WhenToBird

Passer montanus · Passeridae

When Do Eurasian Tree Sparrows Arrive in Iowa?

Eurasian Tree Sparrows are in Iowa all year, but most are here in winter: numbers build from the second week of October, peak in mid February (6.6% of checklists), and fall back by early April. In the quietest week (the second week of September) they are still on about 2.6% of checklists.

When to look

Numbers buildOct 8-14the second week of October
PeakFeb 15-21mid February
Fall back byApr 1-7early April
FewestSep 8-14the second week of September

Best: mid February. Here all year; numbers build from the second week of October and fall back by early April. Peak: on about 6.6% of Iowa checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marpeak season
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julpeak season
  8. Augcommon
  9. Sepcommon
  10. Octpeak season
  11. Novpeak season
  12. Decpeak season

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

0%2%4%6%8%Jan 1-7: 6.1% of 5551 checklistsJan 8-14: 6.2% of 3498 checklistsJan 15-21: 6.2% of 3803 checklistsJan 22-31: 5.8% of 4807 checklistsFeb 1-7: 6.3% of 3613 checklistsFeb 8-14: 7.1% of 4173 checklistsFeb 15-21: 6.3% of 5796 checklistsFeb 22-28: 6.6% of 4394 checklistsMar 1-7: 6.3% of 5295 checklistsMar 8-14: 5.1% of 5679 checklistsMar 15-21: 5.0% of 5418 checklistsMar 22-31: 5.2% of 8613 checklistsApr 1-7: 4.4% of 6970 checklistsApr 8-14: 4.8% of 7511 checklistsApr 15-21: 4.7% of 8321 checklistsApr 22-30: 5.7% of 11976 checklistsMay 1-7: 5.6% of 11725 checklistsMay 8-14: 5.3% of 12626 checklistsMay 15-21: 4.7% of 9372 checklistsMay 22-31: 5.0% of 10330 checklistsJun 1-7: 5.4% of 5472 checklistsJun 8-14: 4.7% of 4568 checklistsJun 15-21: 4.9% of 3870 checklistsJun 22-30: 5.3% of 4780 checklistsJul 1-7: 4.9% of 4201 checklistsJul 8-14: 5.2% of 3605 checklistsJul 15-21: 5.1% of 3621 checklistsJul 22-31: 4.7% of 5093 checklistsAug 1-7: 3.9% of 3931 checklistsAug 8-14: 4.8% of 3488 checklistsAug 15-21: 3.4% of 3802 checklistsAug 22-31: 3.3% of 6293 checklistsSep 1-7: 2.6% of 5328 checklistsSep 8-14: 2.5% of 4622 checklistsSep 15-21: 2.9% of 4367 checklistsSep 22-30: 3.3% of 6086 checklistsOct 1-7: 4.4% of 4708 checklistsOct 8-14: 4.8% of 4791 checklistsOct 15-21: 5.4% of 4429 checklistsOct 22-31: 5.1% of 5633 checklistsNov 1-7: 6.5% of 4090 checklistsNov 8-14: 6.0% of 3416 checklistsNov 15-21: 5.9% of 3398 checklistsNov 22-30: 5.9% of 4679 checklistsDec 1-7: 6.9% of 3442 checklistsDec 8-14: 7.1% of 3322 checklistsDec 15-21: 6.1% of 4619 checklistsDec 22-31: 6.8% 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. Delaware CountyBest early March · 11 checklists that week, 616 in all65%
  2. Keokuk CountyBest late June · 15 checklists that week, 243 in all51%
  3. Buchanan CountyBest early February · 26 checklists that week, 2,265 in all47%
  4. Louisa CountyBest late October · 28 checklists that week, 1,639 in all45%
  5. Jefferson CountyBest late January · 77 checklists that week, 4,772 in all41%
  6. Washington CountyBest the second week of February · 29 checklists that week, 1,746 in all38%

Best spots

Share of checklists at the peak
  1. Credit Isand ParkScott County, best early June · 21 checklists that week, 777 in all62%
  2. Cedar River Crossing AdditionJohnson County, best mid October · 34 checklists that week, 564 in all59%
  3. Sand Lake City ParkJohnson County, best late June · 29 checklists that week, 2,979 in all55%
  4. Cone Marsh Wildlife Management AreaLouisa County, best late June · 21 checklists that week, 1,002 in all53%
  5. Water Plant ParkJohnson County, best the second week of July · 20 checklists that week, 1,004 in all48%
  6. Chain-o-lakes Wildlife Management AreaLinn County, best early October · 21 checklists that week, 155 in all36%

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

Best time of day

In Iowa, the Eurasian Tree Sparrow is most often listed on checklists started between 6 and 8 am (10% 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: 9.9% of 11313 checklists7 am: 11% of 25717 checklists8 am: 7.3% of 29755 checklists9 am: 5.4% of 28897 checklists10 am: 4.1% of 26343 checklists11 am: 3.8% of 21210 checklists12 pm: 3.7% of 17662 checklists1 pm: 3.4% of 16595 checklists2 pm: 3.0% of 16405 checklists3 pm: 3.5% of 17030 checklists4 pm: 3.5% of 17378 checklists5 pm: 3.4% of 14251 checklists6 pm: 3.4% of 10349 checklists7 pm: 3.8% 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
January6.1%6.2%6.2%5.8%
February6.3%7.1%6.3%6.6%
March6.3%5.1%5.0%5.2%
April4.4%4.8%4.7%5.7%
May5.6%5.3%4.7%5.0%
June5.4%4.7%4.9%5.3%
July4.9%5.2%5.1%4.7%
August3.9%4.8%3.4%3.3%
September2.6%2.5%2.9%3.3%
October4.4%4.8%5.4%5.1%
November6.5%6.0%5.9%5.9%
December6.9%7.1%6.1%6.8%

Neighboring states

  • Missouri: year-round, peaks the second week of February
  • Illinois: arrives late September, 2 weeks earlier than Iowa

Common questions

When do Eurasian Tree Sparrows arrive in Iowa?
Eurasian Tree Sparrows are in Iowa all year, but most are here in winter: numbers build from the second week of October, peak in mid February (6.6% of checklists), and fall back by early April. In the quietest week (the second week of September) they are still on about 2.6% of checklists.
When do Eurasian Tree Sparrows leave Iowa?
Eurasian Tree Sparrows never fully leave Iowa: numbers fall back below half their usual rate by early April, but some are still reported in every week, about 2.6% of checklists at the low.
When is the best time to see a Eurasian Tree Sparrow in Iowa?
The Eurasian Tree Sparrow is reported most often in mid February, on about 6.6% of Iowa checklists.
Where in Iowa are Eurasian Tree Sparrows seen most often?
By county, Delaware County, Keokuk County, and Buchanan County have the highest peak reporting rates for the Eurasian Tree Sparrow (counties with at least 200 checklists).