WhenToBird

Falco columbarius · Falconidae

When Do Merlins Arrive in Delaware?

Adult female Merlin
Photo: Cricket Raspet, CC BY 4.0 via iNaturalist

Merlins arrive in Delaware in early September, peak in late September (4.3% of checklists), and most are gone by the second week of May.

When to look

First arrivalsSep 1-7early September
Common bySep 1-7early September
PeakSep 22-30late September
Most gone byMay 8-14the second week of May

Best: late September. First arrivals early September; most are gone by the second week of May. Peak: on about 4.3% of Delaware checklists.

  1. Januncommon
  2. Febuncommon
  3. Maruncommon
  4. Apruncommon
  5. Mayuncommon
  6. Junnot usually seen
  7. Julnot usually seen
  8. Augrare
  9. Seppeak season
  10. Octpeak season
  11. Novpeak season
  12. Decuncommon

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

0%2%4%6%Jan 1-7: 1.1% of 5901 checklistsJan 8-14: 1.1% of 4091 checklistsJan 15-21: 0.8% of 3841 checklistsJan 22-31: 1.2% of 5084 checklistsFeb 1-7: 1.0% of 3705 checklistsFeb 8-14: 0.8% of 3991 checklistsFeb 15-21: 0.7% of 6056 checklistsFeb 22-28: 0.8% of 4036 checklistsMar 1-7: 0.6% of 3822 checklistsMar 8-14: 0.8% of 3873 checklistsMar 15-21: 0.5% of 3856 checklistsMar 22-31: 1.1% of 5702 checklistsApr 1-7: 1.4% of 4104 checklistsApr 8-14: 1.1% of 4456 checklistsApr 15-21: 1.9% of 4871 checklistsApr 22-30: 1.5% of 7249 checklistsMay 1-7: 1.2% of 6806 checklistsMay 8-14: 0.8% of 7229 checklistsMay 15-21: 0.5% of 6466 checklistsMay 22-31: 0.1% of 7437 checklistsJun 1-7: 0.1% of 3596 checklistsJun 8-14: 0% of 2847 checklistsJun 15-21: 0% of 2901 checklistsJun 22-30: 0% of 3644 checklistsJul 1-7: 0% of 3142 checklistsJul 8-14: 0% of 2767 checklistsJul 15-21: 0% of 2882 checklistsJul 22-31: 0% of 4175 checklistsAug 1-7: 0.1% of 3482 checklistsAug 8-14: 0.1% of 3477 checklistsAug 15-21: 0.1% of 3386 checklistsAug 22-31: 0.3% of 5028 checklistsSep 1-7: 1.3% of 3631 checklistsSep 8-14: 3.4% of 3507 checklistsSep 15-21: 4.6% of 3404 checklistsSep 22-30: 4.4% of 4252 checklistsOct 1-7: 3.9% of 3563 checklistsOct 8-14: 4.6% of 3440 checklistsOct 15-21: 4.2% of 3282 checklistsOct 22-31: 3.8% of 4025 checklistsNov 1-7: 2.9% of 3030 checklistsNov 8-14: 3.0% of 3141 checklistsNov 15-21: 2.4% of 2858 checklistsNov 22-30: 2.3% of 4104 checklistsDec 1-7: 1.1% of 2472 checklistsDec 8-14: 0.9% of 2415 checklistsDec 15-21: 1.3% of 3306 checklistsDec 22-31: 0.9% 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 early October · 1542 checklists that week, 91,027 in all5.9%
  2. Kent CountyBest late September · 734 checklists that week, 36,693 in all4.6%
  3. New Castle CountyBest early November · 1222 checklists that week, 72,140 in all3.5%

Best spots

Share of checklists at the peak
  1. Cape Henlopen State Park (southeast)Sussex County, best early October · 61 checklists that week, 1,352 in all41%
  2. Cape Henlopen State Park (south 2)Sussex County, best mid September · 29 checklists that week, 1,368 in all22%
  3. Cape Henlopen State ParkSussex County, best late April · 57 checklists that week, 3,103 in all16%
  4. Rehoboth FlatsSussex County, best mid September · 48 checklists that week, 2,369 in all13%
  5. Ashland Nature CenterNew Castle County, best the second week of November · 149 checklists that week, 4,658 in all13%

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

Best time of day

In Delaware, the Merlin is most often listed on checklists started between 7 and 9 am (1.7% of those checklists).

0%0.5%1%1.5%2%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: 1.3% of 8055 checklists7 am: 1.6% of 21367 checklists8 am: 1.8% of 25648 checklists9 am: 1.5% of 22669 checklists10 am: 1.1% of 20679 checklists11 am: 1.1% of 17516 checklists12 pm: 1.2% of 15361 checklists1 pm: 1.1% of 14319 checklists2 pm: 1.3% of 13726 checklists3 pm: 1.3% of 12793 checklists4 pm: 1.0% of 10392 checklists5 pm: 1.0% of 6859 checklists6 pm: 0.7% 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
January1.1%1.1%0.8%1.2%
February1.0%0.8%0.7%0.8%
March0.6%0.8%0.5%1.1%
April1.4%1.1%1.9%1.5%
May1.2%0.8%0.5%0.1%
June0.1%0%0%0%
July0%0%0%0%
August0.1%0.1%0.1%0.3%
September1.3%3.4%4.6%4.4%
October3.9%4.6%4.2%3.8%
November2.9%3.0%2.4%2.3%
December1.1%0.9%1.3%0.9%

Neighboring states

  • Maryland: arrives early September, in the same week than Delaware
  • New Jersey: arrives late August, 1 week earlier than Delaware
  • District of Columbia: arrives early September, in the same week than Delaware
  • Pennsylvania: arrives late August, 1 week earlier than Delaware

Common questions

When do Merlins arrive in Delaware?
Merlins arrive in Delaware in early September, peak in late September (4.3% of checklists), and most are gone by the second week of May.
When do Merlins leave Delaware?
Most Merlins have left Delaware by the second week of May, when reports fall below half their usual rate.
When is the best time to see a Merlin in Delaware?
The Merlin is reported most often in late September, on about 4.3% of Delaware checklists.
Where in Delaware are Merlins seen most often?
By county, Sussex County, Kent County, and New Castle County have the highest peak reporting rates for the Merlin (counties with at least 200 checklists).