WhenToBird

Spizelloides arborea · Passerellidae

When Do American Tree Sparrows Arrive in Idaho?

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

American Tree Sparrows are winter birds in Idaho: they arrive in late October, peak in the second week of January (1.6% of checklists), and most are gone by mid March.

When to look

First arrivalsOct 22-31late October
Common byOct 22-31late October
PeakJan 8-14the second week of January
Most gone byMar 15-21mid March

Best: the second week of January. First arrivals late October; most are gone by mid March. Peak: on about 1.6% of Idaho checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marcommon
  4. Apruncommon
  5. Maynot usually seen
  6. Junnot usually seen
  7. Julnot usually seen
  8. Augnot usually seen
  9. Sepnot usually seen
  10. Octcommon
  11. Novpeak season
  12. Decpeak season

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

0%0.5%1%1.5%2%Jan 1-7: 1.7% of 9357 checklistsJan 8-14: 1.4% of 6408 checklistsJan 15-21: 1.7% of 6358 checklistsJan 22-31: 1.2% of 8601 checklistsFeb 1-7: 1.2% of 5611 checklistsFeb 8-14: 1.4% of 6090 checklistsFeb 15-21: 0.9% of 7973 checklistsFeb 22-28: 0.9% of 5866 checklistsMar 1-7: 0.9% of 6144 checklistsMar 8-14: 1.0% of 6456 checklistsMar 15-21: 1.0% of 6786 checklistsMar 22-31: 0.5% of 9539 checklistsApr 1-7: 0.2% of 7202 checklistsApr 8-14: 0.1% of 7608 checklistsApr 15-21: 0.1% of 8069 checklistsApr 22-30: 0.1% of 10973 checklistsMay 1-7: 0% of 9481 checklistsMay 8-14: 0% of 11318 checklistsMay 15-21: 0.1% of 9141 checklistsMay 22-31: 0% of 13984 checklistsJun 1-7: 0% of 8897 checklistsJun 8-14: 0% of 8504 checklistsJun 15-21: 0% of 8078 checklistsJun 22-30: 0% of 9665 checklistsJul 1-7: 0% of 7144 checklistsJul 8-14: 0% of 6557 checklistsJul 15-21: 0% of 6430 checklistsJul 22-31: 0% of 8696 checklistsAug 1-7: 0% of 5896 checklistsAug 8-14: 0% of 5643 checklistsAug 15-21: 0% of 6151 checklistsAug 22-31: 0% of 7863 checklistsSep 1-7: 0% of 5769 checklistsSep 8-14: 0% of 5646 checklistsSep 15-21: 0% of 5460 checklistsSep 22-30: 0% of 6363 checklistsOct 1-7: 0.1% of 4980 checklistsOct 8-14: 0.1% of 5096 checklistsOct 15-21: 0.2% of 4878 checklistsOct 22-31: 0.8% of 6426 checklistsNov 1-7: 1.3% of 4822 checklistsNov 8-14: 1.7% of 4999 checklistsNov 15-21: 1.6% of 4601 checklistsNov 22-30: 1.4% of 6027 checklistsDec 1-7: 1.7% of 4180 checklistsDec 8-14: 1.1% of 4775 checklistsDec 15-21: 0.8% of 6522 checklistsDec 22-31: 1.2% of 7792 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 Idaho 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.

Embed this map on your site

Where in Idaho

Best counties

Share of checklists at the peak
  1. Custer CountyBest mid February · 12 checklists that week, 3,853 in all40%
  2. Jerome CountyBest mid January · 12 checklists that week, 804 in all19%
  3. Jefferson CountyBest the second week of November · 29 checklists that week, 5,319 in all18%
  4. Bingham CountyBest late January · 11 checklists that week, 1,427 in all15%
  5. Elmore CountyBest late November · 71 checklists that week, 6,239 in all14%
  6. Lemhi CountyBest early February · 83 checklists that week, 6,242 in all13%

Best spots

Share of checklists at the peak
  1. Blacks Creek ReservoirAda County, best late January · 28 checklists that week, 3,935 in all46%
  2. Morley Nelson Snake River Birds of Prey National Conservation AreaElmore County, best late November · 27 checklists that week, 1,056 in all31%
  3. Hubbard ReservoirAda County, best the second week of November · 21 checklists that week, 682 in all18%
  4. Mann LakeNez Perce County, best the second week of November · 47 checklists that week, 1,366 in all15%
  5. Snake River Area of Critical Environmental Concern (Warm Slough)Madison County, best early January · 27 checklists that week, 161 in all13%

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

Best time of day

In Idaho, the American Tree Sparrow is most often listed on checklists started between 9 and 11 am (0.6% of those checklists).

0%0.5%1%12 am: too few checklists (180) to judge1 am: too few checklists (176) to judge2 am: too few checklists (169) to judge3 am: too few checklists (164) to judge4 am: too few checklists (450) to judge5 am: too few checklists (2270) to judge6 am: 0.1% of 9122 checklists7 am: 0.3% of 22204 checklists8 am: 0.5% of 38672 checklists9 am: 0.6% of 38930 checklists10 am: 0.6% of 37338 checklists11 am: 0.6% of 33508 checklists12 pm: 0.5% of 28544 checklists1 pm: 0.6% of 25774 checklists2 pm: 0.6% of 24296 checklists3 pm: 0.6% of 21784 checklists4 pm: 0.4% of 19051 checklists5 pm: 0.2% of 14150 checklists6 pm: 0.1% of 10014 checklists7 pm: 0.1% of 7495 checklists8 pm: too few checklists (4352) to judge9 pm: too few checklists (1449) to judge10 pm: too few checklists (525) to judge11 pm: too few checklists (208) 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
January1.7%1.4%1.7%1.2%
February1.2%1.4%0.9%0.9%
March0.9%1.0%1.0%0.5%
April0.2%0.1%0.1%0.1%
May0%0%0.1%0%
June0%0%0%0%
July0%0%0%0%
August0%0%0%0%
September0%0%0%0%
October0.1%0.1%0.2%0.8%
November1.3%1.7%1.6%1.4%
December1.7%1.1%0.8%1.2%

Neighboring states

  • Montana: arrives early October, 3 weeks earlier than Idaho
  • Utah: arrives early November, 1 week later than Idaho
  • Wyoming: arrives mid October, 1 week earlier than Idaho
  • Colorado: arrives mid October, 1 week earlier than Idaho

Common questions

When do American Tree Sparrows arrive in Idaho?
American Tree Sparrows are winter birds in Idaho: they arrive in late October, peak in the second week of January (1.6% of checklists), and most are gone by mid March.
When do American Tree Sparrows leave Idaho?
Most American Tree Sparrows have left Idaho by mid March, when reports fall below half their usual rate.
When is the best time to see a American Tree Sparrow in Idaho?
The American Tree Sparrow is reported most often in the second week of January, on about 1.6% of Idaho checklists.
Where in Idaho are American Tree Sparrows seen most often?
By county, Custer County, Jerome County, and Jefferson County have the highest peak reporting rates for the American Tree Sparrow (counties with at least 200 checklists).