WhenToBird

Circus hudsonius · Accipitridae

When Do Northern Harriers Arrive in Massachusetts?

Northern Harriers are winter birds in Massachusetts: the first arrive in late July, they are common by mid August, peak in early January (5.6% of checklists), and most are gone by mid April.

When to look

First arrivalsJul 22-31late July
Common byAug 15-21mid August
PeakJan 1-7early January
Most gone byApr 15-21mid April

Best: early January. First arrivals late July; most are gone by mid April. Peak: on about 5.6% of Massachusetts checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marcommon
  4. Aprcommon
  5. Mayuncommon
  6. Junrare
  7. Juluncommon
  8. Augcommon
  9. Seppeak season
  10. Octpeak season
  11. Novpeak season
  12. Decpeak season

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

0%2%4%6%8%Jan 1-7: 4.9% of 43252 checklistsJan 8-14: 5.4% of 30096 checklistsJan 15-21: 5.0% of 28760 checklistsJan 22-31: 5.1% of 38135 checklistsFeb 1-7: 4.7% of 26442 checklistsFeb 8-14: 4.4% of 29034 checklistsFeb 15-21: 3.8% of 37383 checklistsFeb 22-28: 4.2% of 29977 checklistsMar 1-7: 3.7% of 29175 checklistsMar 8-14: 3.6% of 32399 checklistsMar 15-21: 3.3% of 34444 checklistsMar 22-31: 3.2% of 49126 checklistsApr 1-7: 3.5% of 36456 checklistsApr 8-14: 3.5% of 40908 checklistsApr 15-21: 2.8% of 42078 checklistsApr 22-30: 2.4% of 56465 checklistsMay 1-7: 1.9% of 56994 checklistsMay 8-14: 1.3% of 64079 checklistsMay 15-21: 0.8% of 52020 checklistsMay 22-31: 0.6% of 55402 checklistsJun 1-7: 0.5% of 30682 checklistsJun 8-14: 0.5% of 27557 checklistsJun 15-21: 0.5% of 26163 checklistsJun 22-30: 0.5% of 29576 checklistsJul 1-7: 0.7% of 23931 checklistsJul 8-14: 0.7% of 22389 checklistsJul 15-21: 0.7% of 22365 checklistsJul 22-31: 1.0% of 32631 checklistsAug 1-7: 1.6% of 25133 checklistsAug 8-14: 2.1% of 24610 checklistsAug 15-21: 2.6% of 25350 checklistsAug 22-31: 3.2% of 37198 checklistsSep 1-7: 3.6% of 27402 checklistsSep 8-14: 4.4% of 27700 checklistsSep 15-21: 5.0% of 28398 checklistsSep 22-30: 5.0% of 34646 checklistsOct 1-7: 4.9% of 28620 checklistsOct 8-14: 5.4% of 30144 checklistsOct 15-21: 5.0% of 28893 checklistsOct 22-31: 5.1% of 38869 checklistsNov 1-7: 5.3% of 29782 checklistsNov 8-14: 5.5% of 27582 checklistsNov 15-21: 5.2% of 26642 checklistsNov 22-30: 5.2% of 34390 checklistsDec 1-7: 5.0% of 25164 checklistsDec 8-14: 4.8% of 24892 checklistsDec 15-21: 4.9% of 29022 checklistsDec 22-31: 6.3% of 44323 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 Massachusetts 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 Massachusetts

Best counties

Share of checklists at the peak
  1. Nantucket CountyBest the second week of December · 355 checklists that week, 23,895 in all28%
  2. Dukes CountyBest late October · 505 checklists that week, 23,670 in all13%
  3. Essex CountyBest late December · 6238 checklists that week, 213,973 in all12%
  4. Plymouth CountyBest mid January · 1652 checklists that week, 89,282 in all12%
  5. Hampshire CountyBest early January · 3820 checklists that week, 162,423 in all11%
  6. Barnstable CountyBest the second week of November · 3397 checklists that week, 215,188 in all8.4%

Best spots

Share of checklists at the peak
  1. Great Cedar SwampPlymouth County, best mid December · 23 checklists that week, 1,402 in all91%
  2. Madaket Conservation AreaNantucket County, best mid November · 21 checklists that week, 1,071 in all82%
  3. Southwick Wildlife Management AreaHampden County, best late November · 25 checklists that week, 853 in all82%
  4. Hate CoveEssex County, best late January · 197 checklists that week, 8,243 in all77%

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

Best time of day

In Massachusetts, the Northern Harrier is most often listed on checklists started between 1 and 3 pm (3.9% of those checklists).

0%1%2%3%4%12 am: too few checklists (630) to judge1 am: too few checklists (657) to judge2 am: too few checklists (645) to judge3 am: too few checklists (850) to judge4 am: too few checklists (3787) to judge5 am: too few checklists (29743) to judge6 am: 2.9% of 108601 checklists7 am: 3.1% of 186104 checklists8 am: 3.5% of 185905 checklists9 am: 3.8% of 166049 checklists10 am: 3.7% of 150508 checklists11 am: 3.6% of 131024 checklists12 pm: 3.5% of 116804 checklists1 pm: 3.8% of 112055 checklists2 pm: 4.0% of 110246 checklists3 pm: 3.7% of 104376 checklists4 pm: 3.3% of 83736 checklists5 pm: 2.1% of 63723 checklists6 pm: 1.3% of 41435 checklists7 pm: too few checklists (21041) to judge8 pm: too few checklists (5240) to judge9 pm: too few checklists (1722) to judge10 pm: too few checklists (1094) to judge11 pm: too few checklists (704) 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
January4.9%5.4%5.0%5.1%
February4.7%4.4%3.8%4.2%
March3.7%3.6%3.3%3.2%
April3.5%3.5%2.8%2.4%
May1.9%1.3%0.8%0.6%
June0.5%0.5%0.5%0.5%
July0.7%0.7%0.7%1.0%
August1.6%2.1%2.6%3.2%
September3.6%4.4%5.0%5.0%
October4.9%5.4%5.0%5.1%
November5.3%5.5%5.2%5.2%
December5.0%4.8%4.9%6.3%

Neighboring states

  • Rhode Island: arrives the second week of August, 2 weeks later than Massachusetts
  • New Hampshire: arrives the second week of August, 2 weeks later than Massachusetts
  • Connecticut: arrives mid August, 3 weeks later than Massachusetts
  • Vermont: arrives early August, 1 week later than Massachusetts

Common questions

When do Northern Harriers arrive in Massachusetts?
Northern Harriers are winter birds in Massachusetts: the first arrive in late July, they are common by mid August, peak in early January (5.6% of checklists), and most are gone by mid April.
When do Northern Harriers leave Massachusetts?
Most Northern Harriers have left Massachusetts by mid April, when reports fall below half their usual rate. Stragglers are still reported until the second week of May.
When is the best time to see a Northern Harrier in Massachusetts?
The Northern Harrier is reported most often in early January, on about 5.6% of Massachusetts checklists.
Where in Massachusetts are Northern Harriers seen most often?
By county, Nantucket County, Dukes County, and Essex County have the highest peak reporting rates for the Northern Harrier (counties with at least 200 checklists).