Hummingbirds are amazing little birds that capture the imagination with their ability to hover in mid-air and fly backwards. Their beautiful, iridescent feathers shimmer in the sunlight as they buzz from flower to flower sipping nectar. Hummingbirds are found throughout the Americas, but only a few species can survive cold winters at higher latitudes and elevations.
Quick answer
Most hummingbird species migrate out of Colorado before winter sets in. However, one species called the Calliope Hummingbird does live in Colorado year round in small numbers. The Calliope Hummingbird is the smallest bird species found in North America and is specially adapted to survive cold temperatures. These tiny birds can slow down their metabolisms and go into torpor to conserve energy on winter nights. They also build up fat reserves for additional insulation. By finding protective roosting spots out of the wind and sticking close to warm water sources that remain unfrozen, some Calliope Hummingbirds manage to tough out the winter in Colorado’s mountains.
Do any hummingbirds live in Colorado year round?
Of the 12 species of hummingbirds found in Colorado, only the Calliope Hummingbird regularly spends the winter in the state. All other hummingbird species that breed in Colorado migrate south to warmer climates in Mexico and Central America before winter sets in.
Here are the hummingbird species known to breed in Colorado and their wintering grounds:
- Calliope Hummingbird – Some remain in Colorado year round
- Broad-tailed Hummingbird – Mexico
- Rufous Hummingbird – Mexico
- Black-chinned Hummingbird – Mexico
- Broad-billed Hummingbird – Mexico
- Violet-crowned Hummingbird – Mexico
- White-eared Hummingbird – Mexico
- Allen’s Hummingbird – Mexico
- Anna’s Hummingbird – Mexico and U.S. Pacific Coast
- Costa’s Hummingbird – Mexico
- Berylline Hummingbird – Mexico
- Lucifer Hummingbird – Mexico
As you can see, the Calliope Hummingbird is the only species tough enough to handle a Colorado winter.
Why do most hummingbirds leave Colorado for winter?
Hummingbirds are tropical and subtropical birds that are highly adapted to living in warm climates. Most hummingbird species cannot survive below-freezing temperatures for extended periods of time. When insects become scarce and flowers stop blooming in late fall, hummingbirds start their long migration south to warmer regions where food and shelter will be available.
Here are some key reasons why most hummingbirds leave Colorado before winter:
- Lack of food – Hummingbirds depend on nectar from flowers and small insects like gnats, aphids, and tree sap suckers. Most of these food sources disappear with freezing temperatures.
- Risk of starvation – Hummingbirds have very fast metabolisms and need to eat frequently. They can starve in a matter of hours if they cannot find enough calories.
- Lack of shelter – Hummingbirds build tiny nests that offer no protection from cold winds, snow, and ice. Few natural shelters and roosting spots are available for them to escape the elements.
- Cold temperature danger – Small hummingbirds lose body heat rapidly. Prolonged exposure to sub-freezing temperatures could be fatal.
To survive cold winters, hummingbirds must fly to warmer areas where flowers bloom year round and small insects remain active even when it is freezing farther north.
How do Calliope Hummingbirds survive Colorado winters?
Calliope Hummingbirds are specially adapted to endure cold temperatures better than any other hummingbird species. Here are some of the key adaptations that allow them to survive winters in Colorado’s high mountains:
- Torpor – Calliopes can reduce their metabolic rate and body temperature and enter a torpid state at night to conserve energy.
- Insulation – They plump up with 25-30% more body fat before winter to create a layer of insulation against the cold.
- Wind barriers – They seek out dense thickets, tree cavities, and other natural shelters to escape freezing winds.
- Sap feeding – In winter they get nutrition by eating tree sap from wells pecked by woodpeckers.
- Heat sources – They stick close to warm spots like hot springs that remain unfrozen in winter.
Calliope Hummingbirds also benefit from artificial feeders stocked with sugar water by people. This stable supplemental food source gives them additional energy to survive cold periods when flower nectar is unavailable.
Torpor
Torpor is an extremely useful adaptation that Calliope and other hummingbird species use to survive cold nights. During torpor, the hummingbird enters a deep sleep and its metabolic rate drops so low that it uses very little energy overnight. Body temperature falls from over 100°F to as low as 48°F. Their heart and breathing rates also slow dramatically. Torpor allows Calliopes to conserve a tremendous amount of energy so they can survive when food is limited in winter.
