklistsMar 1-7: 10% of 5295 checklistsMar 8-14: 13% of 5679 checklistsMar 15-21: 14% of 5418 checklistsMar 22-31: 12% of 8613 checklistsApr 1-7: 8.7% of 6970 checklistsApr 8-14: 5.3% of 7511 checklistsApr 15-21: 5.3% of 8321 checklistsApr 22-30: 3.5% of 11976 checklistsMay 1-7: 2.3% of 11725 checklistsMay 8-14: 1.7% of 12626 checklistsMay 15-21: 1.6% of 9372 checklistsMay 22-31: 2.0% of 10330 checklistsJun 1-7: 2.0% of 5472 checklistsJun 8-14: 1.9% of 4568 checklistsJun 15-21: 1.4% of 3870 checklistsJun 22-30: 1.7% of 4780 checklistsJul 1-7: 1.6% of 4201 checklistsJul 8-14: 1.6% of 3605 checklistsJul 15-21: 0.9% of 3621 checklistsJul 22-31: 1.2% of 5093 checklistsAug 1-7: 0.7% of 3931 checklistsAug 8-14: 0.4% of 3488 checklistsAug 15-21: 0.5% of 3802 checklistsAug 22-31: 0.4% of 6293 checklistsSep 1-7: 0.3% of 5328 checklistsSep 8-14: 0.2% of 4622 checklistsSep 15-21: 0.2% of 4367 checklistsSep 22-30: 0.2% of 6086 checklistsOct 1-7: 0.2% of 4708 checklistsOct 8-14: 0.3% of 4791 checklistsOct 15-21: 0.5% of 4429 checklistsOct 22-31: 1.6% of 5633 checklistsNov 1-7: 5.2% of 4090 checklistsNov 8-14: 9.4% of 3416 checklistsNov 15-21: 7.8% of 3398 checklistsNov 22-30: 9.7% of 4679 checklistsDec 1-7: 9.2% of 3442 checklistsDec 8-14: 5.7% of 3322 checklistsDec 15-21: 3.6% of 4619 checklistsDec 22-31: 2.9% of 5113 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 Iowa 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.

Embed this map on your site

Where in Iowa

Best counties

Share of checklists at the peak
  1. Worth CountyBest late March · 10 checklists that week, 333 in all41%
  2. Palo Alto CountyBest mid March · 12 checklists that week, 460 in all40%
  3. Hancock CountyBest mid March · 11 checklists that week, 449 in all38%
  4. Guthrie CountyBest mid March · 22 checklists that week, 1,167 in all37%
  5. Buena Vista CountyBest mid March · 67 checklists that week, 2,846 in all36%
  6. Lee CountyBest late November · 26 checklists that week, 1,488 in all35%

Best spots

Share of checklists at the peak
  1. Hendrickson Marsh Wildlife Management Area (east)Marshall County, best the second week of March · 22 checklists that week, 250 in all63%
  2. Swan LakeJohnson County, best mid March · 24 checklists that week, 687 in all61%
  3. Saylorville Recreation AreaPolk County, best mid November · 50 checklists that week, 1,723 in all61%
  4. Hendrickson Marsh Wildlife Management AreaStory County, best late March · 34 checklists that week, 556 in all57%
  5. Saylorville Recreation Area (Camp Dodge)Polk County, best early December · 43 checklists that week, 690 in all54%
  6. Saylorville Recreation Area (Rock Creek)Polk County, best early December · 82 checklists that week, 1,401 in all52%

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

Best time of day

In Iowa, the Hooded Merganser is most often listed on checklists started between 9 and 11 am (4.1% of those checklists).

0%2%4%6%12 am: too few checklists (96) to judge1 am: too few checklists (99) to judge2 am: too few checklists (67) to judge3 am: too few checklists (82) to judge4 am: too few checklists (201) to judge5 am: too few checklists (1888) to judge6 am: 2.6% of 11313 checklists7 am: 3.3% of 25717 checklists8 am: 3.8% of 29755 checklists9 am: 4.0% of 28897 checklists10 am: 4.2% of 26343 checklists11 am: 3.9% of 21210 checklists12 pm: 4.2% of 17662 checklists1 pm: 3.8% of 16595 checklists2 pm: 3.9% of 16405 checklists3 pm: 3.5% of 17030 checklists4 pm: 3.9% of 17378 checklists5 pm: 4.0% of 14251 checklists6 pm: 3.0% of 10349 checklists7 pm: 2.2% of 6233 checklists8 pm: too few checklists (2002) to judge9 pm: too few checklists (392) to judge10 pm: too few checklists (186) to judge11 pm: too few checklists (87) 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
January3.0%2.9%1.8%2.5%
February2.2%2.1%2.4%6.0%
March10%13%14%12%
April8.7%5.3%5.3%3.5%
May2.3%1.7%1.6%2.0%
June2.0%1.9%1.4%1.7%
July1.6%1.6%0.9%1.2%
August0.7%0.4%0.5%0.4%
September0.3%0.2%0.2%0.2%
October0.2%0.3%0.5%1.6%
November5.2%9.4%7.8%9.7%
December9.2%5.7%3.6%2.9%

Neighboring states

  • Missouri: arrives late October, in the same week than Iowa
  • Wisconsin: arrives mid February, 15 weeks later than Iowa
  • Minnesota: arrives late February, 16 weeks later than Iowa
  • Illinois: arrives mid October, 1 week earlier than Iowa

Common questions

When do Hooded Mergansers arrive in Iowa?
Hooded Mergansers are winter birds in Iowa: the first arrive in late October, they are common by early November, peak in mid March (13% of checklists), and most are gone by late April.
When do Hooded Mergansers leave Iowa?
Most Hooded Mergansers have left Iowa by late April, when reports fall below half their usual rate. Stragglers are still reported until mid July.
When is the best time to see a Hooded Merganser in Iowa?
The Hooded Merganser is reported most often in mid March, on about 13% of Iowa checklists.
Where in Iowa are Hooded Mergansers seen most often?
By county, Worth County, Palo Alto County, and Hancock County have the highest peak reporting rates for the Hooded Merganser (counties with at least 200 checklists).