WhenToBird

Toxostoma rufum · Mimidae

When Do Brown Thrashers Arrive in Iowa?

Adult Brown Thrasher
Photo: northerly, CC BY 4.0 via iNaturalist

Brown Thrashers reach Iowa in early April, are common by the second week of April, peak in early May (17% of checklists), and most are gone by late September.

When to look

First arrivalsApr 1-7early April
Common byApr 8-14the second week of April
PeakMay 1-7early May
Most gone bySep 22-30late September

Best: early May. First arrivals early April; most are gone by late September. Peak: on about 17% of Iowa checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marrare
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Sepuncommon
  10. Octuncommon
  11. Novnot usually seen
  12. Decnot usually seen

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

0%5%10%15%20%Jan 1-7: 0.1% 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% of 4173 checklistsFeb 15-21: 0.1% of 5796 checklistsFeb 22-28: 0.1% of 4394 checklistsMar 1-7: 0% of 5295 checklistsMar 8-14: 0.1% of 5679 checklistsMar 15-21: 0.1% of 5418 checklistsMar 22-31: 0.2% of 8613 checklistsApr 1-7: 2.3% of 6970 checklistsApr 8-14: 7.1% of 7511 checklistsApr 15-21: 12% of 8321 checklistsApr 22-30: 18% of 11976 checklistsMay 1-7: 18% of 11725 checklistsMay 8-14: 15% of 12626 checklistsMay 15-21: 13% of 9372 checklistsMay 22-31: 14% of 10330 checklistsJun 1-7: 13% of 5472 checklistsJun 8-14: 13% of 4568 checklistsJun 15-21: 13% of 3870 checklistsJun 22-30: 12% of 4780 checklistsJul 1-7: 11% of 4201 checklistsJul 8-14: 8.9% of 3605 checklistsJul 15-21: 7.3% of 3621 checklistsJul 22-31: 5.2% of 5093 checklistsAug 1-7: 3.5% of 3931 checklistsAug 8-14: 2.6% of 3488 checklistsAug 15-21: 2.3% of 3802 checklistsAug 22-31: 3.0% of 6293 checklistsSep 1-7: 3.7% of 5328 checklistsSep 8-14: 5.0% of 4622 checklistsSep 15-21: 7.4% of 4367 checklistsSep 22-30: 5.6% of 6086 checklistsOct 1-7: 2.2% of 4708 checklistsOct 8-14: 1.1% of 4791 checklistsOct 15-21: 0.1% of 4429 checklistsOct 22-31: 0.1% of 5633 checklistsNov 1-7: 0.1% of 4090 checklistsNov 8-14: 0.1% of 3416 checklistsNov 15-21: 0.1% of 3398 checklistsNov 22-30: 0.1% of 4679 checklistsDec 1-7: 0.1% of 3442 checklistsDec 8-14: 0.1% of 3322 checklistsDec 15-21: 0.2% of 4619 checklistsDec 22-31: 0.1% 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. Monroe CountyBest early June · 16 checklists that week, 257 in all50%
  2. Louisa CountyBest early July · 18 checklists that week, 1,639 in all47%
  3. Ringgold CountyBest early May · 47 checklists that week, 1,141 in all47%
  4. Pocahontas CountyBest early May · 31 checklists that week, 735 in all46%
  5. Madison CountyBest the second week of June · 51 checklists that week, 2,941 in all45%
  6. Clarke CountyBest late April · 22 checklists that week, 459 in all44%

Best spots

Share of checklists at the peak
  1. Brenton ArboretumDallas County, best the second week of May · 22 checklists that week, 426 in all78%
  2. Robison Wildlife AcresStory County, best the second week of May · 23 checklists that week, 203 in all63%
  3. Cone Marsh Wildlife Management AreaLouisa County, best late June · 21 checklists that week, 1,002 in all63%
  4. Hendrickson Marsh Wildlife Management AreaStory County, best late May · 20 checklists that week, 556 in all62%
  5. Coralville Recreation Area (southwest)Johnson County, best late May · 40 checklists that week, 228 in all61%
  6. Dale Maffit ReservoirDallas County, best early May · 23 checklists that week, 457 in all57%

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

Best time of day

In Iowa, the Brown Thrasher is most often listed on checklists started between 6 and 8 am (11% of those checklists).

0%5%10%15%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: 14% of 11313 checklists7 am: 9.9% of 25717 checklists8 am: 7.3% of 29755 checklists9 am: 5.9% of 28897 checklists10 am: 5.2% of 26343 checklists11 am: 4.5% of 21210 checklists12 pm: 4.5% of 17662 checklists1 pm: 3.6% of 16595 checklists2 pm: 3.5% of 16405 checklists3 pm: 3.7% of 17030 checklists4 pm: 4.3% of 17378 checklists5 pm: 5.6% of 14251 checklists6 pm: 6.8% of 10349 checklists7 pm: 6.3% 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
January0.1%0.1%0.1%0.1%
February0.1%0%0.1%0.1%
March0%0.1%0.1%0.2%
April2.3%7.1%12%18%
May18%15%13%14%
June13%13%13%12%
July11%8.9%7.3%5.2%
August3.5%2.6%2.3%3.0%
September3.7%5.0%7.4%5.6%
October2.2%1.1%0.1%0.1%
November0.1%0.1%0.1%0.1%
December0.1%0.1%0.2%0.1%

Neighboring states

  • Missouri: arrives the second week of March, 3 weeks earlier than Iowa
  • Wisconsin: arrives early April, in the same week than Iowa
  • Minnesota: arrives mid April, 2 weeks later than Iowa
  • Illinois: arrives mid March, 2 weeks earlier than Iowa

Common questions

When do Brown Thrashers arrive in Iowa?
Brown Thrashers reach Iowa in early April, are common by the second week of April, peak in early May (17% of checklists), and most are gone by late September.
When do Brown Thrashers leave Iowa?
Most Brown Thrashers have left Iowa by late September, when reports fall below half their usual rate. Stragglers are still reported until the second week of October.
When is the best time to see a Brown Thrasher in Iowa?
The Brown Thrasher is reported most often in early May, on about 17% of Iowa checklists.
Where in Iowa are Brown Thrashers seen most often?
By county, Monroe County, Louisa County, and Ringgold County have the highest peak reporting rates for the Brown Thrasher (counties with at least 200 checklists).