Fat reserves
Building up extra fat reserves in their chest and abdomen provides Calliope Hummingbirds with additional insulation against cold temperatures. This fat padding allows them to shiver and warm up quickly on cold mornings before leaving their roosts. The fat provides a vital source of energy if food is scarce for a few days during extreme cold snaps.
Sheltered roosts
Roosting in protected microclimates out of the wind and weather is critically important for winter survival. Calliopes often choose south-facing canyons and creek drainages that receive more sun exposure. They tuck into dense thickets of shrubs like Gambel oak and willows, in tree cavities, under overhanging stream banks, and in the low branches of conifers. Selecting just the right roost site to minimize heat loss is key.
Sap feeding
In winter, Calliope Hummingbirds get much of their nutrition by lapping up sap flowing from holes drilled in tree bark by sapsucker woodpeckers. Slurping tasty sap from these sap wells provides calories from sugar and protein. Pine, fir, and aspen trees are favorites for sap feeding.
Heat sources
Certain unfrozen water sources become critical habitat for overwintering Calliope Hummingbirds. Hot spring outlets and seeps provide essential warmth that helps hummingbirds conserve energy. Power plant discharges into streams also create open water with warmer temperatures preferred by Calliopes during cold snaps.
Where do Calliope Hummingbirds live in Colorado during winter?
Calliope Hummingbirds are most likely to survive winter along Colorado’s Front Range and in the western part of the state where temperatures tend to be a little warmer on average. Here are some of their key wintering grounds in Colorado:
- Boulder County
- Jefferson County
- Colorado Springs and El Paso County
- Canon City and Fremont County
- Grand Junction and Mesa County
- Montrose and Delta Counties
- San Miguel County
- La Plata County
Within these counties, Calliopes concentrate along warm river corridors, hot springs, and around feeders in mountain communities. Good winter habitat includes willow thickets along unfrozen sections of streams near Glenwood Springs, Cripple Creek, and Colorado Springs.
How many Calliope Hummingbirds stay in Colorado for winter?
Only a tiny fraction of Colorado’s Calliope Hummingbird population – estimated at less than 1% – attempt to overwinter in the state. Banding records indicate that most of the birds that tough out the winters are adult males. Here are some key figures on Calliope Hummingbirds wintering in Colorado:
- Total population size in summer: Approximately 20,000-30,000
- Estimated number wintering: 100-300
- % of population wintering: Less than 1%
- Sex that primarily overwinters: Adult males
Females and young birds born that past summer almost always migrate out of Colorado by early September. The limited food makes winter survival extremely difficult for smaller and less dominant birds.
What do Calliope Hummingbirds eat in winter in Colorado?
Locating enough food is the biggest challenge Calliope Hummingbirds face when overwintering in Colorado. Here are the main food sources they rely on:
- Tree sap – Provides sugar for energy and protein for nutrients
- Insects – Small gnats, flies, and spiders offer essential protein
- Artificial feeders – Sugar water mimics flower nectar
- Willow catkins – Provides nectar in early spring
Tree sap from sap wells is probably the most important winter food source. Pine, fir, aspen, and even leafless deciduous trees like oaks provide sap. Small insects are gleaned from spider webs and vegetation along warm creeks.
Backyard feeders stocked with sugar water offer a vital supplemental food source. Room temperature sugar water is critical so Calliopes don’t lose body heat from consuming cold liquids.
In early spring, blooming willow catkins provide an important natural nectar source before other flowers come into bloom.
Sap wells
Sap wells drilled by sapsucker woodpeckers are an incredibly valuable food resource exploited by overwintering hummingbirds. The sap oozing from these holes contains sugars that offer quick energy. It also contains amino acids and minerals that provide protein and nutrients.
Calliope Hummingbirds cling to tree trunks and lick sap from multiple holes. The sap runs down branches in some spots, and hummingbirds have been observed sucking up dangling droplets. Pine, fir, aspen, cottonwood and birch trees are frequently tapped for sap.
Backyard feeders
Backyard nectar feeders provide Calliopes with an essential supplement food source, especially during extended cold periods when flower and sap are unavailable. Feeders offer sugar water that mimics flower nectar and provides critical energy. In winter, feeders give the birds enough fuel to periodically warm up and leave their roost. The sugar water also helps them replenish energy reserves lost overnight while torpid.
