Anna’s hummingbird (Calypte anna) is a small, iridescent green and pink hummingbird that is a year-round resident of the chaparral and woodland habitats of coastal California and Baja California. Here we explore the fascinating nesting habits of this tiny bird.
When does Anna’s hummingbird nest?
Anna’s hummingbirds can nest at any time of year, but the peak breeding season is between December and April. They may raise up to three broods per year. The timing of nesting coincides with the blooming of nectar-rich flowers that provide food for the adults and developing chicks.
Where does the Anna’s hummingbird build its nest?
Anna’s hummingbirds nest in a wide variety of sites, but they prefer trees and tall shrubs that provide cover and support for their tiny nests. Favorite nest sites include:
- Oaks
- Eucalyptus
- Cypress
- Pines
- Acacias
- Mimosa
- Pepper trees
- Cottonwoods
- Willows
The nest is usually placed on a downward sloping branch, between 3-20 feet off the ground. Anna’s hummingbirds sometimes nest at even greater heights in tall trees.
What is the Anna’s hummingbird nest made of?
The female Anna’s hummingbird constructs the tiny, delicate nest completely on her own. She selects a foundation branch and builds the nest in the shape of a compact little cup. The outside of the nest is camouflaged with pieces of bark, lichen, dried leaves and spider webs. These materials allow the nest to blend in with its surroundings.
The inside of the cup is lined with incredibly soft plant down collected by the female as she rubs her belly on plant seeds and dried plant fluff. The end result is an expandable, weather resistant nest perfectly shaped to hold the eggs and shelter the growing chicks.
What is the step-by-step nest building process?
Building an Anna’s hummingbird nest takes 6-10 days and involves the following steps:
- Select a nest site: The female hummingbird chooses a secure, hidden site, often quite high in a tree or shrub.
- Make the outer shell: The female collects plant fibers, spider silk, bark, lichens andBind these materials together with lots of spider web silk to form a secure, expandable outer cup.
- Line the inside: The female gathers incredibly soft plant down by rubbing her belly on seeds and plant fluff. She shapes this into a neat, warm, padded inner lining.
- Add structural support: The female weaves in twigs, bark strips or leaves to help stabilize the nest walls and provide attachment points.
- Camouflage the outside: The female disguises the nest with bark, lichens, spider web and chewed plant fragments that match the surrounding vegetation.
- Inspect and adjust: The female tests the nest by sitting in the cup. She adjusts the structure as needed before laying her eggs.
This intricate nest building process demonstrates the incredible instincts and capabilities of the tiny Anna’s hummingbird.
How big is an Anna’s hummingbird nest?
Anna’s hummingbird nests are absolutely tiny! They measure approximately 1.5 inches wide by 1.5 inches tall once completed. The nest cup is roughly 1 inch deep and 1.5 inches across.
The minuscule size of the nest matches the diminutive dimensions of the hummingbird. An adult Anna’s hummingbird measures only 3 to 4 inches long and weighs just 3-6 grams.
Constructing such a compact yet sturdy nest structure is an amazing architectural feat for such a small bird.
How many eggs does the female Anna’s hummingbird lay?
The female Anna’s hummingbird lays just 2 tiny white eggs per clutch. The eggs measure less than 0.5 inches long but represent almost a quarter of the female’s weight at laying.
The eggs are laid 1-2 days apart. Their perfectly oval, tapered shape allows them to wedge securely in the tiny nest cup.
How long does incubation take?
The female Anna’s hummingbird incubates her eggs alone. She sits on the nest for around 14-19 days before the eggs hatch. To conserve energy, the female enters a state of torpor at night where her metabolic rate slows dramatically.
During the day the female must leave the nest regularly to feed. She is able to precisely regulate the temperature and humidity within the nest to provide ideal conditions for embryonic development.
Who feeds the chicks?
Both adult female and male Anna’s hummingbirds are involved in caring for the chicks after hatching. The tiny chicks are almost naked and blind at birth but grow quickly on a diet of regurgitated nectar and insects provided by the parents.
