WhenToBird

Botaurus exilis · Ardeidae

When Do Least Bitterns Arrive in New Jersey?

Adult Least Bittern
Photo: William J. Deml, CC BY 4.0 via iNaturalist

Least Bitterns arrive in New Jersey in the second week of May, peak in late July (1.1% of checklists), and most are gone by early September.

When to look

First arrivalsMay 8-14the second week of May
Common byMay 8-14the second week of May
PeakJul 22-31late July
Most gone bySep 1-7early September

Best: late July. First arrivals the second week of May; most are gone by early September. Peak: on about 1.1% of New Jersey checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Apruncommon
  5. Maycommon
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Sepuncommon
  10. Octrare
  11. Novnot usually seen
  12. Decnot usually seen

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

0%0.5%1%1.5%Jan 1-7: 0% of 28167 checklistsJan 8-14: 0% of 20583 checklistsJan 15-21: 0% of 19739 checklistsJan 22-31: 0% of 24586 checklistsFeb 1-7: 0% of 17226 checklistsFeb 8-14: 0% of 19567 checklistsFeb 15-21: 0% of 26553 checklistsFeb 22-28: 0% of 19046 checklistsMar 1-7: 0% of 17969 checklistsMar 8-14: 0% of 18976 checklistsMar 15-21: 0.1% of 18581 checklistsMar 22-31: 0% of 27590 checklistsApr 1-7: 0% of 21202 checklistsApr 8-14: 0.1% of 23609 checklistsApr 15-21: 0.1% of 25056 checklistsApr 22-30: 0.1% of 36679 checklistsMay 1-7: 0.3% of 38378 checklistsMay 8-14: 0.4% of 44071 checklistsMay 15-21: 0.4% of 34076 checklistsMay 22-31: 0.6% of 32558 checklistsJun 1-7: 0.8% of 18049 checklistsJun 8-14: 0.7% of 15597 checklistsJun 15-21: 0.7% of 14894 checklistsJun 22-30: 0.5% of 17187 checklistsJul 1-7: 0.9% of 13406 checklistsJul 8-14: 0.9% of 12550 checklistsJul 15-21: 1.1% of 12358 checklistsJul 22-31: 1.2% of 18382 checklistsAug 1-7: 0.9% of 13689 checklistsAug 8-14: 0.7% of 14006 checklistsAug 15-21: 0.6% of 14483 checklistsAug 22-31: 0.3% of 23182 checklistsSep 1-7: 0.3% of 17984 checklistsSep 8-14: 0.4% of 18320 checklistsSep 15-21: 0.2% of 20491 checklistsSep 22-30: 0.1% of 26176 checklistsOct 1-7: 0.1% of 24112 checklistsOct 8-14: 0.1% of 24603 checklistsOct 15-21: 0.1% of 24549 checklistsOct 22-31: 0.1% of 26206 checklistsNov 1-7: 0% of 17469 checklistsNov 8-14: 0.1% of 15102 checklistsNov 15-21: 0% of 14958 checklistsNov 22-30: 0% of 19447 checklistsDec 1-7: 0% of 14017 checklistsDec 8-14: 0% of 14625 checklistsDec 15-21: 0% of 16937 checklistsDec 22-31: 0.1% of 26651 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 New Jersey 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 New Jersey

Best counties

Share of checklists at the peak
  1. Bergen CountyBest late July · 1444 checklists that week, 73,457 in all7.8%
  2. Sussex CountyBest the second week of August · 371 checklists that week, 30,305 in all7.5%
  3. Salem CountyBest mid July · 99 checklists that week, 9,658 in all5.5%
  4. Hudson CountyBest early July · 274 checklists that week, 21,191 in all2.3%
  5. Atlantic CountyBest early June · 556 checklists that week, 28,208 in all1.8%
  6. Warren CountyBest mid June · 355 checklists that week, 20,077 in all1.7%

Best spots

Share of checklists at the peak
  1. Wallkill River National Wildlife RefugeSussex County, best late July · 95 checklists that week, 2,362 in all40%
  2. Richard W de Korte ParkBergen County, best mid July · 216 checklists that week, 10,095 in all27%
  3. Mannington PreserveSalem County, best late July · 21 checklists that week, 622 in all24%
  4. Wright CoveBurlington County, best mid May · 21 checklists that week, 793 in all20%
  5. J A Roebling Memorial ParkMercer County, best mid June · 22 checklists that week, 2,271 in all18%

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

Best time of day

In New Jersey, the Least Bittern is most often listed on checklists started between 6 and 8 am (0.3% of those checklists).

0%0.5%1%12 am: too few checklists (746) to judge1 am: too few checklists (640) to judge2 am: too few checklists (606) to judge3 am: too few checklists (755) to judge4 am: too few checklists (1681) to judge5 am: too few checklists (11258) to judge6 am: 0.5% of 50447 checklists7 am: 0.2% of 118312 checklists8 am: 0.3% of 123273 checklists9 am: 0.2% of 107783 checklists10 am: 0.2% of 97537 checklists11 am: 0.1% of 82427 checklists12 pm: 0.1% of 72581 checklists1 pm: 0.1% of 71478 checklists2 pm: 0.1% of 69994 checklists3 pm: 0.1% of 66822 checklists4 pm: 0.2% of 55950 checklists5 pm: 0.2% of 41360 checklists6 pm: 0.4% of 28122 checklists7 pm: too few checklists (14727) to judge8 pm: too few checklists (4257) to judge9 pm: too few checklists (1273) to judge10 pm: too few checklists (920) to judge11 pm: too few checklists (693) 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%0%0%0%
February0%0%0%0%
March0%0%0.1%0%
April0%0.1%0.1%0.1%
May0.3%0.4%0.4%0.6%
June0.8%0.7%0.7%0.5%
July0.9%0.9%1.1%1.2%
August0.9%0.7%0.6%0.3%
September0.3%0.4%0.2%0.1%
October0.1%0.1%0.1%0.1%
November0%0.1%0%0%
December0%0%0%0.1%

Neighboring states

  • Delaware: arrives the second week of May, in the same week than New Jersey
  • District of Columbia: arrives mid June, 5 weeks later than New Jersey
  • South Carolina: arrives mid April, 3 weeks earlier than New Jersey
  • Florida: arrives late February, 10 weeks earlier than New Jersey

Common questions

When do Least Bitterns arrive in New Jersey?
Least Bitterns arrive in New Jersey in the second week of May, peak in late July (1.1% of checklists), and most are gone by early September.
When do Least Bitterns leave New Jersey?
Most Least Bitterns have left New Jersey by early September, when reports fall below half their usual rate.
When is the best time to see a Least Bittern in New Jersey?
The Least Bittern is reported most often in late July, on about 1.1% of New Jersey checklists.
Where in New Jersey are Least Bitterns seen most often?
By county, Bergen County, Sussex County, and Salem County have the highest peak reporting rates for the Least Bittern (counties with at least 200 checklists).