WhenToBird

Gavia immer · Gaviidae

When Do Common Loons Arrive in Delaware?

Adult Common Loon
Photo: Hungry-Sarracenia Photo, CC BY 4.0 via iNaturalist

Common Loons are winter birds in Delaware: the first arrive in the second week of October, they are common by early November, peak in the second week of January (9.8% of checklists), and most are gone by mid April.

When to look

First arrivalsOct 8-14the second week of October
Common byNov 1-7early November
PeakJan 8-14the second week of January
Most gone byApr 15-21mid April

Best: the second week of January. First arrivals the second week of October; most are gone by mid April. Peak: on about 9.8% of Delaware checklists.

  1. Janpeak season
  2. Febpeak season
  3. Marcommon
  4. Aprcommon
  5. Mayuncommon
  6. Junrare
  7. Julrare
  8. Augrare
  9. Seprare
  10. Octuncommon
  11. Novcommon
  12. Decpeak season

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

0%5%10%15%Jan 1-7: 9.4% of 5901 checklistsJan 8-14: 10% of 4091 checklistsJan 15-21: 10% of 3841 checklistsJan 22-31: 9.2% of 5084 checklistsFeb 1-7: 10% of 3705 checklistsFeb 8-14: 7.2% of 3991 checklistsFeb 15-21: 7.2% of 6056 checklistsFeb 22-28: 6.9% of 4036 checklistsMar 1-7: 5.9% of 3822 checklistsMar 8-14: 5.4% of 3873 checklistsMar 15-21: 5.6% of 3856 checklistsMar 22-31: 5.1% of 5702 checklistsApr 1-7: 5.0% of 4104 checklistsApr 8-14: 5.0% of 4456 checklistsApr 15-21: 4.4% of 4871 checklistsApr 22-30: 2.8% of 7249 checklistsMay 1-7: 2.0% of 6806 checklistsMay 8-14: 1.7% of 7229 checklistsMay 15-21: 1.2% of 6466 checklistsMay 22-31: 0.7% of 7437 checklistsJun 1-7: 0.6% of 3596 checklistsJun 8-14: 0.5% of 2847 checklistsJun 15-21: 1.3% of 2901 checklistsJun 22-30: 0.8% of 3644 checklistsJul 1-7: 0.7% of 3142 checklistsJul 8-14: 0.7% of 2767 checklistsJul 15-21: 0.3% of 2882 checklistsJul 22-31: 0.5% of 4175 checklistsAug 1-7: 0.5% of 3482 checklistsAug 8-14: 0.2% of 3477 checklistsAug 15-21: 0.1% of 3386 checklistsAug 22-31: 0.2% of 5028 checklistsSep 1-7: 0.1% of 3631 checklistsSep 8-14: 0.2% of 3507 checklistsSep 15-21: 0.1% of 3404 checklistsSep 22-30: 0.4% of 4252 checklistsOct 1-7: 0.7% of 3563 checklistsOct 8-14: 1.4% of 3440 checklistsOct 15-21: 1.6% of 3282 checklistsOct 22-31: 3.1% of 4025 checklistsNov 1-7: 4.2% of 3030 checklistsNov 8-14: 6.1% of 3141 checklistsNov 15-21: 7.4% of 2858 checklistsNov 22-30: 7.9% of 4104 checklistsDec 1-7: 5.9% of 2472 checklistsDec 8-14: 6.2% of 2415 checklistsDec 15-21: 3.9% of 3306 checklistsDec 22-31: 9.6% of 5527 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 Delaware 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 Delaware

Best counties

Share of checklists at the peak
  1. Sussex CountyBest late January · 2664 checklists that week, 91,027 in all18%
  2. New Castle CountyBest the second week of April · 1835 checklists that week, 72,140 in all2.1%
  3. Kent CountyBest the second week of November · 730 checklists that week, 36,693 in all1.6%

Best spots

Share of checklists at the peak
  1. Mare Marsh (Indian River Inlet)Sussex County, best late January · 29 checklists that week, 247 in all91%
  2. Mare MarshSussex County, best the second week of January · 237 checklists that week, 4,142 in all85%
  3. Delaware Seashore State ParkSussex County, best the second week of April · 39 checklists that week, 1,997 in all65%
  4. Rehoboth MarshSussex County, best early January · 20 checklists that week, 255 in all51%
  5. Cape Henlopen State ParkSussex County, best the second week of April · 52 checklists that week, 3,103 in all50%
  6. Cape Henlopen State Park (southeast)Sussex County, best mid November · 46 checklists that week, 1,352 in all49%

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

Best time of day

In Delaware, the Common Loon is most often listed on checklists started between 9 and 11 am (4.6% of those checklists).

0%2%4%6%12 am: too few checklists (129) to judge1 am: too few checklists (122) to judge2 am: too few checklists (102) to judge3 am: too few checklists (114) to judge4 am: too few checklists (210) to judge5 am: too few checklists (1334) to judge6 am: 3.1% of 8055 checklists7 am: 3.5% of 21367 checklists8 am: 4.3% of 25648 checklists9 am: 4.6% of 22669 checklists10 am: 4.5% of 20679 checklists11 am: 4.5% of 17516 checklists12 pm: 4.3% of 15361 checklists1 pm: 4.4% of 14319 checklists2 pm: 4.3% of 13726 checklists3 pm: 3.5% of 12793 checklists4 pm: 2.4% of 10392 checklists5 pm: 1.5% of 6859 checklists6 pm: 1.1% of 4542 checklists7 pm: too few checklists (2633) to judge8 pm: too few checklists (831) to judge9 pm: too few checklists (211) to judge10 pm: too few checklists (150) to judge11 pm: too few checklists (98) 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
January9.4%10%10%9.2%
February10%7.2%7.2%6.9%
March5.9%5.4%5.6%5.1%
April5.0%5.0%4.4%2.8%
May2.0%1.7%1.2%0.7%
June0.6%0.5%1.3%0.8%
July0.7%0.7%0.3%0.5%
August0.5%0.2%0.1%0.2%
September0.1%0.2%0.1%0.4%
October0.7%1.4%1.6%3.1%
November4.2%6.1%7.4%7.9%
December5.9%6.2%3.9%9.6%

Neighboring states

  • Maryland: arrives mid October, 1 week later than Delaware
  • New Jersey: arrives early October, 1 week earlier than Delaware
  • District of Columbia: arrives mid March, 21 weeks later than Delaware
  • Pennsylvania: arrives mid March, 21 weeks later than Delaware

Common questions

When do Common Loons arrive in Delaware?
Common Loons are winter birds in Delaware: the first arrive in the second week of October, they are common by early November, peak in the second week of January (9.8% of checklists), and most are gone by mid April.
When do Common Loons leave Delaware?
Most Common Loons have left Delaware by mid April, when reports fall below half their usual rate. Stragglers are still reported until mid May.
When is the best time to see a Common Loon in Delaware?
The Common Loon is reported most often in the second week of January, on about 9.8% of Delaware checklists.
Where in Delaware are Common Loons seen most often?
By county, Sussex County, New Castle County, and Kent County have the highest peak reporting rates for the Common Loon (counties with at least 200 checklists).