WhenToBird

Circus hudsonius · Accipitridae

When Do Northern Harriers Arrive in Wyoming?

Northern Harriers are in Wyoming all year, but most are here in spring: numbers build from early April, peak in mid April (9.1% of checklists), and fall back by the second week of May. In the quietest week (the second week of February) they are still on about 2.5% of checklists.

When to look

Numbers buildApr 1-7early April
PeakApr 15-21mid April
Fall back byMay 8-14the second week of May
FewestFeb 8-14the second week of February

Best: mid April. Here all year; numbers build from early April and fall back by the second week of May. Peak: on about 9.1% of Wyoming checklists.

  1. Januncommon
  2. Febuncommon
  3. Marcommon
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Juluncommon
  8. Augcommon
  9. Sepcommon
  10. Octcommon
  11. Novcommon
  12. Deccommon

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

0%5%10%Jan 1-7: 2.9% of 2543 checklistsJan 8-14: 3.7% of 2114 checklistsJan 15-21: 3.2% of 1984 checklistsJan 22-31: 2.8% of 2605 checklistsFeb 1-7: 2.7% of 1940 checklistsFeb 8-14: 2.0% of 1954 checklistsFeb 15-21: 2.6% of 2575 checklistsFeb 22-28: 2.7% of 1932 checklistsMar 1-7: 3.3% of 2486 checklistsMar 8-14: 3.0% of 2535 checklistsMar 15-21: 3.3% of 2726 checklistsMar 22-31: 5.9% of 4349 checklistsApr 1-7: 7.1% of 3300 checklistsApr 8-14: 8.2% of 3500 checklistsApr 15-21: 9.4% of 3701 checklistsApr 22-30: 9.4% of 5887 checklistsMay 1-7: 8.2% of 5341 checklistsMay 8-14: 6.0% of 6910 checklistsMay 15-21: 4.8% of 6884 checklistsMay 22-31: 4.0% of 10652 checklistsJun 1-7: 3.5% of 6807 checklistsJun 8-14: 3.6% of 6714 checklistsJun 15-21: 3.1% of 6708 checklistsJun 22-30: 2.7% of 8160 checklistsJul 1-7: 2.3% of 5755 checklistsJul 8-14: 2.6% of 5379 checklistsJul 15-21: 3.2% of 5299 checklistsJul 22-31: 3.1% of 6830 checklistsAug 1-7: 3.9% of 4581 checklistsAug 8-14: 3.8% of 4625 checklistsAug 15-21: 4.7% of 4466 checklistsAug 22-31: 4.8% of 6562 checklistsSep 1-7: 6.2% of 4543 checklistsSep 8-14: 5.7% of 4652 checklistsSep 15-21: 6.8% of 4186 checklistsSep 22-30: 6.7% of 5301 checklistsOct 1-7: 6.3% of 3248 checklistsOct 8-14: 5.8% of 3010 checklistsOct 15-21: 5.8% of 2624 checklistsOct 22-31: 6.8% of 3170 checklistsNov 1-7: 6.4% of 2110 checklistsNov 8-14: 6.9% of 2153 checklistsNov 15-21: 5.2% of 1971 checklistsNov 22-30: 5.3% of 2136 checklistsDec 1-7: 3.4% of 1646 checklistsDec 8-14: 4.4% of 1609 checklistsDec 15-21: 4.4% of 1954 checklistsDec 22-31: 3.1% 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. Sublette CountyBest late April · 230 checklists that week, 6,738 in all30%
  2. Goshen CountyBest early April · 27 checklists that week, 1,920 in all20%
  3. Weston CountyBest the second week of November · 15 checklists that week, 2,297 in all19%
  4. Carbon CountyBest the second week of November · 42 checklists that week, 6,429 in all18%
  5. Sweetwater CountyBest early April · 115 checklists that week, 5,064 in all16%
  6. Niobrara CountyBest late September · 11 checklists that week, 423 in all14%

Best spots

Share of checklists at the peak
  1. Hutton Lake National Wildlife RefugeAlbany County, best late April · 56 checklists that week, 936 in all82%
  2. National Elk RefugeTeton County, best late April · 65 checklists that week, 1,797 in all39%
  3. Saratoga LakeCarbon County, best mid April · 21 checklists that week, 626 in all35%
  4. State Lands 1111116182Natrona County, best mid August · 34 checklists that week, 483 in all34%
  5. Meeboer LakeAlbany County, best mid April · 30 checklists that week, 300 in all33%

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

Best time of day

In Wyoming, the Northern Harrier is most often listed on checklists started between 2 and 4 pm (5.2% of those checklists).

0%2%4%6%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: 4.4% of 8808 checklists7 am: 5.1% of 18458 checklists8 am: 5.1% of 22143 checklists9 am: 5.1% of 21499 checklists10 am: 4.9% of 19425 checklists11 am: 4.3% of 16017 checklists12 pm: 4.0% of 13868 checklists1 pm: 4.4% of 12984 checklists2 pm: 5.4% of 12605 checklists3 pm: 5.0% of 11821 checklists4 pm: 5.1% of 10571 checklists5 pm: 4.8% of 8746 checklists6 pm: 4.5% of 6707 checklists7 pm: 3.2% 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
January2.9%3.7%3.2%2.8%
February2.7%2.0%2.6%2.7%
March3.3%3.0%3.3%5.9%
April7.1%8.2%9.4%9.4%
May8.2%6.0%4.8%4.0%
June3.5%3.6%3.1%2.7%
July2.3%2.6%3.2%3.1%
August3.9%3.8%4.7%4.8%
September6.2%5.7%6.8%6.7%
October6.3%5.8%5.8%6.8%
November6.4%6.9%5.2%5.3%
December3.4%4.4%4.4%3.1%

Neighboring states

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

Common questions

When do Northern Harriers arrive in Wyoming?
Northern Harriers are in Wyoming all year, but most are here in spring: numbers build from early April, peak in mid April (9.1% of checklists), and fall back by the second week of May. In the quietest week (the second week of February) they are still on about 2.5% of checklists.
When do Northern Harriers leave Wyoming?
Northern Harriers never fully leave Wyoming: numbers fall back below half their usual rate by the second week of May, but some are still reported in every week, about 2.5% of checklists at the low.
When is the best time to see a Northern Harrier in Wyoming?
The Northern Harrier is reported most often in mid April, on about 9.1% of Wyoming checklists.
Where in Wyoming are Northern Harriers seen most often?
By county, Sublette County, Goshen County, and Weston County have the highest peak reporting rates for the Northern Harrier (counties with at least 200 checklists).