WhenToBird

Nannopterum brasilianum · Phalacrocoracidae

When Do Neotropic Cormorants Arrive in Oklahoma?

Adult Neotropic Cormorant
Photo: Ricard Busquets Reverte, CC BY 4.0 via iNaturalist

Neotropic Cormorants arrive in Oklahoma in the second week of March, peak in the second week of August (1.3% of checklists), and most are gone by the second week of September.

When to look

First arrivalsMar 8-14the second week of March
Common byMar 8-14the second week of March
PeakAug 8-14the second week of August
Most gone bySep 8-14the second week of September

Best: the second week of August. First arrivals the second week of March; most are gone by the second week of September. Peak: on about 1.3% of Oklahoma checklists.

  1. Janrare
  2. Febrare
  3. Marcommon
  4. Aprcommon
  5. Maypeak season
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Sepcommon
  10. Octrare
  11. Novrare
  12. Decrare

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

0%0.5%1%1.5%Jan 1-7: 0% of 6087 checklistsJan 8-14: 0% of 4350 checklistsJan 15-21: 0.1% of 4381 checklistsJan 22-31: 0.1% of 6165 checklistsFeb 1-7: 0.1% of 4259 checklistsFeb 8-14: 0.1% of 4589 checklistsFeb 15-21: 0.1% of 7001 checklistsFeb 22-28: 0% of 4482 checklistsMar 1-7: 0.1% of 4724 checklistsMar 8-14: 0.8% of 4571 checklistsMar 15-21: 0.4% of 4393 checklistsMar 22-31: 0.9% of 7544 checklistsApr 1-7: 0.8% of 5967 checklistsApr 8-14: 0.5% of 6543 checklistsApr 15-21: 0.9% of 7366 checklistsApr 22-30: 0.8% of 10618 checklistsMay 1-7: 1.0% of 8835 checklistsMay 8-14: 0.9% of 8247 checklistsMay 15-21: 1.2% of 6081 checklistsMay 22-31: 1.0% of 7283 checklistsJun 1-7: 0.8% of 4256 checklistsJun 8-14: 0.8% of 3774 checklistsJun 15-21: 0.9% of 3541 checklistsJun 22-30: 0.8% of 4159 checklistsJul 1-7: 0.8% of 3209 checklistsJul 8-14: 1.1% of 2916 checklistsJul 15-21: 0.7% of 2861 checklistsJul 22-31: 0.9% of 4146 checklistsAug 1-7: 1.2% of 3043 checklistsAug 8-14: 1.2% of 2839 checklistsAug 15-21: 1.3% of 3014 checklistsAug 22-31: 0.6% of 4759 checklistsSep 1-7: 0.6% of 3861 checklistsSep 8-14: 0.3% of 3748 checklistsSep 15-21: 0.4% of 3569 checklistsSep 22-30: 0.2% of 4830 checklistsOct 1-7: 0.1% of 3809 checklistsOct 8-14: 0.2% of 4142 checklistsOct 15-21: 0.2% of 3705 checklistsOct 22-31: 0.1% of 4738 checklistsNov 1-7: 0.1% of 3823 checklistsNov 8-14: 0.1% of 3849 checklistsNov 15-21: 0.1% of 3722 checklistsNov 22-30: 0.1% of 4795 checklistsDec 1-7: 0.1% of 3324 checklistsDec 8-14: 0.1% of 3574 checklistsDec 15-21: 0.1% of 3884 checklistsDec 22-31: 0.1% of 5774 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 Oklahoma 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 Oklahoma

Best counties

Share of checklists at the peak
  1. McCurtain CountyBest the second week of August · 26 checklists that week, 2,908 in all15%
  2. Tillman CountyBest early July · 13 checklists that week, 1,199 in all14%
  3. Jefferson CountyBest late September · 12 checklists that week, 620 in all13%
  4. Alfalfa CountyBest the second week of August · 41 checklists that week, 3,843 in all11%
  5. Bryan CountyBest early June · 20 checklists that week, 1,517 in all9.1%
  6. Marshall CountyBest the second week of April · 15 checklists that week, 590 in all5.4%

Best spots

Share of checklists at the peak
  1. Red SloughMcCurtain County, best early May · 50 checklists that week, 492 in all46%
  2. Lake HefnerOklahoma County, best late July · 32 checklists that week, 2,749 in all28%
  3. Boomer Lake ParkPayne County, best mid May · 124 checklists that week, 3,723 in all26%
  4. Lake Hefner (Lansbrook Lake)Oklahoma County, best early August · 27 checklists that week, 743 in all23%
  5. Lake Hefner (southeast 2)Oklahoma County, best early May · 33 checklists that week, 432 in all20%
  6. Lake YaholaTulsa County, best the second week of August · 33 checklists that week, 1,291 in all14%

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

Best time of day

In Oklahoma, the Neotropic Cormorant is most often listed on checklists started between 6 and 8 am (0.8% of those checklists).

0%0.5%1%12 am: too few checklists (91) to judge1 am: too few checklists (65) to judge2 am: too few checklists (73) to judge3 am: too few checklists (73) to judge4 am: too few checklists (100) to judge5 am: too few checklists (647) to judge6 am: 0.9% of 8353 checklists7 am: 0.8% of 24509 checklists8 am: 0.5% of 27848 checklists9 am: 0.5% of 25316 checklists10 am: 0.4% of 21161 checklists11 am: 0.6% of 18730 checklists12 pm: 0.4% of 16097 checklists1 pm: 0.4% of 14028 checklists2 pm: 0.4% of 13599 checklists3 pm: 0.4% of 14228 checklists4 pm: 0.4% of 14597 checklists5 pm: 0.5% of 12125 checklists6 pm: 0.5% of 9337 checklists7 pm: 0.5% of 6944 checklists8 pm: too few checklists (2403) to judge9 pm: too few checklists (459) to judge10 pm: too few checklists (226) to judge11 pm: too few checklists (141) 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%0%0.1%0.1%
February0.1%0.1%0.1%0%
March0.1%0.8%0.4%0.9%
April0.8%0.5%0.9%0.8%
May1.0%0.9%1.2%1.0%
June0.8%0.8%0.9%0.8%
July0.8%1.1%0.7%0.9%
August1.2%1.2%1.3%0.6%
September0.6%0.3%0.4%0.2%
October0.1%0.2%0.2%0.1%
November0.1%0.1%0.1%0.1%
December0.1%0.1%0.1%0.1%

Neighboring states

  • Texas: year-round, peaks mid April
  • Louisiana: year-round, peaks late August
  • New Mexico: arrives late December, 10 weeks earlier than Oklahoma
  • Mississippi: arrives early July, 15 weeks later than Oklahoma

Common questions

When do Neotropic Cormorants arrive in Oklahoma?
Neotropic Cormorants arrive in Oklahoma in the second week of March, peak in the second week of August (1.3% of checklists), and most are gone by the second week of September.
When do Neotropic Cormorants leave Oklahoma?
Most Neotropic Cormorants have left Oklahoma by the second week of September, when reports fall below half their usual rate.
When is the best time to see a Neotropic Cormorant in Oklahoma?
The Neotropic Cormorant is reported most often in the second week of August, on about 1.3% of Oklahoma checklists.
Where in Oklahoma are Neotropic Cormorants seen most often?
By county, McCurtain County, Tillman County, and Jefferson County have the highest peak reporting rates for the Neotropic Cormorant (counties with at least 200 checklists).