WhenToBird

Toxostoma rufum · Mimidae

When Do Brown Thrashers Arrive in Montana?

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

Brown Thrashers arrive in Montana in the second week of May, peak in late May (2.4% of checklists), and most are gone by late July.

When to look

First arrivalsMay 8-14the second week of May
Common byMay 8-14the second week of May
PeakMay 22-31late May
Most gone byJul 22-31late July

Best: late May. First arrivals the second week of May; most are gone by late July. Peak: on about 2.4% of Montana checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprnot usually seen
  5. Maypeak season
  6. Junpeak season
  7. Juluncommon
  8. Augcommon
  9. Sepcommon
  10. Octrare
  11. Novnot usually seen
  12. Decnot usually seen

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

0%1%2%3%4%Jan 1-7: 0.1% of 7987 checklistsJan 8-14: 0.1% of 5561 checklistsJan 15-21: 0.1% of 5613 checklistsJan 22-31: 0.1% of 7881 checklistsFeb 1-7: 0.1% of 5018 checklistsFeb 8-14: 0% of 5598 checklistsFeb 15-21: 0.1% of 7247 checklistsFeb 22-28: 0% of 5531 checklistsMar 1-7: 0.1% of 6110 checklistsMar 8-14: 0% of 6623 checklistsMar 15-21: 0% of 7687 checklistsMar 22-31: 0% of 11095 checklistsApr 1-7: 0% of 7774 checklistsApr 8-14: 0% of 8785 checklistsApr 15-21: 0% of 9684 checklistsApr 22-30: 0.1% of 13805 checklistsMay 1-7: 0.2% of 11847 checklistsMay 8-14: 1.1% of 13547 checklistsMay 15-21: 2.2% of 13019 checklistsMay 22-31: 3.0% of 20456 checklistsJun 1-7: 1.8% of 12993 checklistsJun 8-14: 1.9% of 11594 checklistsJun 15-21: 1.1% of 11159 checklistsJun 22-30: 1.0% of 13786 checklistsJul 1-7: 0.7% of 9584 checklistsJul 8-14: 0.6% of 9078 checklistsJul 15-21: 0.7% of 7905 checklistsJul 22-31: 0.6% of 10906 checklistsAug 1-7: 0.6% of 7335 checklistsAug 8-14: 0.4% of 6868 checklistsAug 15-21: 0.9% of 6866 checklistsAug 22-31: 1.2% of 10076 checklistsSep 1-7: 2.2% of 7670 checklistsSep 8-14: 2.2% of 7490 checklistsSep 15-21: 0.8% of 6804 checklistsSep 22-30: 0.2% of 8016 checklistsOct 1-7: 0.2% of 5996 checklistsOct 8-14: 0.1% of 6156 checklistsOct 15-21: 0.1% of 5742 checklistsOct 22-31: 0% of 7790 checklistsNov 1-7: 0% of 5353 checklistsNov 8-14: 0% of 5475 checklistsNov 15-21: 0% of 4603 checklistsNov 22-30: 0% of 6067 checklistsDec 1-7: 0% of 4362 checklistsDec 8-14: 0% of 4467 checklistsDec 15-21: 0% of 5328 checklistsDec 22-31: 0% of 6672 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 Montana 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 Montana

Best counties

Share of checklists at the peak
  1. Valley CountyBest early September · 115 checklists that week, 3,392 in all36%
  2. Sheridan CountyBest the second week of September · 108 checklists that week, 2,316 in all27%
  3. Wibaux CountyBest mid May · 31 checklists that week, 435 in all26%
  4. Custer CountyBest late May · 107 checklists that week, 1,404 in all25%
  5. McCone CountyBest early September · 12 checklists that week, 537 in all22%
  6. Musselshell CountyBest late July · 24 checklists that week, 961 in all20%

Best spots

Share of checklists at the peak
  1. Downstream Recreation AreaValley County, best early June · 45 checklists that week, 487 in all72%
  2. American Prairie FoundationPhillips County, best mid May · 35 checklists that week, 287 in all54%
  3. Onstad Park (Westby)Sheridan County, best late May · 45 checklists that week, 123 in all45%
  4. Spoted Eagle Recreation AreaCuster County, best late May · 34 checklists that week, 347 in all42%
  5. Boxelder Lake (Plentywood)Sheridan County, best late May · 53 checklists that week, 119 in all36%
  6. Starter PondPhillips County, best late May · 63 checklists that week, 227 in all33%

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

Best time of day

In Montana, the Brown Thrasher is most often listed on checklists started between 6 and 8 am (1.5% of those checklists).

0%1%2%3%12 am: too few checklists (183) to judge1 am: too few checklists (169) to judge2 am: too few checklists (163) to judge3 am: too few checklists (212) to judge4 am: too few checklists (503) to judge5 am: too few checklists (4022) to judge6 am: 2.4% of 12719 checklists7 am: 1.1% of 31202 checklists8 am: 0.7% of 47646 checklists9 am: 0.5% of 44624 checklists10 am: 0.5% of 40704 checklists11 am: 0.5% of 33825 checklists12 pm: 0.4% of 29407 checklists1 pm: 0.5% of 27959 checklists2 pm: 0.4% of 26928 checklists3 pm: 0.5% of 25313 checklists4 pm: 0.6% of 22151 checklists5 pm: 0.8% of 16884 checklists6 pm: 0.8% of 13780 checklists7 pm: 0.9% of 9926 checklists8 pm: too few checklists (5765) to judge9 pm: too few checklists (2099) to judge10 pm: too few checklists (595) to judge11 pm: too few checklists (230) 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%
March0.1%0%0%0%
April0%0%0%0.1%
May0.2%1.1%2.2%3.0%
June1.8%1.9%1.1%1.0%
July0.7%0.6%0.7%0.6%
August0.6%0.4%0.9%1.2%
September2.2%2.2%0.8%0.2%
October0.2%0.1%0.1%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Wyoming: arrives late April, 2 weeks earlier than Montana
  • Colorado: arrives late April, 2 weeks earlier than Montana
  • North Dakota: arrives late April, 2 weeks earlier than Montana
  • South Dakota: arrives mid April, 3 weeks earlier than Montana

Common questions

When do Brown Thrashers arrive in Montana?
Brown Thrashers arrive in Montana in the second week of May, peak in late May (2.4% of checklists), and most are gone by late July.
When do Brown Thrashers leave Montana?
Most Brown Thrashers have left Montana by late July, when reports fall below half their usual rate.
When is the best time to see a Brown Thrasher in Montana?
The Brown Thrasher is reported most often in late May, on about 2.4% of Montana checklists.
Where in Montana are Brown Thrashers seen most often?
By county, Valley County, Sheridan County, and Wibaux County have the highest peak reporting rates for the Brown Thrasher (counties with at least 200 checklists).