WhenToBird

Stelgidopteryx serripennis · Hirundinidae

When Do Northern Rough-winged Swallows Arrive in Delaware?

Adult Northern Rough-winged Swallow
Photo: Peter Chen 2.0, CC BY 4.0 via iNaturalist

Northern Rough-winged Swallows reach Delaware in late March, are common by early April, peak in late April (6.6% of checklists), and most are gone by early August.

When to look

First arrivalsMar 22-31late March
Common byApr 1-7early April
PeakApr 22-30late April
Most gone byAug 1-7early August

Best: late April. First arrivals late March; most are gone by early August. Peak: on about 6.6% of Delaware checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Maruncommon
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Julcommon
  8. Auguncommon
  9. Seprare
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%2%4%6%8%Jan 1-7: 0% of 5901 checklistsJan 8-14: 0% of 4091 checklistsJan 15-21: 0% of 3841 checklistsJan 22-31: 0% of 5084 checklistsFeb 1-7: 0% of 3705 checklistsFeb 8-14: 0% of 3991 checklistsFeb 15-21: 0% of 6056 checklistsFeb 22-28: 0% of 4036 checklistsMar 1-7: 0% of 3822 checklistsMar 8-14: 0% of 3873 checklistsMar 15-21: 0.1% of 3856 checklistsMar 22-31: 0.9% of 5702 checklistsApr 1-7: 3.3% of 4104 checklistsApr 8-14: 4.3% of 4456 checklistsApr 15-21: 6.3% of 4871 checklistsApr 22-30: 7.0% of 7249 checklistsMay 1-7: 6.6% of 6806 checklistsMay 8-14: 6.1% of 7229 checklistsMay 15-21: 4.3% of 6466 checklistsMay 22-31: 4.0% of 7437 checklistsJun 1-7: 4.0% of 3596 checklistsJun 8-14: 3.7% of 2847 checklistsJun 15-21: 4.0% of 2901 checklistsJun 22-30: 4.7% of 3644 checklistsJul 1-7: 2.3% of 3142 checklistsJul 8-14: 3.0% of 2767 checklistsJul 15-21: 2.4% of 2882 checklistsJul 22-31: 2.3% of 4175 checklistsAug 1-7: 1.8% of 3482 checklistsAug 8-14: 1.9% of 3477 checklistsAug 15-21: 1.4% of 3386 checklistsAug 22-31: 1.1% of 5028 checklistsSep 1-7: 0.4% of 3631 checklistsSep 8-14: 0.1% of 3507 checklistsSep 15-21: 0.1% of 3404 checklistsSep 22-30: 0.1% of 4252 checklistsOct 1-7: 0.1% of 3563 checklistsOct 8-14: 0.1% of 3440 checklistsOct 15-21: 0% of 3282 checklistsOct 22-31: 0% of 4025 checklistsNov 1-7: 0% of 3030 checklistsNov 8-14: 0.1% of 3141 checklistsNov 15-21: 0.1% of 2858 checklistsNov 22-30: 0% of 4104 checklistsDec 1-7: 0% of 2472 checklistsDec 8-14: 0% of 2415 checklistsDec 15-21: 0% of 3306 checklistsDec 22-31: 0% 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.

Embed this map on your site

Where in Delaware

Best counties

Share of checklists at the peak
  1. New Castle CountyBest early May · 3005 checklists that week, 72,140 in all14%
  2. Kent CountyBest mid July · 735 checklists that week, 36,693 in all3.4%
  3. Sussex CountyBest mid June · 1377 checklists that week, 91,027 in all1.7%

Best spots

Share of checklists at the peak
  1. Auburn HeightsNew Castle County, best early May · 34 checklists that week, 678 in all78%
  2. Alapocas Run State ParkNew Castle County, best early May · 32 checklists that week, 463 in all68%
  3. White Clay Creek State Park (Lamborn Run)New Castle County, best mid April · 40 checklists that week, 444 in all67%
  4. Brandywine ParkNew Castle County, best early May · 22 checklists that week, 533 in all55%
  5. White Clay Creek State Park (northwest)New Castle County, best the second week of May · 30 checklists that week, 364 in all49%

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

Best time of day

In Delaware, the Northern Rough-winged Swallow is most often listed on checklists started between 5 and 7 pm (2.9% of those checklists).

0%1%2%3%4%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: 2.3% of 8055 checklists7 am: 3.1% of 21367 checklists8 am: 2.2% of 25648 checklists9 am: 2.1% of 22669 checklists10 am: 2.0% of 20679 checklists11 am: 1.2% of 17516 checklists12 pm: 1.2% of 15361 checklists1 pm: 1.2% of 14319 checklists2 pm: 1.0% of 13726 checklists3 pm: 1.4% of 12793 checklists4 pm: 1.5% of 10392 checklists5 pm: 2.5% of 6859 checklists6 pm: 3.5% 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
January0%0%0%0%
February0%0%0%0%
March0%0%0.1%0.9%
April3.3%4.3%6.3%7.0%
May6.6%6.1%4.3%4.0%
June4.0%3.7%4.0%4.7%
July2.3%3.0%2.4%2.3%
August1.8%1.9%1.4%1.1%
September0.4%0.1%0.1%0.1%
October0.1%0.1%0%0%
November0%0.1%0.1%0%
December0%0%0%0%

Neighboring states

Common questions

When do Northern Rough-winged Swallows arrive in Delaware?
Northern Rough-winged Swallows reach Delaware in late March, are common by early April, peak in late April (6.6% of checklists), and most are gone by early August.
When do Northern Rough-winged Swallows leave Delaware?
Most Northern Rough-winged Swallows have left Delaware by early August, when reports fall below half their usual rate. Stragglers are still reported until mid August.
When is the best time to see a Northern Rough-winged Swallow in Delaware?
The Northern Rough-winged Swallow is reported most often in late April, on about 6.6% of Delaware checklists.
Where in Delaware are Northern Rough-winged Swallows seen most often?
By county, New Castle County, Kent County, and Sussex County have the highest peak reporting rates for the Northern Rough-winged Swallow (counties with at least 200 checklists).