WhenToBird

Stelgidopteryx serripennis · Hirundinidae

When Do Northern Rough-winged Swallows Arrive in California?

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

Northern Rough-winged Swallows reach California in the second week of February, are common by early March, peak in late April (13% of checklists), and most are gone by the second week of July.

When to look

First arrivalsFeb 8-14the second week of February
Common byMar 1-7early March
PeakApr 22-30late April
Most gone byJul 8-14the second week of July

Best: late April. First arrivals the second week of February; most are gone by the second week of July. Peak: on about 13% of California checklists.

  1. Jannot usually seen
  2. Febuncommon
  3. Marpeak season
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Sepuncommon
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%5%10%15%Jan 1-7: 0.3% of 112336 checklistsJan 8-14: 0.3% of 85518 checklistsJan 15-21: 0.3% of 86488 checklistsJan 22-31: 0.3% of 116174 checklistsFeb 1-7: 0.7% of 75171 checklistsFeb 8-14: 1.1% of 84467 checklistsFeb 15-21: 1.8% of 105683 checklistsFeb 22-28: 3.8% of 83396 checklistsMar 1-7: 6.2% of 77470 checklistsMar 8-14: 8.1% of 75180 checklistsMar 15-21: 9.2% of 80770 checklistsMar 22-31: 11% of 114116 checklistsApr 1-7: 12% of 84057 checklistsApr 8-14: 13% of 83692 checklistsApr 15-21: 13% of 89242 checklistsApr 22-30: 13% of 114289 checklistsMay 1-7: 14% of 85728 checklistsMay 8-14: 12% of 91984 checklistsMay 15-21: 13% of 75478 checklistsMay 22-31: 12% of 106250 checklistsJun 1-7: 11% of 70051 checklistsJun 8-14: 12% of 67485 checklistsJun 15-21: 12% of 66269 checklistsJun 22-30: 11% of 79172 checklistsJul 1-7: 8.8% of 62877 checklistsJul 8-14: 6.7% of 60328 checklistsJul 15-21: 5.6% of 59705 checklistsJul 22-31: 4.3% of 83796 checklistsAug 1-7: 3.8% of 60215 checklistsAug 8-14: 3.2% of 60172 checklistsAug 15-21: 2.9% of 59877 checklistsAug 22-31: 2.5% of 89107 checklistsSep 1-7: 2.2% of 72000 checklistsSep 8-14: 1.3% of 71228 checklistsSep 15-21: 1.0% of 76808 checklistsSep 22-30: 0.6% of 100204 checklistsOct 1-7: 0.4% of 76571 checklistsOct 8-14: 0.3% of 80874 checklistsOct 15-21: 0.2% of 74581 checklistsOct 22-31: 0.3% of 97498 checklistsNov 1-7: 0.3% of 70851 checklistsNov 8-14: 0.2% of 72431 checklistsNov 15-21: 0.2% of 66767 checklistsNov 22-30: 0.2% of 94737 checklistsDec 1-7: 0.3% of 65393 checklistsDec 8-14: 0.2% of 67449 checklistsDec 15-21: 0.2% of 83421 checklistsDec 22-31: 0.2% of 124993 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 California 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 California

Best counties

Share of checklists at the peak
  1. Imperial CountyBest early April · 455 checklists that week, 24,551 in all26%
  2. Kings CountyBest late May · 99 checklists that week, 3,688 in all26%
  3. Los Angeles CountyBest early June · 6747 checklists that week, 410,235 in all23%
  4. Orange CountyBest the second week of May · 5516 checklists that week, 244,559 in all22%
  5. Ventura CountyBest early May · 2043 checklists that week, 94,391 in all21%
  6. Stanislaus CountyBest the second week of May · 768 checklists that week, 30,240 in all20%

Best spots

Share of checklists at the peak
  1. Salt Pond (historical)Los Angeles County, best late March · 22 checklists that week, 776 in all98%
  2. San Fernando ValleyLos Angeles County, best late April · 21 checklists that week, 1,124 in all96%
  3. Carmel Valley Open SpaceSan Diego County, best late March · 24 checklists that week, 379 in all96%
  4. Guadalupe River ParkSanta Clara County, best mid June · 37 checklists that week, 1,165 in all94%
  5. Hansen Dam Recreation AreaLos Angeles County, best late June · 49 checklists that week, 2,011 in all91%

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

Best time of day

In California, the Northern Rough-winged Swallow is most often listed on checklists started between 6 and 8 am (6.9% of those checklists).

0%2%4%6%8%12 am: too few checklists (1688) to judge1 am: too few checklists (1451) to judge2 am: too few checklists (1402) to judge3 am: too few checklists (1743) to judge4 am: too few checklists (4647) to judge5 am: too few checklists (32158) to judge6 am: 7.4% of 186053 checklists7 am: 6.7% of 444086 checklists8 am: 5.9% of 535846 checklists9 am: 5.0% of 486061 checklists10 am: 4.5% of 411130 checklists11 am: 3.9% of 325798 checklists12 pm: 3.8% of 269132 checklists1 pm: 3.6% of 244762 checklists2 pm: 3.6% of 235420 checklists3 pm: 3.6% of 232365 checklists4 pm: 4.1% of 208688 checklists5 pm: 5.5% of 146104 checklists6 pm: 5.9% of 96867 checklists7 pm: too few checklists (50942) to judge8 pm: too few checklists (14803) to judge9 pm: too few checklists (5561) to judge10 pm: too few checklists (3546) to judge11 pm: too few checklists (2092) 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
January0.3%0.3%0.3%0.3%
February0.7%1.1%1.8%3.8%
March6.2%8.1%9.2%11%
April12%13%13%13%
May14%12%13%12%
June11%12%12%11%
July8.8%6.7%5.6%4.3%
August3.8%3.2%2.9%2.5%
September2.2%1.3%1.0%0.6%
October0.4%0.3%0.2%0.3%
November0.3%0.2%0.2%0.2%
December0.3%0.2%0.2%0.2%

Neighboring states

  • Nevada: arrives the second week of March, 4 weeks later than California
  • Utah: arrives the second week of March, 4 weeks later than California
  • Arizona: arrives mid February, 1 week later than California
  • Oregon: arrives early April, 7 weeks later than California

Common questions

When do Northern Rough-winged Swallows arrive in California?
Northern Rough-winged Swallows reach California in the second week of February, are common by early March, peak in late April (13% of checklists), and most are gone by the second week of July.
When do Northern Rough-winged Swallows leave California?
Most Northern Rough-winged Swallows have left California by the second week of July, when reports fall below half their usual rate. Stragglers are still reported until the second week of September.
When is the best time to see a Northern Rough-winged Swallow in California?
The Northern Rough-winged Swallow is reported most often in late April, on about 13% of California checklists.
Where in California are Northern Rough-winged Swallows seen most often?
By county, Imperial County, Kings County, and Los Angeles County have the highest peak reporting rates for the Northern Rough-winged Swallow (counties with at least 200 checklists).