When do grackles and blackbirds leave Colorado?

Red-winged Blackbirds never fully leave Colorado: numbers fall back below half their usual rate by late June, but some are still reported in every week, about 16% of checklists at the low.

When is the best time to see grackles and blackbirds in Colorado?

The Red-winged Blackbird is reported most often in early May, on about 53% of Colorado checklists.

Which grackles and blackbirds are in Colorado?

Red-winged Blackbird, Common Grackle, Western Meadowlark, Brown-headed Cowbird, Yellow-headed Blackbird, and Bobolink are reported regularly; the Red-winged Blackbird is the most common.

6 blackbird species in Colorado

When Do Grackles and blackbirds Arrive in Colorado?

Photo: infiniteuniverse, CC0 1.0 via iNaturalist

Red-winged Blackbirds, Common Grackles, and Western Meadowlarks are the grackles and blackbirds you are most likely to see in Colorado. Red-winged Blackbirds are in Colorado all year, but most are here in spring: numbers build from early March, peak in early May (53% of checklists), and fall back by late June. In the quietest week (early September) they are still on about 16% of checklists.

When to look

Numbers buildMar 1-7early March

PeakMay 1-7early May

Fall back byJun 22-30late June

FewestSep 1-7early September

Best: early May. Here all year; numbers build from early March and fall back by late June. Peak: on about 53% of Colorado checklists.

Januncommon
Febcommon
Marpeak season
Aprpeak season
Maypeak season
Junpeak season
Julcommon
Augcommon
Sepuncommon
Octcommon
Novcommon
Decuncommon

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

Grackles and blackbirds in Colorado, species by species

Species	First arrivals	Common by	Peak	Most gone by	Peak %
Red-winged Blackbird	Mar 1-7	Mar 1-7	May 1-7	Jun 22-30	53%
Common Grackle	Mar 15-21	Apr 1-7	May 8-14	Jul 15-21	36%
Western Meadowlark	Mar 15-21	Mar 15-21	Apr 22-30	Jun 22-30	30%
Brown-headed Cowbird	Apr 8-14	Apr 22-30	May 15-21	Jul 8-14	25%
Yellow-headed Blackbird	Apr 1-7	Apr 1-7	Apr 22-30	Sep 22-30	7.0%
Bobolink	May 15-21	May 15-21	Jun 1-7	Jul 1-7	1.3%

Red-winged Blackbird
Common Grackle
Western Meadowlark
Brown-headed Cowbird

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 Red-winged Blackbird

Share of checklists at the peak

Broomfield CountyBest the second week of May · 601 checklists that week, 16,139 in all84%
Adams CountyBest the second week of May · 1284 checklists that week, 44,639 in all74%
Washington CountyBest early June · 47 checklists that week, 2,511 in all72%
Morgan CountyBest late May · 143 checklists that week, 5,181 in all67%
Logan CountyBest early May · 102 checklists that week, 4,117 in all67%
Yuma CountyBest mid May · 133 checklists that week, 3,844 in all65%

Common questions

When do grackles and blackbirds arrive in Colorado?: Red-winged Blackbirds are in Colorado all year, but most are here in spring: numbers build from early March, peak in early May (53% of checklists), and fall back by late June. In the quietest week (early September) they are still on about 16% of checklists.
When do grackles and blackbirds leave Colorado?: Red-winged Blackbirds never fully leave Colorado: numbers fall back below half their usual rate by late June, but some are still reported in every week, about 16% of checklists at the low.
When is the best time to see grackles and blackbirds in Colorado?: The Red-winged Blackbird is reported most often in early May, on about 53% of Colorado checklists.
Which grackles and blackbirds are in Colorado?: Red-winged Blackbird, Common Grackle, Western Meadowlark, Brown-headed Cowbird, Yellow-headed Blackbird, and Bobolink are reported regularly; the Red-winged Blackbird is the most common.