WhenToBird

Setophaga pensylvanica · Parulidae

When Do Chestnut-sided Warblers Arrive in Maryland?

Adult male Chestnut-sided Warbler
Photo: Matt Felperin, CC BY 4.0 via iNaturalist

Chestnut-sided Warblers reach Maryland in the second week of August, are common by mid August, peak in the second week of September (10% of checklists), and most are gone by early October.

When to look

First arrivalsAug 8-14the second week of August
Common byAug 15-21mid August
PeakSep 8-14the second week of September
Most gone byOct 1-7early October

Best: the second week of September. First arrivals the second week of August; most are gone by early October. Peak: on about 10% of Maryland checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Apruncommon
  5. Maycommon
  6. Jununcommon
  7. Julrare
  8. Augcommon
  9. Seppeak season
  10. Octuncommon
  11. Novnot usually seen
  12. Decnot usually seen

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

0%5%10%15%Jan 1-7: 0.1% of 28716 checklistsJan 8-14: 0% of 21449 checklistsJan 15-21: 0% of 21267 checklistsJan 22-31: 0% of 29144 checklistsFeb 1-7: 0% of 21347 checklistsFeb 8-14: 0% of 22166 checklistsFeb 15-21: 0% of 29986 checklistsFeb 22-28: 0% of 22427 checklistsMar 1-7: 0% of 21389 checklistsMar 8-14: 0% of 22192 checklistsMar 15-21: 0% of 22823 checklistsMar 22-31: 0% of 33720 checklistsApr 1-7: 0% of 25513 checklistsApr 8-14: 0% of 27718 checklistsApr 15-21: 0.1% of 29328 checklistsApr 22-30: 0.8% of 42595 checklistsMay 1-7: 5.4% of 38532 checklistsMay 8-14: 8.0% of 42722 checklistsMay 15-21: 5.6% of 31936 checklistsMay 22-31: 2.5% of 36903 checklistsJun 1-7: 1.6% of 23191 checklistsJun 8-14: 1.5% of 21853 checklistsJun 15-21: 1.6% of 21000 checklistsJun 22-30: 1.2% of 25133 checklistsJul 1-7: 1.2% of 18715 checklistsJul 8-14: 0.6% of 16376 checklistsJul 15-21: 0.6% of 15793 checklistsJul 22-31: 0.4% of 21969 checklistsAug 1-7: 0.4% of 16013 checklistsAug 8-14: 0.7% of 15249 checklistsAug 15-21: 2.4% of 15674 checklistsAug 22-31: 7.3% of 24925 checklistsSep 1-7: 11% of 19808 checklistsSep 8-14: 11% of 18513 checklistsSep 15-21: 8.8% of 21901 checklistsSep 22-30: 5.4% of 22901 checklistsOct 1-7: 2.1% of 19111 checklistsOct 8-14: 0.4% of 18482 checklistsOct 15-21: 0.1% of 17380 checklistsOct 22-31: 0% of 23992 checklistsNov 1-7: 0.1% of 17915 checklistsNov 8-14: 0.1% of 18905 checklistsNov 15-21: 0% of 16259 checklistsNov 22-30: 0% of 22852 checklistsDec 1-7: 0% of 16108 checklistsDec 8-14: 0% of 16512 checklistsDec 15-21: 0% of 18952 checklistsDec 22-31: 0% of 29728 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 Maryland 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 Maryland

Best counties

Share of checklists at the peak
  1. Garrett CountyBest late May · 1675 checklists that week, 37,616 in all31%
  2. Baltimore CountyBest the second week of September · 2367 checklists that week, 136,139 in all19%
  3. Cecil CountyBest the second week of September · 281 checklists that week, 18,620 in all19%
  4. Harford CountyBest the second week of September · 541 checklists that week, 39,311 in all18%
  5. Allegany CountyBest early September · 357 checklists that week, 18,322 in all13%
  6. Montgomery CountyBest the second week of September · 3997 checklists that week, 219,548 in all12%

Best spots

Share of checklists at the peak
  1. Mount Nebo Wildlife Management AreaGarrett County, best late May · 27 checklists that week, 616 in all92%
  2. Finzel Swamp Preserve (Wolf Gap)Allegany County, best late May · 24 checklists that week, 369 in all67%
  3. Pine Lake (Kemp Mill Farms)Montgomery County, best early September · 42 checklists that week, 771 in all65%
  4. Finzel Swamp PreserveGarrett County, best early June · 75 checklists that week, 1,199 in all60%
  5. Sang Run State ParkGarrett County, best early June · 21 checklists that week, 642 in all58%

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

Best time of day

In Maryland, the Chestnut-sided Warbler is most often listed on checklists started between 6 and 8 am (4.0% of those checklists).

0%2%4%6%12 am: too few checklists (486) to judge1 am: too few checklists (451) to judge2 am: too few checklists (447) to judge3 am: too few checklists (766) to judge4 am: too few checklists (2076) to judge5 am: too few checklists (11098) to judge6 am: 4.9% of 56604 checklists7 am: 3.7% of 139255 checklists8 am: 2.3% of 148626 checklists9 am: 1.7% of 126820 checklists10 am: 1.4% of 106973 checklists11 am: 1.1% of 87483 checklists12 pm: 0.9% of 74808 checklists1 pm: 0.9% of 69428 checklists2 pm: 0.9% of 67800 checklists3 pm: 0.8% of 67688 checklists4 pm: 1.0% of 60927 checklists5 pm: 1.2% of 43876 checklists6 pm: 1.2% of 32930 checklists7 pm: too few checklists (19051) to judge8 pm: too few checklists (5708) to judge9 pm: too few checklists (1977) to judge10 pm: too few checklists (1170) to judge11 pm: too few checklists (635) 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
January0.1%0%0%0%
February0%0%0%0%
March0%0%0%0%
April0%0%0.1%0.8%
May5.4%8.0%5.6%2.5%
June1.6%1.5%1.6%1.2%
July1.2%0.6%0.6%0.4%
August0.4%0.7%2.4%7.3%
September11%11%8.8%5.4%
October2.1%0.4%0.1%0%
November0.1%0.1%0%0%
December0%0%0%0%

Neighboring states

  • District of Columbia: arrives the second week of August, in the same week than Maryland
  • Delaware: arrives mid August, 1 week later than Maryland
  • Virginia: arrives late April, 14 weeks earlier than Maryland
  • Pennsylvania: arrives late April, 14 weeks earlier than Maryland

Common questions

When do Chestnut-sided Warblers arrive in Maryland?
Chestnut-sided Warblers reach Maryland in the second week of August, are common by mid August, peak in the second week of September (10% of checklists), and most are gone by early October.
When do Chestnut-sided Warblers leave Maryland?
Most Chestnut-sided Warblers have left Maryland by early October, when reports fall below half their usual rate.
When is the best time to see a Chestnut-sided Warbler in Maryland?
The Chestnut-sided Warbler is reported most often in the second week of September, on about 10% of Maryland checklists.
Where in Maryland are Chestnut-sided Warblers seen most often?
By county, Garrett County, Baltimore County, and Cecil County have the highest peak reporting rates for the Chestnut-sided Warbler (counties with at least 200 checklists).