It is important to clean feeders regularly and change sugar water frequently to prevent fermentation and bacteria growth. Unheated indoor feeders or heated outdoor feeders prevent hummingbirds from expending calories warming up cold nectar.
How do Calliope Hummingbirds behave in winter?
Calliope Hummingbirds exhibit specialized behaviors in winter tailored to survive challenging conditions:
- Enter torpor overnight and remain inactive most of the day
- Highly territorial around sap wells and feeders
- Conserve energy by perching more than hovering
- Seek sunny, protected spots to warm up
- Bathe in snow melt and dried grass for feather maintenance
To conserve their limited energy resources, Calliopes spend up to 18 hours per day in a torpid state on their roosts. They wait for occasional warm sunny days to become active and feed. When awake, they fiercely chase other hummingbirds away from food sources.
With insects scarce, Calliopes spend more time perching than hoovering in the cold air which causes additional heat loss. Puffed up while roosting, they orient to the sun and spread their tail and wing feathers to maximize heat absorption on sunny days.
Bathing is still important so Calliopes splash in snowmelt puddles and preen dry grass seeds into their feathers to clean them and reinforce waterproofing.
Territorial behavior
Calliope Hummingbirds exhibit highly territorial behavior in winter, aggressively chasing away intruders from good feeding spots. Because sap wells and feeders are limited food sources, the dominant bird wants to monopolize the resource and prevent competitors from sharing it.
Male Calliopes are most aggressive and spend more time patrolling and defending the best sap wells. Females visit briefly to feed then move on. Battles sometimes erupt when another male challenges the territory holder for ownership of the sap well.
Torpor and roosting
To conserve energy, Calliope Hummingbirds spend up to 18 hours a day in torpor while roosting on a protected perch. They pick hidden spots out of the wind that provide cover such as a tree cavity, dense willow thicket, or recess under a stream bank or rock overhang.
Their incredibly slow breathing and heart rate allows them to minimize energy use overnight. Periodically waking up just enough to shiver and raise their body temperature prevents them from getting too cold.
How do Calliope Hummingbirds survive migration?
The migration flight south in fall and north in spring poses severe challenges for the tiny Calliope Hummingbird. Here are some key ways they successfully complete their migratory journeys each year:
- Stop to rest and refuel frequently – They tank up on nectar and insects every few hours along the route to replenish energy reserves. Good habitat with flowers is critical.
- Migrate along coastlines – Coastal areas provide more floral resources and stopover habitat.
- Ride wind currents – Migrating along ridgelines, coasts, and other wind patterns gives them an energetic boost.
- Enter torpor overnight – They reduce their metabolism and body temperature to conserve energy on non-travel days.
- Build up fat – Before migrating, they double their body fat to provide extra energy.
- Fly low over water – Crossing open water like the Gulf of Mexico reduces energy spent on climbing.
Timing their migration to coincide with peak flower blooms ensures plentiful nectar supplies along the route. Some people also provide nectar feeders along migration pathways to help sustain these incredible long-distance flyers.
Frequent rest stops
The key to successful migration for Calliope Hummingbirds is making frequent rest stops to refuel. They break up their journey by stopping to tank up on nectar and insects every 3-5 hours. These rest stops allow them to replenish their energy reserves for the next leg of the flight. Good nectar sources along the migration route are essential.
Coastal route
Many Calliopes follow a coastal migration route along California and Mexico which provides more reliable flower resources. Nectar-rich flowers like sages, ocotillos, aloes, and eucalyptus bloom in coastal areas when inland areas are dry. The coast also provides water sources critical for rehydration.
Wind assistance
Timing their migration to ride favorable winds gives Calliope Hummingbirds an energetic advantage. Flying along ridgelines and coastlines allows them to gain lift from wind currents and thermal updrafts which reduces energy expenditures during sustained flight.
Conclusion
While most hummingbird species migrate out of Colorado before winter, the tiny Calliope Hummingbird is specially adapted to tough out cold temperatures and find enough food to survive the winter. Their ability to slow their metabolism into torpor overnight and build up fat reserves gives Calliopes a survival edge. A select few of these hardy birds hunker down along warm creeks and take advantage of sap wells and feeders to meet their energetic needs until spring arrives and flowers bloom again.
