WhenToBird

Setophaga virens · Parulidae

When Do Black-throated Green Warblers Arrive in Connecticut?

Adult Black-throated Green Warbler
Photo: Ken Clark, CC BY 4.0 via iNaturalist

Black-throated Green Warblers reach Connecticut in mid April, are common by late April, peak in the second week of May (11% of checklists), and most are gone by the second week of July.

When to look

First arrivalsApr 15-21mid April
Common byApr 22-30late April
PeakMay 8-14the second week of May
Most gone byJul 8-14the second week of July

Best: the second week of May. First arrivals mid April; most are gone by the second week of July. Peak: on about 11% of Connecticut checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprcommon
  5. Maypeak season
  6. Jununcommon
  7. Juluncommon
  8. Auguncommon
  9. Sepcommon
  10. Octcommon
  11. Novnot usually seen
  12. Decnot usually seen

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

0%5%10%15%Jan 1-7: 0% of 18950 checklistsJan 8-14: 0% of 13676 checklistsJan 15-21: 0% of 13377 checklistsJan 22-31: 0% of 17004 checklistsFeb 1-7: 0% of 10218 checklistsFeb 8-14: 0% of 11568 checklistsFeb 15-21: 0% of 15916 checklistsFeb 22-28: 0% of 11413 checklistsMar 1-7: 0% of 10754 checklistsMar 8-14: 0% of 12051 checklistsMar 15-21: 0% of 12616 checklistsMar 22-31: 0.1% of 17801 checklistsApr 1-7: 0% of 13186 checklistsApr 8-14: 0% of 14428 checklistsApr 15-21: 0.1% of 14738 checklistsApr 22-30: 2.4% of 21753 checklistsMay 1-7: 10% of 22494 checklistsMay 8-14: 12% of 23363 checklistsMay 15-21: 10% of 20219 checklistsMay 22-31: 4.1% of 20778 checklistsJun 1-7: 3.1% of 12234 checklistsJun 8-14: 2.7% of 12491 checklistsJun 15-21: 3.0% of 10856 checklistsJun 22-30: 3.2% of 11964 checklistsJul 1-7: 2.2% of 9437 checklistsJul 8-14: 2.2% of 8599 checklistsJul 15-21: 1.7% of 8252 checklistsJul 22-31: 0.9% of 11329 checklistsAug 1-7: 0.4% of 8116 checklistsAug 8-14: 0.5% of 8051 checklistsAug 15-21: 0.8% of 8502 checklistsAug 22-31: 2.4% of 13673 checklistsSep 1-7: 3.8% of 9873 checklistsSep 8-14: 6.1% of 9735 checklistsSep 15-21: 7.5% of 10120 checklistsSep 22-30: 7.5% of 12543 checklistsOct 1-7: 4.4% of 10735 checklistsOct 8-14: 2.3% of 10869 checklistsOct 15-21: 0.6% of 10436 checklistsOct 22-31: 0.2% of 13808 checklistsNov 1-7: 0.1% of 10507 checklistsNov 8-14: 0.1% of 9827 checklistsNov 15-21: 0.1% of 9904 checklistsNov 22-30: 0.1% of 13396 checklistsDec 1-7: 0% of 8974 checklistsDec 8-14: 0% of 9468 checklistsDec 15-21: 0% of 11614 checklistsDec 22-31: 0% of 16616 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 Connecticut 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 Connecticut

Best counties

Share of checklists at the peak
  1. Litchfield CountyBest mid September · 1052 checklists that week, 69,766 in all18%
  2. New Haven CountyBest the second week of May · 5629 checklists that week, 139,721 in all13%
  3. Fairfield CountyBest the second week of May · 4844 checklists that week, 139,848 in all12%
  4. Windham CountyBest the second week of May · 930 checklists that week, 19,034 in all10%
  5. Hartford CountyBest the second week of May · 4171 checklists that week, 105,735 in all9.9%
  6. Middlesex CountyBest the second week of May · 1592 checklists that week, 39,919 in all8.6%

Best spots

Share of checklists at the peak
  1. Yale ForestWindham County, best the second week of May · 43 checklists that week, 327 in all84%
  2. Devils Hopyard State ParkMiddlesex County, best mid May · 20 checklists that week, 172 in all58%
  3. Bluff PointNew London County, best mid September · 109 checklists that week, 770 in all56%
  4. Mclean Game RefugeHartford County, best late May · 21 checklists that week, 353 in all46%
  5. Penwood State ParkHartford County, best the second week of May · 26 checklists that week, 192 in all44%

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

Best time of day

In Connecticut, the Black-throated Green Warbler is most often listed on checklists started between 6 and 8 am (5.1% of those checklists).

0%2%4%6%8%12 am: too few checklists (325) to judge1 am: too few checklists (367) to judge2 am: too few checklists (488) to judge3 am: too few checklists (792) to judge4 am: too few checklists (2722) to judge5 am: too few checklists (9489) to judge6 am: 6.6% of 33657 checklists7 am: 4.4% of 62964 checklists8 am: 3.1% of 70645 checklists9 am: 2.3% of 64870 checklists10 am: 1.8% of 58827 checklists11 am: 1.5% of 51689 checklists12 pm: 1.5% of 45288 checklists1 pm: 1.3% of 44765 checklists2 pm: 1.2% of 44173 checklists3 pm: 1.3% of 41979 checklists4 pm: 1.7% of 33219 checklists5 pm: 2.0% of 24828 checklists6 pm: 1.5% of 15856 checklists7 pm: too few checklists (8126) to judge8 pm: too few checklists (1994) to judge9 pm: too few checklists (533) to judge10 pm: too few checklists (349) to judge11 pm: too few checklists (286) 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%0.1%
April0%0%0.1%2.4%
May10%12%10%4.1%
June3.1%2.7%3.0%3.2%
July2.2%2.2%1.7%0.9%
August0.4%0.5%0.8%2.4%
September3.8%6.1%7.5%7.5%
October4.4%2.3%0.6%0.2%
November0.1%0.1%0.1%0.1%
December0%0%0%0%

Neighboring states

  • Rhode Island: arrives late April, 1 week later than Connecticut
  • Massachusetts: arrives late April, 1 week later than Connecticut
  • New Jersey: arrives mid April, in the same week than Connecticut
  • New York: arrives mid April, in the same week than Connecticut

Common questions

When do Black-throated Green Warblers arrive in Connecticut?
Black-throated Green Warblers reach Connecticut in mid April, are common by late April, peak in the second week of May (11% of checklists), and most are gone by the second week of July.
When do Black-throated Green Warblers leave Connecticut?
Most Black-throated Green Warblers have left Connecticut by the second week of July, when reports fall below half their usual rate. Stragglers are still reported until late July.
When is the best time to see a Black-throated Green Warbler in Connecticut?
The Black-throated Green Warbler is reported most often in the second week of May, on about 11% of Connecticut checklists.
Where in Connecticut are Black-throated Green Warblers seen most often?
By county, Litchfield County, New Haven County, and Fairfield County have the highest peak reporting rates for the Black-throated Green Warbler (counties with at least 200 checklists).