Anna’s hummingbirds (Calypte anna) are small, iridescent green and pink birds found along the west coast of North America. They are known for their speedy flight and territorial behavior. Anna’s hummingbirds breed and mate during a fairly defined period each year.
Breeding Season
The breeding season for Anna’s hummingbirds generally runs from November through May, with most mating and nesting activities occurring between December and April. The specific timing can vary slightly based on location and climate conditions each year.
In southern areas like California and Arizona, breeding gets underway in late November or December. Further north along the Pacific Coast into Oregon and Washington, breeding typically starts a bit later in January or February as winter lingers longer.
By early spring, Anna’s hummingbird breeding activity is in full swing throughout their range. The males establish breeding territories and perform elaborate courtship displays to attract females. Once a male woos a female, mating occurs. The female then builds a small cup-shaped nest out of plant down, spider webs and lichens camouflaged with bits of bark where she incubates the eggs.
Nest building and incubation lasts from March through early May in most areas. The young fledge a few weeks after hatching, usually by late May or early June. Some late nests may occur through July.
By mid to late summer, the breeding season winds down. The last fledglings leave the nest and reach independence. The adult male’s courtship displays and aggressive territorial behavior subside as their hormone levels drop after the breeding period ends.
Why Anna’s Hummingbirds Mate in the Winter and Spring
There are several key reasons why Anna’s hummingbirds time their breeding season to occur during the winter and early spring months each year:
- Abundant flower nectar – Winter and early spring is when many flowering plants native to the Pacific Coast bloom, providing a vital source of nectar.
- Insect availability – More insects are active in mild winter and spring weather, giving the small birds a protein source.
- Nesting materials – Plant down is plentiful for nest construction as other plants flower.
- Weather conditions – Winters are relatively mild in their range, allowing successful mating, nesting and raising young.
- Long days for feeding – Long daylight hours in spring and summer allow more time for the high-metabolism birds to feed.
- Lack of competition – Few other hummingbird species breed at the same time.
By timing reproduction to coincide with these advantageous conditions, Anna’s hummingbirds improve their chances of successful mating and raising young.
Courtship Displays
In order to mate, male Anna’s hummingbirds must first attract a female by performing a dazzling courtship display. These displays occur primarily during late fall and winter, though some may continue into early spring.
The showy display consists of a complex series of dives and swoops over the breeding territory. The male flies as high as 100 feet into the air before diving down at high speeds, often making a loud chirping sound as wind rushes through his tail feathers.
At the bottom of the dive, the male abruptly pulls up and soars back upwards while flashing the bright iridescent red-pink throat patch and crown feathers that give the birds their name. Females observe these displays when choosing a mate.
Purpose of the Courtship Display
The plunging dives and flashy shows serve several purposes for attracting a mate:
- Gets the female’s attention
- Shows off the male’s athleticism and fitness
- Demonstrates the male has a good territory with flowers and nest sites
- Highlights the male’s colorful plumage
By boldly courting females with their elaborate aerial displays, male Anna’s hummingbirds ensure they mate with the most fit, colorful females to have the healthiest offspring.
Mating Behavior
Once a male’s courtship display succeeds in attracting a mate, the actual process of mating is quite quick.
The male and female perch close together on a branch facing each other. The male then swiftly mounts the female and inserts his two-lobed cloacal opening containing sperm into the female’s cloaca where her eggs wait. This cloacal kiss, called a cloacal contact, immediately fertilizes the eggs.
Mating lasts just a few seconds. The male then swiftly flies off again to continue displaying and mating with other females. The female gets straight to work on building a nest and laying her clutch of two tiny white eggs over the next few days.
Nesting and Raising Young
Anna’s hummingbird females do all the work when it comes to making nests, incubating eggs, and raising the chicks. Here is the nesting timeline:
Nest Building
Nest construction begins within a week after mating. The female gathers soft plant down, spider silk, lichens and moss and builds a tiny 1.5 inch wide cup nest on the branch of a tree or shrub.
She skillfully weaves the materials together and camouflages the outside with bits of bark, moss and lichen from the surrounding vegetation. This helps the nest blend in and avoid predators.
Egg Laying and Incubation
The female lays two tiny white eggs about the size of a coffee bean. She incubates them for about 16-18 days while defending the nest from other hummingbirds who might attack the eggs. She leaves the nest only briefly each day to drink nectar and catch insects.
Raising the Chicks
Once the eggs hatch, the female spends the next 3-4 weeks feeding her two chicks a diet of regurgitated nectar and insects. The chicks grow quills and feathers and are nearly adult size when they leave the nest and fledge at around 21-25 days old.
The female continues caring for her fledglings for another week or two by feeding them as they learn to fly, forage, and become independent.
Geographic Variation in Breeding Season
While Anna’s hummingbirds generally follow the November to July breeding timeline across their range, there are some differences depending on latitude and climate:
Location | Breeding Season |
---|---|
Southern California, Arizona | Mid November to late May |
Central California | Late November to late June |
Pacific Northwest Coast | Late January to late July |
British Columbia | February to August |
The farther north, the later nesting starts in spring. Southern range birds start breeding as much as 3 months sooner than those along the northern Pacific Coast. But the overall season length is similar across regions.
Impact of Climate Change
Some research indicates climate change may be shifting when Anna’s hummingbirds nest each year, especially in parts of their range where warm springs are arriving earlier.
A 2019 study from the University of Arizona examined nesting data going back to the 1970s for Anna’s hummingbirds at different latitudes along the Pacific Coast. It found birds are nesting earlier in the year now compared to decades ago.
On average, Anna’s hummingbirds are nesting about 26 days earlier in Washington state now versus the 1970s. In southern Arizona, nesting is 18 days earlier than historical norms. This shift correlates with warmer spring temperatures arriving several weeks earlier along the Pacific Coast in recent decades.
Earlier nesting may help birds take advantage of earlier spring flower blooms and insect hatches. It can ensure young fledge at the optimal time when food is abundantly available in summer. But if climate shifts get too far out of sync with food sources, reproduction success could suffer in the future.
Key Facts About Anna’s Hummingbird Mating and Nesting
Here are some key facts to remember about the breeding ecology of Anna’s hummingbirds:
- Breeding season lasts from November to July depending on latitude
- Courtship displays help males attract females from November to March
- Females build nests from February to early May
- Eggs are incubated for 16-18 days
- Chicks fledge about 3 weeks after hatching
- Climate change is shifting nesting earlier in spring
- Abundant flowers, long daylight, and mild weather enable breeding success
Conclusion
Anna’s hummingbirds have a relatively defined annual mating and breeding cycle timed to match optimal conditions along the Pacific Coast. Their reproduction is centered around the winter and spring months when flowering plants provide food, daylight hours are long, and weather is mild.
Males perform elaborate courtship plunges to attract mates from late fall through early spring. Once mated, the females assume all parental duties of nest building, incubating eggs, and raising the chicks through fledging in summer.
Ongoing research will continue to reveal how breeding phenology shifts in response to climate and habitat changes for these iconic and highly specialized birds.