WhenToBird

Nannopterum auritum · Phalacrocoracidae

When Do Double-crested Cormorants Arrive in Iowa?

Adult Double-crested Cormorant
Photo: jubileej, CC0 1.0 via iNaturalist

Double-crested Cormorants are winter birds in Iowa: the first arrive in the second week of March, they are common by mid March, peak in late October (16% of checklists), and most are gone by early December.

When to look

First arrivalsMar 8-14the second week of March
Common byMar 15-21mid March
PeakOct 22-31late October
Most gone byDec 1-7early December

Best: late October. First arrivals the second week of March; most are gone by early December. Peak: on about 16% of Iowa checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marcommon
  4. Aprpeak season
  5. Maycommon
  6. Jununcommon
  7. Juluncommon
  8. Augcommon
  9. Seppeak season
  10. Octpeak season
  11. Novpeak season
  12. Decuncommon

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

0%5%10%15%20%Jan 1-7: 0.2% of 5551 checklistsJan 8-14: 0.1% of 3498 checklistsJan 15-21: 0.1% of 3803 checklistsJan 22-31: 0.1% of 4807 checklistsFeb 1-7: 0.1% of 3613 checklistsFeb 8-14: 0.1% of 4173 checklistsFeb 15-21: 0.1% of 5796 checklistsFeb 22-28: 0.1% of 4394 checklistsMar 1-7: 0.4% of 5295 checklistsMar 8-14: 1.2% of 5679 checklistsMar 15-21: 3.3% of 5418 checklistsMar 22-31: 8.6% of 8613 checklistsApr 1-7: 13% of 6970 checklistsApr 8-14: 15% of 7511 checklistsApr 15-21: 15% of 8321 checklistsApr 22-30: 11% of 11976 checklistsMay 1-7: 8.1% of 11725 checklistsMay 8-14: 5.4% of 12626 checklistsMay 15-21: 4.6% of 9372 checklistsMay 22-31: 4.5% of 10330 checklistsJun 1-7: 3.7% of 5472 checklistsJun 8-14: 3.6% of 4568 checklistsJun 15-21: 3.4% of 3870 checklistsJun 22-30: 3.4% of 4780 checklistsJul 1-7: 4.1% of 4201 checklistsJul 8-14: 3.8% of 3605 checklistsJul 15-21: 3.4% of 3621 checklistsJul 22-31: 5.7% of 5093 checklistsAug 1-7: 6.6% of 3931 checklistsAug 8-14: 8.9% of 3488 checklistsAug 15-21: 9.9% of 3802 checklistsAug 22-31: 10% of 6293 checklistsSep 1-7: 12% of 5328 checklistsSep 8-14: 12% of 4622 checklistsSep 15-21: 13% of 4367 checklistsSep 22-30: 16% of 6086 checklistsOct 1-7: 13% of 4708 checklistsOct 8-14: 15% of 4791 checklistsOct 15-21: 16% of 4429 checklistsOct 22-31: 16% of 5633 checklistsNov 1-7: 15% of 4090 checklistsNov 8-14: 12% of 3416 checklistsNov 15-21: 11% of 3398 checklistsNov 22-30: 7.8% of 4679 checklistsDec 1-7: 3.9% of 3442 checklistsDec 8-14: 2.4% of 3322 checklistsDec 15-21: 0.7% of 4619 checklistsDec 22-31: 0.6% 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.

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Where in Iowa

Best counties

Share of checklists at the peak
  1. Kossuth CountyBest late August · 13 checklists that week, 628 in all51%
  2. Louisa CountyBest mid April · 53 checklists that week, 1,639 in all46%
  3. Mahaska CountyBest late September · 24 checklists that week, 912 in all45%
  4. Shelby CountyBest mid April · 15 checklists that week, 354 in all45%
  5. Jackson CountyBest mid April · 59 checklists that week, 1,765 in all42%
  6. Palo Alto CountyBest mid April · 16 checklists that week, 460 in all42%

Best spots

Share of checklists at the peak
  1. Polk City RefugePolk County, best late September · 22 checklists that week, 705 in all97%
  2. Saylorville Recreation Area (Big Creek)Polk County, best late October · 34 checklists that week, 999 in all91%
  3. Cedar Lake ParkLinn County, best late August · 21 checklists that week, 1,387 in all85%
  4. Hendrickson Marsh Wildlife Management AreaStory County, best mid April · 39 checklists that week, 556 in all84%
  5. Saylorville Recreation Area (northwest)Polk County, best late August · 91 checklists that week, 1,546 in all82%
  6. Saylorville Recreation Area (Rock Creek)Polk County, best late October · 120 checklists that week, 1,401 in all79%

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

Best time of day

In Iowa, the Double-crested Cormorant is most often listed on checklists started between 8 and 10 am (8.2% of those checklists).

0%5%10%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: 7.2% of 11313 checklists7 am: 7.5% of 25717 checklists8 am: 8.5% of 29755 checklists9 am: 7.9% of 28897 checklists10 am: 7.4% of 26343 checklists11 am: 7.4% of 21210 checklists12 pm: 7.9% of 17662 checklists1 pm: 6.7% of 16595 checklists2 pm: 6.1% of 16405 checklists3 pm: 6.3% of 17030 checklists4 pm: 6.7% of 17378 checklists5 pm: 7.8% of 14251 checklists6 pm: 6.3% of 10349 checklists7 pm: 3.5% 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
January0.2%0.1%0.1%0.1%
February0.1%0.1%0.1%0.1%
March0.4%1.2%3.3%8.6%
April13%15%15%11%
May8.1%5.4%4.6%4.5%
June3.7%3.6%3.4%3.4%
July4.1%3.8%3.4%5.7%
August6.6%8.9%9.9%10%
September12%12%13%16%
October13%15%16%16%
November15%12%11%7.8%
December3.9%2.4%0.7%0.6%

Neighboring states

  • Missouri: arrives mid February, 3 weeks earlier than Iowa
  • Wisconsin: arrives late March, 2 weeks later than Iowa
  • Minnesota: arrives mid March, 1 week later than Iowa
  • Illinois: arrives early March, 1 week earlier than Iowa

Common questions

When do Double-crested Cormorants arrive in Iowa?
Double-crested Cormorants are winter birds in Iowa: the first arrive in the second week of March, they are common by mid March, peak in late October (16% of checklists), and most are gone by early December.
When do Double-crested Cormorants leave Iowa?
Most Double-crested Cormorants have left Iowa by early December, when reports fall below half their usual rate. Stragglers are still reported until mid December.
When is the best time to see a Double-crested Cormorant in Iowa?
The Double-crested Cormorant is reported most often in late October, on about 16% of Iowa checklists.
Where in Iowa are Double-crested Cormorants seen most often?
By county, Kossuth County, Louisa County, and Mahaska County have the highest peak reporting rates for the Double-crested Cormorant (counties with at least 200 checklists).