WhenToBird

6 swallow species in Colorado

When Do Swallows Arrive in Colorado?

Adult Barn Swallow
Photo: Diego González Dopico, CC BY 4.0 via iNaturalist

Barn Swallows, Violet-green Swallows, and Tree Swallows are the swallows you are most likely to see in Colorado. Barn Swallows reach Colorado in the second week of April, are common by mid April, peak in late August (30% of checklists), and most are gone by late September.

When to look

First arrivalsApr 8-14the second week of April
Common byApr 15-21mid April
PeakAug 22-31late August
Most gone bySep 22-30late September

Best: late August. First arrivals the second week of April; most are gone by late September. Peak: on about 30% of Colorado checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprcommon
  5. Maypeak season
  6. Junpeak season
  7. Julpeak season
  8. Augpeak season
  9. Seppeak season
  10. Octuncommon
  11. Novnot usually seen
  12. Decnot usually seen

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

Swallows in Colorado, species by species

SpeciesFirst arrivalsCommon byPeakMost gone byPeak %
Barn SwallowApr 8-14Apr 15-21Aug 22-31Sep 22-3030%
Violet-green SwallowApr 8-14May 1-7Jul 8-14Aug 8-1425%
Tree SwallowMar 22-31Apr 8-14May 8-14Jul 22-3119%
Cliff SwallowApr 15-21May 1-7May 22-31Aug 1-718%
Bank SwallowApr 15-21Apr 15-21May 8-14Sep 1-73.1%
Chimney SwiftApr 22-30Apr 22-30May 15-21Sep 8-141.9%
0%10%20%30%40%Barn SwallowViolet-green SwallowTree SwallowCliff SwallowJanFebMarAprMayJunJulAugSepOctNovDec
  • Barn Swallow
  • Violet-green Swallow
  • Tree Swallow
  • Cliff Swallow
Share of complete checklists reporting each species, by week (4 per month). Gaps: fewer than 10 checklists that week.

Frequency is the share of complete checklists in Colorado 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.

Where in Colorado

Best counties for Barn Swallow

Share of checklists at the peak
  1. Sedgwick CountyBest the second week of August · 12 checklists that week, 1,168 in all81%
  2. Yuma CountyBest the second week of August · 57 checklists that week, 3,844 in all65%
  3. Broomfield CountyBest early August · 234 checklists that week, 16,139 in all65%
  4. Morgan CountyBest the second week of August · 86 checklists that week, 5,181 in all62%
  5. Adams CountyBest mid August · 822 checklists that week, 44,639 in all58%
  6. Washington CountyBest late May · 90 checklists that week, 2,511 in all56%

All swallows in Colorado

6 species are reported regularly: 6 are summer visitors.

#SpeciesPatternThrough the yearFirst arrivalsPeakPeak %
1Barn SwallowSummer visitorApr 8-14Aug 22-3130%
2Violet-green SwallowSummer visitorApr 8-14Jul 8-1425%
3Tree SwallowSummer visitorMar 22-31May 8-1419%
4Cliff SwallowSummer visitorApr 15-21May 22-3118%
5Northern Rough-winged SwallowSummer visitorApr 8-14May 8-1411%
6Bank SwallowSummer visitorApr 15-21May 8-143.1%

Common questions

When do swallows arrive in Colorado?
Barn Swallows reach Colorado in the second week of April, are common by mid April, peak in late August (30% of checklists), and most are gone by late September.
When do swallows leave Colorado?
Most Barn Swallows have left Colorado by late September, when reports fall below half their usual rate. Stragglers are still reported until the second week of October.
When is the best time to see swallows in Colorado?
The Barn Swallow is reported most often in late August, on about 30% of Colorado checklists.
Which swallows are in Colorado?
Barn Swallow, Violet-green Swallow, Tree Swallow, Cliff Swallow, Bank Swallow, and Chimney Swift are reported regularly; the Barn Swallow is the most common.