WhenToBird

Stelgidopteryx serripennis · Hirundinidae

When Do Northern Rough-winged Swallows Arrive in Wyoming?

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

Northern Rough-winged Swallows reach Wyoming in mid April, are common by late April, peak in mid May (8.6% of checklists), and most are gone by mid August.

When to look

First arrivalsApr 15-21mid April
Common byApr 22-30late April
PeakMay 15-21mid May
Most gone byAug 15-21mid August

Best: mid May. First arrivals mid April; most are gone by mid August. Peak: on about 8.6% of Wyoming checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Apruncommon
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Augcommon
  9. Seprare
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%5%10%Jan 1-7: 0% of 2543 checklistsJan 8-14: 0% of 2114 checklistsJan 15-21: 0% of 1984 checklistsJan 22-31: 0% of 2605 checklistsFeb 1-7: 0% of 1940 checklistsFeb 8-14: 0% of 1954 checklistsFeb 15-21: 0% of 2575 checklistsFeb 22-28: 0% of 1932 checklistsMar 1-7: 0% of 2486 checklistsMar 8-14: 0% of 2535 checklistsMar 15-21: 0% of 2726 checklistsMar 22-31: 0% of 4349 checklistsApr 1-7: 0% of 3300 checklistsApr 8-14: 0.1% of 3500 checklistsApr 15-21: 0.4% of 3701 checklistsApr 22-30: 2.7% of 5887 checklistsMay 1-7: 5.9% of 5341 checklistsMay 8-14: 8.1% of 6910 checklistsMay 15-21: 9.2% of 6884 checklistsMay 22-31: 8.5% of 10652 checklistsJun 1-7: 6.9% of 6807 checklistsJun 8-14: 5.7% of 6714 checklistsJun 15-21: 4.9% of 6708 checklistsJun 22-30: 4.0% of 8160 checklistsJul 1-7: 3.9% of 5755 checklistsJul 8-14: 4.1% of 5379 checklistsJul 15-21: 4.5% of 5299 checklistsJul 22-31: 4.4% of 6830 checklistsAug 1-7: 3.6% of 4581 checklistsAug 8-14: 3.6% of 4625 checklistsAug 15-21: 2.7% of 4466 checklistsAug 22-31: 2.2% of 6562 checklistsSep 1-7: 0.7% of 4543 checklistsSep 8-14: 0.5% of 4652 checklistsSep 15-21: 0.1% of 4186 checklistsSep 22-30: 0.1% of 5301 checklistsOct 1-7: 0% of 3248 checklistsOct 8-14: 0% of 3010 checklistsOct 15-21: 0% of 2624 checklistsOct 22-31: 0% of 3170 checklistsNov 1-7: 0% of 2110 checklistsNov 8-14: 0% of 2153 checklistsNov 15-21: 0% of 1971 checklistsNov 22-30: 0% of 2136 checklistsDec 1-7: 0% of 1646 checklistsDec 8-14: 0% of 1609 checklistsDec 15-21: 0% of 1954 checklistsDec 22-31: 0% of 2392 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 Wyoming 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 Wyoming

Best counties

Share of checklists at the peak
  1. Hot Springs CountyBest early July · 31 checklists that week, 1,345 in all30%
  2. Laramie CountyBest late May · 709 checklists that week, 15,593 in all21%
  3. Uinta CountyBest mid June · 85 checklists that week, 1,881 in all16%
  4. Platte CountyBest mid May · 83 checklists that week, 1,645 in all15%
  5. Lincoln CountyBest mid May · 93 checklists that week, 3,169 in all13%
  6. Goshen CountyBest mid May · 156 checklists that week, 1,920 in all12%

Best spots

Share of checklists at the peak
  1. South Park Wildlife Habitat Management AreaTeton County, best mid May · 78 checklists that week, 756 in all55%
  2. L A K ReservoirWeston County, best late May · 33 checklists that week, 531 in all48%
  3. Wyoming Hereford Ranch Reservoir Number OneLaramie County, best late June · 31 checklists that week, 1,242 in all48%
  4. Usbr (southeast)Lincoln County, best late May · 21 checklists that week, 115 in all45%
  5. French CreekJohnson County, best late May · 21 checklists that week, 397 in all39%

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

Best time of day

In Wyoming, the Northern Rough-winged Swallow is most often listed on checklists started between 6 and 8 pm (3.9% of those checklists).

0%2%4%6%12 am: too few checklists (59) to judge1 am: too few checklists (76) to judge2 am: too few checklists (86) to judge3 am: too few checklists (79) to judge4 am: too few checklists (326) to judge5 am: too few checklists (2271) to judge6 am: 3.9% of 8808 checklists7 am: 3.4% of 18458 checklists8 am: 3.2% of 22143 checklists9 am: 3.0% of 21499 checklists10 am: 2.7% of 19425 checklists11 am: 2.5% of 16017 checklists12 pm: 2.6% of 13868 checklists1 pm: 2.5% of 12984 checklists2 pm: 2.5% of 12605 checklists3 pm: 2.4% of 11821 checklists4 pm: 2.6% of 10571 checklists5 pm: 3.5% of 8746 checklists6 pm: 4.1% of 6707 checklists7 pm: 3.7% of 4890 checklists8 pm: too few checklists (2323) to judge9 pm: too few checklists (554) to judge10 pm: too few checklists (134) to judge11 pm: too few checklists (59) 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%0%
April0%0.1%0.4%2.7%
May5.9%8.1%9.2%8.5%
June6.9%5.7%4.9%4.0%
July3.9%4.1%4.5%4.4%
August3.6%3.6%2.7%2.2%
September0.7%0.5%0.1%0.1%
October0%0%0%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Colorado: arrives the second week of April, 1 week earlier than Wyoming
  • Utah: arrives the second week of March, 5 weeks earlier than Wyoming
  • Montana: arrives the second week of April, 1 week earlier than Wyoming
  • Idaho: arrives late March, 3 weeks earlier than Wyoming

Common questions

When do Northern Rough-winged Swallows arrive in Wyoming?
Northern Rough-winged Swallows reach Wyoming in mid April, are common by late April, peak in mid May (8.6% of checklists), and most are gone by mid August.
When do Northern Rough-winged Swallows leave Wyoming?
Most Northern Rough-winged Swallows have left Wyoming by mid August, when reports fall below half their usual rate. Stragglers are still reported until early September.
When is the best time to see a Northern Rough-winged Swallow in Wyoming?
The Northern Rough-winged Swallow is reported most often in mid May, on about 8.6% of Wyoming checklists.
Where in Wyoming are Northern Rough-winged Swallows seen most often?
By county, Hot Springs County, Laramie County, and Uinta County have the highest peak reporting rates for the Northern Rough-winged Swallow (counties with at least 200 checklists).