Timing derived from eBird data, 2016–2025 (sourced July 2026)

Colorado doesn't run one hummingbird season — it runs several, stacked by elevation. The Western Slope wakes up in mid-April while high mountain valleys are still under snow, and by the time Broad-taileds are nesting at 9,000 feet, Rufous Hummingbirds are already turning around and heading south again. Nothing here follows a simple north-to-south calendar; altitude sets the clock.

The short answer: put feeders up by mid-to-late April on the Front Range and Western Slope, wait until May at higher mountain elevations, and expect most birds gone by September — though exactly when depends heavily on where in the state you are.

For feeder setup, native plants, and the full species lineup, see our guide to attracting hummingbirds in Colorado.

Colorado's Hummingbird Season at a Glance

Before we get into month-by-month detail, here's the whole season in one picture — four species, four very different curves, all shaped by the same thing: elevation.

How often each species turns up on eBird checklists, week by week — statewide, 2016–2025. The county-by-county elevation breakdown below shows how these same curves shift earlier or later depending on where in Colorado you are.

April: The Western Slope Wakes Up First

Mesa County sees Broad-taileds reliably by mid-April; the Front Range waits until mid-May.

Get feeders up on the Western Slope and in southwestern canyon country by mid-April. If you're on the Front Range or in the foothills, you can wait a couple more weeks — but don't wait too long, since early scouts do show up before the main wave arrives.

May: The Wave Reaches the Mountains — and the Front Range

High-elevation Summit County and metro Denver see Broad-taileds arrive at almost the same time.

This is the month that breaks the "higher elevation means later arrival" assumption. Broad-tailed Hummingbirds are mountain-meadow specialists whose arrival tracks snowmelt and early wildflower bloom rather than elevation itself, so high mountain valleys like Summit County often see reliable activity around the same time as, or even slightly ahead of, the Front Range. If you're above 8,000 feet, have your feeder ready as soon as the snow starts retreating.

June: Nesting Season Begins

Broad-tailed females are on the nest across the state by now.

Feeder activity may quiet slightly as nesting females become less conspicuous, though males continue defending territory and feeding actively.

This is also when Rivoli's Hummingbird, a genuine Colorado rarity, is most likely to be reported — mostly in the mountains or southern part of the state.

Late June–July: Rufous Hummingbirds Are Already Heading South

By late June, Rufous adults are turning around from breeding grounds as far north as Alaska.

This is one of the more surprising things about Colorado's hummingbird calendar: for Rufous Hummingbirds, Colorado's mountain wildflower meadows are already a stop on the return trip south, not the outbound leg. Expect them at feeders and scarlet gilia patches through the mountains starting in July.

August: Peak Migration Traffic

Rufous and Calliope both move through in numbers this month.

This is typically the busiest month at a Colorado feeder, with resident Broad-taileds, southbound Rufous, and the smaller, less predictable Calliope Hummingbird all potentially present at once.

September: Most Birds Depart

Broad-taileds are typically gone by now; Rufous and Calliope finish passing through.

By the end of September, most of Colorado's hummingbirds — resident and migrant alike — have moved on. Scarlet gilia blooming as late as mid-September in high mountain meadows gives the last young birds fuel right before their first migration south.

October: The Last Stragglers

Occasional late Broad-taileds and Rufous may still turn up, especially at lower elevations.

If you keep a feeder up into October, take it down about two weeks after your last sighting — a full October without activity is a safe sign the season is over.

The Year at a Glance, by Elevation

Frequently Asked Questions

When do hummingbirds arrive in Colorado?

Mid-to-late April on the Front Range and Western Slope, and into May at higher mountain elevations. Western Slope counties like Mesa tend to see the earliest arrivals of any part of the state.

When do hummingbirds leave Colorado?

Most Broad-taileds have departed by September. Rufous and Calliope, which pass through as migrants rather than local breeders, are typically gone by late September as well, with occasional stragglers into October.

Why do high mountain areas get hummingbirds so early?

Because Broad-tailed Hummingbirds are mountain-meadow breeding specialists whose arrival tracks snowmelt and early wildflower bloom, not elevation itself. High mountain valleys are the destination, not a late stop along the way — which is why places like Summit County can see birds as early as the Front Range.

Is it bad to leave my feeder up into fall?

No — it's a myth that a feeder left up delays migration. Hummingbirds migrate on daylight and instinct, not food availability. A feeder up into October just gives late migrants a reliable stop.

When is the best time to see hummingbirds in Colorado's mountains?

Late June through August is the richest window in high-elevation meadows, when nesting Broad-taileds overlap with southbound Rufous and Calliope moving through.

How We Built This Calendar

We pulled our own eBird checklist data (2016–2025) for Colorado statewide and for five counties spanning the state's elevation range — Mesa, Montezuma, Summit, Denver, and Yuma — and read the seasonal pattern directly off the reporting rates ourselves. Percentages describe how often a species appears on birdwatchers' submitted checklists, not a population count.

Sources

• eBird bar chart data, Cornell Lab of Ornithology — Colorado statewide and county-level, 2016–2025. Source for all monthly timing and the elevation-arrival pattern.
• All About Birds, Broad-tailed Hummingbird (Cornell Lab of Ornithology). Source for breeding elevation and montane-specialist framing.
• 73rd Report of the Colorado Bird Records Committee (Colorado Field Ornithologists). Source for Rivoli's Hummingbird's accepted Colorado status.
• des Lauriers, J. R. (1994). Hummingbirds eating ashes. The Auk, 111(3), 755–756. Source for the calcium/wood-ash note.