WhenToBird

Circus hudsonius · Accipitridae

When Do Northern Harriers Arrive in Idaho?

Northern Harriers are in Idaho all year, but most are here in spring: numbers build from early March, peak in early April (14% of checklists), and fall back by early May. In the quietest week (mid July) they are still on about 4.4% of checklists.

When to look

Numbers buildMar 1-7early March
PeakApr 1-7early April
Fall back byMay 1-7early May
FewestJul 15-21mid July

Best: early April. Here all year; numbers build from early March and fall back by early May. Peak: on about 14% of Idaho checklists.

  1. Jancommon
  2. Febcommon
  3. Marpeak season
  4. Aprpeak season
  5. Maycommon
  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%15%Jan 1-7: 9.5% of 9357 checklistsJan 8-14: 8.6% of 6408 checklistsJan 15-21: 8.3% of 6358 checklistsJan 22-31: 7.4% of 8601 checklistsFeb 1-7: 7.6% of 5611 checklistsFeb 8-14: 7.7% of 6090 checklistsFeb 15-21: 6.6% of 7973 checklistsFeb 22-28: 9.2% of 5866 checklistsMar 1-7: 9.9% of 6144 checklistsMar 8-14: 11% of 6456 checklistsMar 15-21: 12% of 6786 checklistsMar 22-31: 13% of 9539 checklistsApr 1-7: 14% of 7202 checklistsApr 8-14: 13% of 7608 checklistsApr 15-21: 13% of 8069 checklistsApr 22-30: 11% of 10973 checklistsMay 1-7: 9.5% of 9481 checklistsMay 8-14: 8.4% of 11318 checklistsMay 15-21: 7.5% of 9141 checklistsMay 22-31: 7.1% of 13984 checklistsJun 1-7: 5.7% of 8897 checklistsJun 8-14: 4.9% of 8504 checklistsJun 15-21: 5.2% of 8078 checklistsJun 22-30: 5.0% of 9665 checklistsJul 1-7: 4.5% of 7144 checklistsJul 8-14: 4.6% of 6557 checklistsJul 15-21: 4.6% of 6430 checklistsJul 22-31: 4.0% of 8696 checklistsAug 1-7: 4.9% of 5896 checklistsAug 8-14: 5.0% of 5643 checklistsAug 15-21: 5.8% of 6151 checklistsAug 22-31: 6.4% of 7863 checklistsSep 1-7: 8.4% of 5769 checklistsSep 8-14: 7.5% of 5646 checklistsSep 15-21: 9.5% of 5460 checklistsSep 22-30: 9.1% of 6363 checklistsOct 1-7: 9.1% of 4980 checklistsOct 8-14: 8.7% of 5096 checklistsOct 15-21: 8.9% of 4878 checklistsOct 22-31: 8.5% of 6426 checklistsNov 1-7: 9.4% of 4822 checklistsNov 8-14: 11% of 4999 checklistsNov 15-21: 8.0% of 4601 checklistsNov 22-30: 8.5% of 6027 checklistsDec 1-7: 7.9% of 4180 checklistsDec 8-14: 8.3% of 4775 checklistsDec 15-21: 7.8% of 6522 checklistsDec 22-31: 9.0% 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.

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Where in Idaho

Best counties

Share of checklists at the peak
  1. Jefferson CountyBest late March · 203 checklists that week, 5,319 in all53%
  2. Elmore CountyBest late November · 71 checklists that week, 6,239 in all53%
  3. Jerome CountyBest early October · 43 checklists that week, 804 in all50%
  4. Owyhee CountyBest late December · 202 checklists that week, 7,837 in all43%
  5. Camas CountyBest early November · 11 checklists that week, 2,112 in all38%
  6. Bear Lake CountyBest early October · 21 checklists that week, 1,581 in all37%

Best spots

Share of checklists at the peak
  1. Market Lake Wildlife Management AreaJefferson County, best late March · 45 checklists that week, 697 in all95%
  2. Morley Nelson Snake River Birds of Prey National Conservation AreaElmore County, best early January · 29 checklists that week, 1,056 in all95%
  3. Indian Creek Reservoir Access SiteAda County, best mid March · 39 checklists that week, 1,086 in all82%
  4. Hubbard ReservoirAda County, best the second week of November · 21 checklists that week, 682 in all75%

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

Best time of day

In Idaho, the Northern Harrier is most often listed on checklists started between 2 and 4 pm (9.5% of those checklists).

0%5%10%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: 5.1% of 9122 checklists7 am: 6.7% of 22204 checklists8 am: 7.3% of 38672 checklists9 am: 8.9% of 38930 checklists10 am: 8.9% of 37338 checklists11 am: 8.8% of 33508 checklists12 pm: 8.8% of 28544 checklists1 pm: 8.9% of 25774 checklists2 pm: 9.3% of 24296 checklists3 pm: 9.7% of 21784 checklists4 pm: 8.5% of 19051 checklists5 pm: 7.8% of 14150 checklists6 pm: 7.8% of 10014 checklists7 pm: 6.2% 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
January9.5%8.6%8.3%7.4%
February7.6%7.7%6.6%9.2%
March9.9%11%12%13%
April14%13%13%11%
May9.5%8.4%7.5%7.1%
June5.7%4.9%5.2%5.0%
July4.5%4.6%4.6%4.0%
August4.9%5.0%5.8%6.4%
September8.4%7.5%9.5%9.1%
October9.1%8.7%8.9%8.5%
November9.4%11%8.0%8.5%
December7.9%8.3%7.8%9.0%

Neighboring states

  • Montana: arrives early April, 4 weeks later than Idaho
  • Utah: arrives the second week of August, 21 weeks later than Idaho
  • Oregon: arrives the second week of September, 23 weeks earlier than Idaho
  • Washington: arrives late July, 19 weeks later than Idaho

Common questions

When do Northern Harriers arrive in Idaho?
Northern Harriers are in Idaho all year, but most are here in spring: numbers build from early March, peak in early April (14% of checklists), and fall back by early May. In the quietest week (mid July) they are still on about 4.4% of checklists.
When do Northern Harriers leave Idaho?
Northern Harriers never fully leave Idaho: numbers fall back below half their usual rate by early May, but some are still reported in every week, about 4.4% of checklists at the low.
When is the best time to see a Northern Harrier in Idaho?
The Northern Harrier is reported most often in early April, on about 14% of Idaho checklists.
Where in Idaho are Northern Harriers seen most often?
By county, Jefferson County, Elmore County, and Jerome County have the highest peak reporting rates for the Northern Harrier (counties with at least 200 checklists).