WhenToBird

Ardea herodias · Ardeidae

When Do Great Blue Herons Arrive in Maryland?

Adult Great Blue Heron
Photo: mostbittern, CC BY 4.0 via iNaturalist

The Great Blue Heron is in Maryland all year. It turns up on about 27% of checklists at its peak (the second week of August) and on 13% in its quietest week (the second week of February).

When to look

PresentAll year
Peak weekAug 8-14the second week of August
Quietest weekFeb 8-14the second week of February

Best: the second week of August. Here all year. Peak: on about 27% of Maryland checklists.

  1. Jancommon
  2. Febcommon
  3. Marcommon
  4. Aprcommon
  5. Maycommon
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octpeak season
  11. Novpeak season
  12. Decpeak season

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

0%10%20%30%Jan 1-7: 16% of 28716 checklistsJan 8-14: 15% of 21449 checklistsJan 15-21: 14% of 21267 checklistsJan 22-31: 14% of 29144 checklistsFeb 1-7: 14% of 21347 checklistsFeb 8-14: 13% of 22166 checklistsFeb 15-21: 11% of 29986 checklistsFeb 22-28: 14% of 22427 checklistsMar 1-7: 13% of 21389 checklistsMar 8-14: 14% of 22192 checklistsMar 15-21: 17% of 22823 checklistsMar 22-31: 19% of 33720 checklistsApr 1-7: 19% of 25513 checklistsApr 8-14: 19% of 27718 checklistsApr 15-21: 19% of 29328 checklistsApr 22-30: 19% of 42595 checklistsMay 1-7: 18% of 38532 checklistsMay 8-14: 19% of 42722 checklistsMay 15-21: 19% of 31936 checklistsMay 22-31: 20% of 36903 checklistsJun 1-7: 20% of 23191 checklistsJun 8-14: 18% of 21853 checklistsJun 15-21: 19% of 21000 checklistsJun 22-30: 20% of 25133 checklistsJul 1-7: 22% of 18715 checklistsJul 8-14: 23% of 16376 checklistsJul 15-21: 26% of 15793 checklistsJul 22-31: 27% of 21969 checklistsAug 1-7: 27% of 16013 checklistsAug 8-14: 27% of 15249 checklistsAug 15-21: 28% of 15674 checklistsAug 22-31: 26% of 24925 checklistsSep 1-7: 25% of 19808 checklistsSep 8-14: 24% of 18513 checklistsSep 15-21: 25% of 21901 checklistsSep 22-30: 25% of 22901 checklistsOct 1-7: 24% of 19111 checklistsOct 8-14: 24% of 18482 checklistsOct 15-21: 23% of 17380 checklistsOct 22-31: 22% of 23992 checklistsNov 1-7: 22% of 17915 checklistsNov 8-14: 24% of 18905 checklistsNov 15-21: 22% of 16259 checklistsNov 22-30: 21% of 22852 checklistsDec 1-7: 21% of 16108 checklistsDec 8-14: 19% of 16512 checklistsDec 15-21: 17% of 18952 checklistsDec 22-31: 19% 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. Somerset CountyBest mid November · 57 checklists that week, 9,451 in all47%
  2. Dorchester CountyBest early August · 224 checklists that week, 26,161 in all46%
  3. Talbot CountyBest late July · 630 checklists that week, 31,140 in all43%
  4. Queen Anne's CountyBest early August · 590 checklists that week, 26,875 in all43%
  5. Kent CountyBest late July · 250 checklists that week, 13,396 in all41%
  6. Harford CountyBest early May · 1576 checklists that week, 39,311 in all37%

Best spots

Share of checklists at the peak
  1. Carroll BranchMontgomery County, best the second week of May · 23 checklists that week, 1,769 in all98%
  2. Chesapeake Beach Railway TrailCalvert County, best mid December · 22 checklists that week, 986 in all97%
  3. Blackwater National Wildlife RefugeDorchester County, best the second week of June · 54 checklists that week, 3,907 in all97%
  4. Patuxent River ParkAnne Arundel County, best late July · 22 checklists that week, 1,189 in all97%

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

Best time of day

In Maryland, the Great Blue Heron is most often listed on checklists started between 6 and 8 am (25% of those checklists).

0%10%20%30%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: 30% of 56604 checklists7 am: 24% of 139255 checklists8 am: 21% of 148626 checklists9 am: 20% of 126820 checklists10 am: 19% of 106973 checklists11 am: 18% of 87483 checklists12 pm: 17% of 74808 checklists1 pm: 17% of 69428 checklists2 pm: 18% of 67800 checklists3 pm: 18% of 67688 checklists4 pm: 17% of 60927 checklists5 pm: 18% of 43876 checklists6 pm: 18% 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
January16%15%14%14%
February14%13%11%14%
March13%14%17%19%
April19%19%19%19%
May18%19%19%20%
June20%18%19%20%
July22%23%26%27%
August27%27%28%26%
September25%24%25%25%
October24%24%23%22%
November22%24%22%21%
December21%19%17%19%

Neighboring states

Common questions

When do Great Blue Herons arrive in Maryland?
The Great Blue Heron is in Maryland all year. It turns up on about 27% of checklists at its peak (the second week of August) and on 13% in its quietest week (the second week of February).
When do Great Blue Herons leave Maryland?
The Great Blue Heron does not leave Maryland: it is reported all year, from 13% of checklists in the second week of February to 27% in the second week of August.
When is the best time to see a Great Blue Heron in Maryland?
The Great Blue Heron is reported most often in the second week of August, on about 27% of Maryland checklists.
Where in Maryland are Great Blue Herons seen most often?
By county, Somerset County, Dorchester County, and Talbot County have the highest peak reporting rates for the Great Blue Heron (counties with at least 200 checklists).