Some key facts about chick rearing include:
- The female alone incubates the eggs and broods the hatchlings
- The female provides most of the food at first with the male visiting occasionally
- Both parents feed the chicks regurgitated nectar and tiny insects
- The chicks are brooded by the female at night and on cooler days
- The male assists more with feeding as the chicks grow
- The chicks fledge at 20-25 days old
This shared parenting improves the survival chances of their helpless offspring.
How do the chicks fledge?
Anna’s hummingbird chicks grow incredibly fast. They sprout dark gray feathers at around 10 days old and are essentially fully feathered by 15 days of age. Their wing feathers are still very short at this stage.
Over the next week, the chick’s wings rapidly lengthen until they reach full adult size. At 20-25 days old, the nestlings are ready to fledge.
On their first flight, the young hummingbirds only fly short distances. They return to continue begging parental care from their parents for another 7-14 days.
The incredible speed of nestling development means that Anna’s hummingbirds can raise 3-4 broods during a single breeding season.
Do Anna’s hummingbirds reuse nests?
Anna’s hummingbirds occasionally reuse a nest for a second brood in the same season, but this is rare. Far more often, the female builds a new nest from scratch for each brood.
Nests deteriorate quickly in the elements and expanding a weathered nest to accommodate a new brood takes as much energy as weaving a new structure.
Old Anna’s hummingbird nests are rarely reused in subsequent years. Any surviving nests are often knocked down by winter storms or decay through the year.
How many broods does an Anna’s hummingbird have per year?
Anna’s hummingbirds can raise up to 3-4 broods per year during the breeding season. The number of broods depends on the favourability of conditions, including:
- Availability of food sources
- Climatic conditions
- Health and energy reserves of the mated pair
- Predation pressures
Here is a summary of the potential reproductive scenarios:
| Broods per year | Scenario |
|---|---|
| 1 brood | Poor conditions such as limited food, bad weather, high predation |
| 2 broods | Typical year in many areas |
| 3 broods | Excellent conditions with abundant food, mild weather, low predation |
| 4 broods (rare) | Optimal conditions across the entire breeding season |
The high number of potential broods allows the Anna’s hummingbird to produce plenty of offspring across a range of conditions.
Do males and females mate for life?
No, Anna’s hummingbirds are polygamous breeders. This means:
- Males mate with multiple different females each season
- Females also mate with multiple males
- Pairs form temporarily during mating
- Males do not contribute to parental care after mating
- Females raise the chicks alone or with intermittent help from the male
This promiscuous mating system maximizes reproductive success for both sexes. Males can father more offspring by mating widely. Females can ensure high genetic diversity for their chicks by soliciting matings from multiple males.
Do males participate in raising chicks?
Male Anna’s hummingbirds play a minimal role in parental care. Their involvement includes:
- Visiting and occasionally feeding chicks raised by a female they mated with
- Assisting more with feeding older nestlings
- Displaying territorial defense against intruders
- Advertising food resources within their territory by conspicuous displaying
Despite their limited input, the male’s contribution can improve chick survival. This is especially true if the female struggles to find sufficient food for her fast growing brood.
How many chicks survive to fledging?
Anna’s hummingbird nests have a relatively high failure rate. Across all nesting attempts, an estimated 60% of nests fail to produce any fledglings.
For successful nests that do fledge young, the number of chicks is typically:
- 1 chick – 70% of successful nests
- 2 chicks – 30% of successful nests
The key reasons for nest failures and chick mortality include:
- Predation – eggs and chicks lost to jays, owls, squirrels etc
- Weather – nests damaged by wind and rain
- Disturbance – nests abandoned due to human activity near the site
- Insufficient food – starvation especially in poor weather when food is scarce
Despite these risks, Anna’s hummingbirds have survived by producing multiple broods and minimizing time spent vulnerable in the nest.
Conclusion
The Anna’s hummingbird has developed some amazing nesting behaviors to thrive in its specialized ecological niche. Key adaptations include:
- Building a structural marvel of a nest with spider silk and feather-soft lining
- Laying incredibly small eggs for their body size
- Entering torpor at night to conserve energy while incubating
- Having the versatility to triple clutch with up to 4 broods per season
- Reducing nest time with extremely fast chick growth and development
These traits minimize the risks of their small size and enable Anna’s hummingbirds to successfully raise young, even in challenging environments like coastal California. Careful placement of their exquisite tiny nests ensures the future of this captivating species.
