Calliope hummingbirds (Selasphorus calliope) are the smallest breeding bird in North America and one of the smallest birds in the world, weighing only around 3 grams on average. These tiny hummingbirds breed primarily in the mountainous regions of western North America, particularly along the Pacific Coast and Rocky Mountains.
Breeding Range
The breeding range of the calliope hummingbird extends from southern British Columbia in Canada south through Washington, Oregon, California, Idaho, western Montana, Wyoming, Colorado, Utah, and into Arizona and New Mexico. They are found breeding in mountain meadows, pine forests, and river canyons at elevations between 3000-10000 feet. Their range closely overlaps with other small North American hummingbirds like the rufous hummingbird and broad-tailed hummingbird.
Key Breeding Areas
Some of the key breeding areas for calliope hummingbirds include:
- The Cascade Mountains of Washington and Oregon
- The Sierra Nevada Mountains of California
- The Rocky Mountains of Idaho, Montana, and Wyoming
- The Colorado Plateau region spanning parts of Colorado, Utah, and New Mexico
Within these mountain ranges, calliopes often breed near streams, meadows filled with wildflowers, and in forest openings that provide access to nectar-producing flowers.
Ideal Breeding Habitat
Calliope hummingbirds prefer high elevation mountain habitat for breeding. Their ideal breeding grounds provide:
- Flowers: An abundance of nectar-producing wildflowers such as Indian paintbrush, columbine, bee balm, and fireweed.
- Water: Clean mountain streams and seeps for drinking and bathing.
- Insects: A good supply of small insects including flies, gnats, aphids, and spiders to provide protein.
- Shelter: Scattered trees, shrubs, and rocky outcrops that provide cover from predators and storms.
- Nest Sites: Low branches and scrubby vegetation for anchoring their tiny nests.
Alpine and subalpine meadows that border forests and tree-lined creeks offer the combination of flowers, insects, water, shelter, and nesting materials that calliope hummingbirds seek.
Timing of Breeding Season
Calliope hummingbirds breed between late spring and summer across their montane breeding grounds. The timing of the breeding season varies slightly across their range:
- Pacific Northwest: mid-May through August
- California: mid-May through July
- Rocky Mountains: late May through August
- Southwest: mid-June through mid-August
Breeding gets underway once mountain snowpack has melted enough to open up flower-filled breeding habitat. The availability of insects also helps trigger the start of breeding activities.
Why Summer Breeding?
There are several reasons why calliope hummingbirds breed during the summer months:
- Abundant flowers and insects to feed on during summer
- Snow-free areas opened up at higher elevations
- Long daylight hours for foraging
- Warm weather to minimize energy needed for warmth
All of these factors allow calliopes to take advantage of a short summer window where food and nesting conditions are optimal in alpine areas before cold weather returns.
Courtship and Mating
Once they reach their high elevation breeding grounds in spring, male calliope hummingbirds compete aggressively for breeding territories with reliable nectar supplies. Males perform elaborate courtship displays to attract females, including aerial dive displays and shuttle displays where they fly back and forth in fast horizontal arcs.
If a female is interested, she will perch nearby and cock her tail up to signal receptivity. The two birds may also preen each other’s feathers as a pair bonding activity before copulating. The female must rely solely on stored calories to produce eggs, since she does not feed during the 2 weeks of incubation.
Polygyny
Calliope hummingbirds are polygynous, meaning males mate with multiple females. Males provide no parental care and abandon females after mating. Each male may mate with up to six different females over the course of a breeding season.
Extra-pair Copulations
Females may also engage in “extra-pair copulations” with neighboring males. Even once paired with a male, studies show female calliopes routinely mate with additional males outside of their pair bond. This may help ensure their brood’s genetic diversity.
Nest Building
Female calliope hummingbirds are solely responsible for selecting nest sites, gathering materials, and constructing the nests in which they will lay their eggs. Nests are typically built:
- On downward sloping branches of conifers and aspens
- 1-15 feet off the ground
- In sites sheltered from rain like under hanging branches
Nests are tiny, measuring just 1-2 inches across. They are crafted out of soft plant down, spider webs, and lichens bound together with sticky saliva produced by the female.
Time to Build
It takes 4-7 days for a female to fully construct a new nest, not including time taken to find materials. Old nests are not reused from previous years.
Nest Defense
Females aggressively defend nests from threats and have been known to dive bomb animals as large as bears that get too close. They may also add debris like moss to help camouflage the nest from predators.
Egg Laying and Incubation
Once nest building is complete, the female begins laying her eggs. Key facts about calliope hummingbird eggs and incubation:
- Clutch size: Usually 2 eggs per clutch
- Egg size: About the size of a coffee bean
- Incubation period: 15-17 days
- Number of broods: 1-2 per breeding season
- Incubation: Done solely by the female
The tiny eggs are whitish in color. During incubation, the female sits tight on the nest with her tail and bill protruding upward. She leaves the nest unattended for only very brief periods to drink and bathe.
Double Brooding
Calliope hummingbirds are capable of raising multiple broods in a single breeding season. If conditions allow with adequate food, the female may lay a second clutch around a month after her first fledglings leave the nest from her initial clutch.
Raising Hatchlings
Calliope hummingbird hatchlings emerge from their eggs after 15-17 days of incubation. For their first week of life, the nestlings are essentially immobile, relying on their mother for warmth, shelter, and food.
The female makes hundreds of trips per day to collect food for the chicks. As they grow older, the nestlings gradually gain the strength to perch up and beg for food as their mother approaches.
Growth Rate
Calliope hummingbird chicks grow incredibly quickly. Some key development milestones include:
Age | Developmental Milestones |
---|---|
1 week | Eyes open, sparse downy feathers |
2 weeks | Pinfeathers emerge along feather tracts |
3 weeks | Flight feathers fully emerged |
At 20-25 days old, the nestlings are fully flighted and ready to fledge from the nest.
Fledging
The female continues caring for the fledglings for around 2 weeks after they make their first flight from the nest. She feeds them as they improve flying, hovering, and finding flowers on their own. The young are sexually mature and begin breeding the following year after their first migration south.
Threats and Conservation
Calliope hummingbirds face a variety of threats across their breeding habitats:
- Habitat loss from human development
- Natural events like fires and pine beetle outbreaks
- Competition for nectar from non-native flowers
- Collision hazards from human structures
- Climate change disrupting flowers and nesting
However, calliope populations are actually increasing across much of their range. Providing artificial feeders with sugar water may help supplement their diet and offset some habitat issues.
Conservation Status
The calliope hummingbird has a conservation status of “Least Concern” on the IUCN Red List of Threatened Species. Their widespread distribution provides resiliency against localized habitat disruptions.
Conclusion
In summary, calliope hummingbirds breed primarily in high elevation meadows and forests of the mountains of western North America. Their tiny size allows them to take advantage of short but abundant summer conditions. Females build intricate nests and defend them fiercely. Rapid chick development allows calliopes to fledge multiple broods each summer before migrating back to Mexico for winter.