WhenToBird

Circus hudsonius · Accipitridae

When Do Northern Harriers Arrive in Montana?

Northern Harriers are in Montana all year, but most are here in spring: numbers build from early April, peak in mid April (11% of checklists), and fall back by late May. In the quietest week (early February) they are still on about 2.6% of checklists.

When to look

Numbers buildApr 1-7early April
PeakApr 15-21mid April
Fall back byMay 22-31late May
FewestFeb 1-7early February

Best: mid April. Here all year; numbers build from early April and fall back by late May. Peak: on about 11% of Montana checklists.

  1. Januncommon
  2. Febuncommon
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Julcommon
  8. Augcommon
  9. Seppeak season
  10. Octpeak season
  11. Novcommon
  12. Deccommon

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

0%5%10%15%Jan 1-7: 4.2% of 7987 checklistsJan 8-14: 2.7% of 5561 checklistsJan 15-21: 3.1% of 5613 checklistsJan 22-31: 2.6% of 7881 checklistsFeb 1-7: 2.5% of 5018 checklistsFeb 8-14: 2.7% of 5598 checklistsFeb 15-21: 2.8% of 7247 checklistsFeb 22-28: 2.5% of 5531 checklistsMar 1-7: 3.0% of 6110 checklistsMar 8-14: 3.7% of 6623 checklistsMar 15-21: 4.9% of 7687 checklistsMar 22-31: 6.4% of 11095 checklistsApr 1-7: 7.7% of 7774 checklistsApr 8-14: 10% of 8785 checklistsApr 15-21: 11% of 9684 checklistsApr 22-30: 11% of 13805 checklistsMay 1-7: 10% of 11847 checklistsMay 8-14: 8.9% of 13547 checklistsMay 15-21: 7.9% of 13019 checklistsMay 22-31: 6.7% of 20456 checklistsJun 1-7: 5.8% of 12993 checklistsJun 8-14: 5.0% of 11594 checklistsJun 15-21: 5.2% of 11159 checklistsJun 22-30: 4.7% of 13786 checklistsJul 1-7: 4.5% of 9584 checklistsJul 8-14: 4.3% of 9078 checklistsJul 15-21: 4.2% of 7905 checklistsJul 22-31: 4.9% of 10906 checklistsAug 1-7: 5.3% of 7335 checklistsAug 8-14: 5.8% of 6868 checklistsAug 15-21: 5.3% of 6866 checklistsAug 22-31: 6.6% of 10076 checklistsSep 1-7: 8.1% of 7670 checklistsSep 8-14: 8.6% of 7490 checklistsSep 15-21: 9.3% of 6804 checklistsSep 22-30: 9.3% of 8016 checklistsOct 1-7: 9.1% of 5996 checklistsOct 8-14: 8.0% of 6156 checklistsOct 15-21: 7.6% of 5742 checklistsOct 22-31: 7.4% of 7790 checklistsNov 1-7: 6.3% of 5353 checklistsNov 8-14: 5.7% of 5475 checklistsNov 15-21: 4.1% of 4603 checklistsNov 22-30: 4.9% of 6067 checklistsDec 1-7: 5.0% of 4362 checklistsDec 8-14: 5.5% of 4467 checklistsDec 15-21: 5.2% of 5328 checklistsDec 22-31: 4.5% 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. Deer Lodge CountyBest late April · 328 checklists that week, 8,732 in all40%
  2. Wheatland CountyBest mid July · 40 checklists that week, 1,384 in all35%
  3. Petroleum CountyBest late August · 10 checklists that week, 427 in all35%
  4. Teton CountyBest early September · 87 checklists that week, 2,579 in all34%
  5. Hill CountyBest the second week of April · 12 checklists that week, 988 in all33%
  6. Lake CountyBest late September · 408 checklists that week, 19,478 in all30%

Best spots

Share of checklists at the peak
  1. Lee Metcalf National Wildlife Refuge (northeast)Ravalli County, best the second week of May · 29 checklists that week, 838 in all89%
  2. Warm Springs Wildlife Management AreaDeer Lodge County, best the second week of April · 31 checklists that week, 838 in all76%

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

Best time of day

In Montana, the Northern Harrier is most often listed on checklists started between 10 am and 12 pm (6.8% of those checklists).

0%2%4%6%8%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: 6.2% of 12719 checklists7 am: 5.8% of 31202 checklists8 am: 5.6% of 47646 checklists9 am: 6.7% of 44624 checklists10 am: 7.0% of 40704 checklists11 am: 6.7% of 33825 checklists12 pm: 6.6% of 29407 checklists1 pm: 6.4% of 27959 checklists2 pm: 6.5% of 26928 checklists3 pm: 6.2% of 25313 checklists4 pm: 6.3% of 22151 checklists5 pm: 6.4% of 16884 checklists6 pm: 6.0% of 13780 checklists7 pm: 5.6% 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
January4.2%2.7%3.1%2.6%
February2.5%2.7%2.8%2.5%
March3.0%3.7%4.9%6.4%
April7.7%10%11%11%
May10%8.9%7.9%6.7%
June5.8%5.0%5.2%4.7%
July4.5%4.3%4.2%4.9%
August5.3%5.8%5.3%6.6%
September8.1%8.6%9.3%9.3%
October9.1%8.0%7.6%7.4%
November6.3%5.7%4.1%4.9%
December5.0%5.5%5.2%4.5%

Neighboring states

  • Idaho: arrives early March, 4 weeks earlier than Montana
  • Wyoming: arrives early April, in the same week than Montana
  • Utah: arrives the second week of August, 17 weeks later than Montana
  • Washington: arrives late July, 15 weeks later than Montana

Common questions

When do Northern Harriers arrive in Montana?
Northern Harriers are in Montana all year, but most are here in spring: numbers build from early April, peak in mid April (11% of checklists), and fall back by late May. In the quietest week (early February) they are still on about 2.6% of checklists.
When do Northern Harriers leave Montana?
Northern Harriers never fully leave Montana: numbers fall back below half their usual rate by late May, but some are still reported in every week, about 2.6% of checklists at the low.
When is the best time to see a Northern Harrier in Montana?
The Northern Harrier is reported most often in mid April, on about 11% of Montana checklists.
Where in Montana are Northern Harriers seen most often?
By county, Deer Lodge County, Wheatland County, and Petroleum County have the highest peak reporting rates for the Northern Harrier (counties with at least 200 checklists).