WhenToBird

Tachycineta bicolor · Hirundinidae

When Do Tree Swallows Arrive in California?

Adult Tree Swallow
Photo: Carter Dorscht, CC0 1.0 via iNaturalist

Tree Swallows reach California in mid January, are common by mid February, peak in late April (17% of checklists), and most are gone by mid July.

When to look

First arrivalsJan 15-21mid January
Common byFeb 15-21mid February
PeakApr 22-30late April
Most gone byJul 15-21mid July

Best: late April. First arrivals mid January; most are gone by mid July. Peak: on about 17% of California checklists.

  1. Januncommon
  2. Febcommon
  3. Marpeak season
  4. Aprpeak season
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Sepuncommon
  10. Octrare
  11. Novrare
  12. Decrare

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

0%5%10%15%20%Jan 1-7: 2.6% of 112336 checklistsJan 8-14: 2.7% of 85518 checklistsJan 15-21: 3.2% of 86488 checklistsJan 22-31: 4.5% of 116174 checklistsFeb 1-7: 6.1% of 75171 checklistsFeb 8-14: 7.4% of 84467 checklistsFeb 15-21: 8.0% of 105683 checklistsFeb 22-28: 10% of 83396 checklistsMar 1-7: 12% of 77470 checklistsMar 8-14: 14% of 75180 checklistsMar 15-21: 14% of 80770 checklistsMar 22-31: 15% of 114116 checklistsApr 1-7: 16% of 84057 checklistsApr 8-14: 17% of 83692 checklistsApr 15-21: 17% of 89242 checklistsApr 22-30: 17% of 114289 checklistsMay 1-7: 17% of 85728 checklistsMay 8-14: 17% of 91984 checklistsMay 15-21: 17% of 75478 checklistsMay 22-31: 16% of 106250 checklistsJun 1-7: 16% of 70051 checklistsJun 8-14: 15% of 67485 checklistsJun 15-21: 14% of 66269 checklistsJun 22-30: 13% of 79172 checklistsJul 1-7: 12% of 62877 checklistsJul 8-14: 9.5% of 60328 checklistsJul 15-21: 8.7% of 59705 checklistsJul 22-31: 7.0% of 83796 checklistsAug 1-7: 5.0% of 60215 checklistsAug 8-14: 4.1% of 60172 checklistsAug 15-21: 3.4% of 59877 checklistsAug 22-31: 3.0% of 89107 checklistsSep 1-7: 2.7% of 72000 checklistsSep 8-14: 2.4% of 71228 checklistsSep 15-21: 2.2% of 76808 checklistsSep 22-30: 1.9% of 100204 checklistsOct 1-7: 1.8% of 76571 checklistsOct 8-14: 2.1% of 80874 checklistsOct 15-21: 1.9% of 74581 checklistsOct 22-31: 1.9% of 97498 checklistsNov 1-7: 1.9% of 70851 checklistsNov 8-14: 1.8% of 72431 checklistsNov 15-21: 1.6% of 66767 checklistsNov 22-30: 1.8% of 94737 checklistsDec 1-7: 1.8% of 65393 checklistsDec 8-14: 1.7% of 67449 checklistsDec 15-21: 1.9% of 83421 checklistsDec 22-31: 2.0% 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. Lake CountyBest mid April · 287 checklists that week, 12,989 in all55%
  2. Yolo CountyBest early July · 760 checklists that week, 67,424 in all50%
  3. Sutter CountyBest mid May · 93 checklists that week, 4,996 in all48%
  4. Glenn CountyBest mid March · 52 checklists that week, 5,189 in all42%
  5. Sacramento CountyBest early May · 2627 checklists that week, 121,767 in all42%
  6. Plumas CountyBest late April · 899 checklists that week, 24,629 in all40%

Best spots

Share of checklists at the peak
  1. Sacramento Regional County Sanitation DistrictSacramento County, best the second week of April · 46 checklists that week, 2,065 in all100%
  2. American River ParkwaySacramento County, best mid April · 32 checklists that week, 1,855 in all100%
  3. Sacramento Regional County Sanitation District (southeast)Sacramento County, best late April · 22 checklists that week, 247 in all100%
  4. Riverbottom ParkFresno County, best late April · 28 checklists that week, 508 in all99%
  5. Mather Regional ParkSacramento County, best the second week of May · 55 checklists that week, 1,173 in all98%
  6. South Fork PreserveYolo County, best the second week of May · 28 checklists that week, 935 in all98%

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

Best time of day

In California, the Tree Swallow is most often listed on checklists started between 7 and 9 am (9.7% of those checklists).

0%5%10%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: 9.8% of 186053 checklists7 am: 9.6% of 444086 checklists8 am: 9.8% of 535846 checklists9 am: 9.0% of 486061 checklists10 am: 8.2% of 411130 checklists11 am: 7.3% of 325798 checklists12 pm: 6.6% of 269132 checklists1 pm: 6.4% of 244762 checklists2 pm: 6.0% of 235420 checklists3 pm: 5.7% of 232365 checklists4 pm: 5.8% of 208688 checklists5 pm: 6.9% of 146104 checklists6 pm: 7.7% 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
January2.6%2.7%3.2%4.5%
February6.1%7.4%8.0%10%
March12%14%14%15%
April16%17%17%17%
May17%17%17%16%
June16%15%14%13%
July12%9.5%8.7%7.0%
August5.0%4.1%3.4%3.0%
September2.7%2.4%2.2%1.9%
October1.8%2.1%1.9%1.9%
November1.9%1.8%1.6%1.8%
December1.8%1.7%1.9%2.0%

Neighboring states

  • Nevada: arrives mid January, in the same week than California
  • Utah: arrives the second week of March, 7 weeks later than California
  • Arizona: arrives mid January, in the same week than California
  • Oregon: arrives mid February, 4 weeks later than California

Common questions

When do Tree Swallows arrive in California?
Tree Swallows reach California in mid January, are common by mid February, peak in late April (17% of checklists), and most are gone by mid July.
When do Tree Swallows leave California?
Most Tree Swallows have left California by mid July, when reports fall below half their usual rate. Stragglers are still reported until late August.
When is the best time to see a Tree Swallow in California?
The Tree Swallow is reported most often in late April, on about 17% of California checklists.
Where in California are Tree Swallows seen most often?
By county, Lake County, Yolo County, and Sutter County have the highest peak reporting rates for the Tree Swallow (counties with at least 200 checklists).