WhenToBird

Spizelloides arborea · Passerellidae

When Do American Tree Sparrows Arrive in Wyoming?

Adult American Tree Sparrow
Photo: Michael, CC BY 4.0 via iNaturalist

American Tree Sparrows are winter birds in Wyoming: they arrive in mid October, peak in early March (6.2% of checklists), and most are gone by late March.

When to look

First arrivalsOct 15-21mid October
Common byOct 15-21mid October
PeakMar 1-7early March
Most gone byMar 22-31late March

Best: early March. First arrivals mid October; most are gone by late March. Peak: on about 6.2% of Wyoming checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marpeak season
  4. Apruncommon
  5. Maynot usually seen
  6. Junnot usually seen
  7. Julnot usually seen
  8. Augnot usually seen
  9. Sepnot usually seen
  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 2543 checklistsJan 8-14: 5.0% of 2114 checklistsJan 15-21: 5.7% of 1984 checklistsJan 22-31: 5.0% of 2605 checklistsFeb 1-7: 6.0% of 1940 checklistsFeb 8-14: 5.4% of 1954 checklistsFeb 15-21: 5.7% of 2575 checklistsFeb 22-28: 6.1% of 1932 checklistsMar 1-7: 6.4% of 2486 checklistsMar 8-14: 6.1% of 2535 checklistsMar 15-21: 5.5% of 2726 checklistsMar 22-31: 2.9% of 4349 checklistsApr 1-7: 2.6% of 3300 checklistsApr 8-14: 1.1% of 3500 checklistsApr 15-21: 0.4% of 3701 checklistsApr 22-30: 0.1% of 5887 checklistsMay 1-7: 0.1% of 5341 checklistsMay 8-14: 0.1% of 6910 checklistsMay 15-21: 0% of 6884 checklistsMay 22-31: 0% of 10652 checklistsJun 1-7: 0% of 6807 checklistsJun 8-14: 0% of 6714 checklistsJun 15-21: 0% of 6708 checklistsJun 22-30: 0% of 8160 checklistsJul 1-7: 0% of 5755 checklistsJul 8-14: 0% of 5379 checklistsJul 15-21: 0% of 5299 checklistsJul 22-31: 0% of 6830 checklistsAug 1-7: 0% of 4581 checklistsAug 8-14: 0% of 4625 checklistsAug 15-21: 0% of 4466 checklistsAug 22-31: 0% of 6562 checklistsSep 1-7: 0% of 4543 checklistsSep 8-14: 0% of 4652 checklistsSep 15-21: 0% of 4186 checklistsSep 22-30: 0.1% of 5301 checklistsOct 1-7: 0.1% of 3248 checklistsOct 8-14: 0.5% of 3010 checklistsOct 15-21: 2.4% of 2624 checklistsOct 22-31: 5.7% of 3170 checklistsNov 1-7: 6.1% of 2110 checklistsNov 8-14: 6.2% of 2153 checklistsNov 15-21: 5.2% of 1971 checklistsNov 22-30: 4.8% of 2136 checklistsDec 1-7: 5.5% of 1646 checklistsDec 8-14: 5.1% of 1609 checklistsDec 15-21: 7.0% of 1954 checklistsDec 22-31: 5.5% of 2392 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 Wyoming 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 Wyoming

Best counties

Share of checklists at the peak
  1. Goshen CountyBest the second week of December · 19 checklists that week, 1,920 in all35%
  2. Carbon CountyBest late January · 59 checklists that week, 6,429 in all31%
  3. Weston CountyBest early November · 30 checklists that week, 2,297 in all29%
  4. Johnson CountyBest early November · 96 checklists that week, 5,977 in all26%
  5. Crook CountyBest the second week of March · 42 checklists that week, 3,915 in all24%
  6. Platte CountyBest early November · 12 checklists that week, 1,645 in all23%

Best spots

Share of checklists at the peak
  1. Healy ReservoirJohnson County, best the second week of November · 24 checklists that week, 406 in all51%
  2. Optomist ParkAlbany County, best early December · 33 checklists that week, 2,101 in all46%
  3. L A K ReservoirWeston County, best late October · 26 checklists that week, 531 in all34%
  4. Lake de SmetJohnson County, best early November · 24 checklists that week, 435 in all27%
  5. Hudson DrawFremont County, best the second week of January · 64 checklists that week, 2,803 in all17%

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

Best time of day

In Wyoming, the American Tree Sparrow is most often listed on checklists started between 8 and 10 am (2.2% of those checklists).

0%1%2%3%12 am: too few checklists (59) to judge1 am: too few checklists (76) to judge2 am: too few checklists (86) to judge3 am: too few checklists (79) to judge4 am: too few checklists (326) to judge5 am: too few checklists (2271) to judge6 am: 0.2% of 8808 checklists7 am: 1.5% of 18458 checklists8 am: 2.4% of 22143 checklists9 am: 2.0% of 21499 checklists10 am: 1.7% of 19425 checklists11 am: 1.7% of 16017 checklists12 pm: 1.5% of 13868 checklists1 pm: 1.6% of 12984 checklists2 pm: 1.5% of 12605 checklists3 pm: 1.6% of 11821 checklists4 pm: 1.4% of 10571 checklists5 pm: 0.6% of 8746 checklists6 pm: 0.4% of 6707 checklists7 pm: 0.1% of 4890 checklists8 pm: too few checklists (2323) to judge9 pm: too few checklists (554) to judge10 pm: too few checklists (134) to judge11 pm: too few checklists (59) 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%5.0%5.7%5.0%
February6.0%5.4%5.7%6.1%
March6.4%6.1%5.5%2.9%
April2.6%1.1%0.4%0.1%
May0.1%0.1%0%0%
June0%0%0%0%
July0%0%0%0%
August0%0%0%0%
September0%0%0%0.1%
October0.1%0.5%2.4%5.7%
November6.1%6.2%5.2%4.8%
December5.5%5.1%7.0%5.5%

Neighboring states

  • Colorado: arrives mid October, in the same week than Wyoming
  • Utah: arrives early November, 2 weeks later than Wyoming
  • Montana: arrives early October, 2 weeks earlier than Wyoming
  • Idaho: arrives late October, 1 week later than Wyoming

Common questions

When do American Tree Sparrows arrive in Wyoming?
American Tree Sparrows are winter birds in Wyoming: they arrive in mid October, peak in early March (6.2% of checklists), and most are gone by late March.
When do American Tree Sparrows leave Wyoming?
Most American Tree Sparrows have left Wyoming by late March, when reports fall below half their usual rate. Stragglers are still reported until the second week of April.
When is the best time to see a American Tree Sparrow in Wyoming?
The American Tree Sparrow is reported most often in early March, on about 6.2% of Wyoming checklists.
Where in Wyoming are American Tree Sparrows seen most often?
By county, Goshen County, Carbon County, and Weston County have the highest peak reporting rates for the American Tree Sparrow (counties with at least 200 checklists).