WhenToBird

Passerina caerulea · Cardinalidae

When Do Blue Grosbeaks Arrive in Iowa?

Adult male Blue Grosbeak
Photo: John Rosford, CC BY 4.0 via iNaturalist

Blue Grosbeaks reach Iowa in late May, are common by early June, peak in the second week of August (4.1% of checklists), and most are gone by early September.

When to look

First arrivalsMay 22-31late May
Common byJun 1-7early June
PeakAug 8-14the second week of August
Most gone bySep 1-7early September

Best: the second week of August. First arrivals late May; most are gone by early September. Peak: on about 4.1% of Iowa checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprrare
  5. Mayuncommon
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Sepcommon
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%2%4%6%Jan 1-7: 0% of 5551 checklistsJan 8-14: 0% of 3498 checklistsJan 15-21: 0% of 3803 checklistsJan 22-31: 0% of 4807 checklistsFeb 1-7: 0% of 3613 checklistsFeb 8-14: 0% of 4173 checklistsFeb 15-21: 0% of 5796 checklistsFeb 22-28: 0% of 4394 checklistsMar 1-7: 0% of 5295 checklistsMar 8-14: 0% of 5679 checklistsMar 15-21: 0% of 5418 checklistsMar 22-31: 0% of 8613 checklistsApr 1-7: 0% of 6970 checklistsApr 8-14: 0% of 7511 checklistsApr 15-21: 0% of 8321 checklistsApr 22-30: 0.1% of 11976 checklistsMay 1-7: 0.3% of 11725 checklistsMay 8-14: 0.4% of 12626 checklistsMay 15-21: 0.9% of 9372 checklistsMay 22-31: 1.3% of 10330 checklistsJun 1-7: 1.7% of 5472 checklistsJun 8-14: 2.0% of 4568 checklistsJun 15-21: 2.5% of 3870 checklistsJun 22-30: 1.9% of 4780 checklistsJul 1-7: 2.9% of 4201 checklistsJul 8-14: 2.5% of 3605 checklistsJul 15-21: 3.3% of 3621 checklistsJul 22-31: 3.6% of 5093 checklistsAug 1-7: 4.3% of 3931 checklistsAug 8-14: 4.0% of 3488 checklistsAug 15-21: 4.0% of 3802 checklistsAug 22-31: 2.8% of 6293 checklistsSep 1-7: 1.2% of 5328 checklistsSep 8-14: 0.6% of 4622 checklistsSep 15-21: 0.3% of 4367 checklistsSep 22-30: 0.2% of 6086 checklistsOct 1-7: 0.1% of 4708 checklistsOct 8-14: 0.1% of 4791 checklistsOct 15-21: 0.1% of 4429 checklistsOct 22-31: 0% of 5633 checklistsNov 1-7: 0% of 4090 checklistsNov 8-14: 0% of 3416 checklistsNov 15-21: 0% of 3398 checklistsNov 22-30: 0% of 4679 checklistsDec 1-7: 0% of 3442 checklistsDec 8-14: 0% of 3322 checklistsDec 15-21: 0% of 4619 checklistsDec 22-31: 0% 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. Cherokee CountyBest early August · 14 checklists that week, 360 in all24%
  2. Lyon CountyBest late June · 13 checklists that week, 498 in all20%
  3. Louisa CountyBest the second week of July · 15 checklists that week, 1,639 in all17%
  4. Buena Vista CountyBest late July · 121 checklists that week, 2,846 in all16%
  5. Van Buren CountyBest the second week of August · 17 checklists that week, 1,213 in all15%
  6. Monona CountyBest late August · 26 checklists that week, 655 in all15%

Best spots

Share of checklists at the peak
  1. Tedesco Environmental Learning Corridor (TELC)Story County, best late July · 27 checklists that week, 969 in all51%
  2. Water Plant ParkJohnson County, best early August · 23 checklists that week, 1,004 in all40%
  3. Saylorville Recreation Area (Corydon (historical))Polk County, best the second week of August · 35 checklists that week, 1,186 in all34%
  4. Coralville Recreation Area (southwest)Johnson County, best late May · 40 checklists that week, 228 in all34%
  5. Saylorville Recreation Area (Big Creek)Polk County, best the second week of August · 37 checklists that week, 999 in all29%
  6. Cone Marsh Wildlife Management AreaLouisa County, best late June · 21 checklists that week, 1,002 in all21%

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

Best time of day

In Iowa, the Blue Grosbeak is most often listed on checklists started between 6 and 8 pm (1.4% of those checklists).

0%1%2%3%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: 2.2% of 11313 checklists7 am: 1.0% of 25717 checklists8 am: 0.8% of 29755 checklists9 am: 0.7% of 28897 checklists10 am: 0.6% of 26343 checklists11 am: 0.6% of 21210 checklists12 pm: 0.5% of 17662 checklists1 pm: 0.4% of 16595 checklists2 pm: 0.3% of 16405 checklists3 pm: 0.3% of 17030 checklists4 pm: 0.3% of 17378 checklists5 pm: 0.8% of 14251 checklists6 pm: 1.4% of 10349 checklists7 pm: 1.5% 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%0%0%0%
February0%0%0%0%
March0%0%0%0%
April0%0%0%0.1%
May0.3%0.4%0.9%1.3%
June1.7%2.0%2.5%1.9%
July2.9%2.5%3.3%3.6%
August4.3%4.0%4.0%2.8%
September1.2%0.6%0.3%0.2%
October0.1%0.1%0.1%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Missouri: arrives mid April, 5 weeks earlier than Iowa
  • Illinois: arrives late April, 4 weeks earlier than Iowa
  • Nebraska: arrives the second week of May, 2 weeks earlier than Iowa
  • Kansas: arrives late April, 4 weeks earlier than Iowa

Common questions

When do Blue Grosbeaks arrive in Iowa?
Blue Grosbeaks reach Iowa in late May, are common by early June, peak in the second week of August (4.1% of checklists), and most are gone by early September.
When do Blue Grosbeaks leave Iowa?
Most Blue Grosbeaks have left Iowa by early September, when reports fall below half their usual rate.
When is the best time to see a Blue Grosbeak in Iowa?
The Blue Grosbeak is reported most often in the second week of August, on about 4.1% of Iowa checklists.
Where in Iowa are Blue Grosbeaks seen most often?
By county, Cherokee County, Lyon County, and Louisa County have the highest peak reporting rates for the Blue Grosbeak (counties with at least 200 checklists).