Anna’s hummingbirds (Calypte anna) are small, beautiful birds found along the Pacific coast of North America. Known for their iridescent throats and speedy flight, these tiny birds have captured the fascination of birders and nature lovers alike. One aspect of Anna’s hummingbird life history that generates a lot of interest is their breeding habits – specifically, how often they lay eggs each year. In this article, we will explore what is known about the egg-laying frequency of Anna’s hummingbirds.
Anna’s Hummingbird Breeding Overview
Anna’s hummingbirds breed between November and June, with the peak of their breeding season occurring between mid-March and early May. They are territorial birds that nest in open woodlands, gardens, and parks from southern British Columbia to Baja California. The male Anna’s hummingbird performs elaborate courtship displays, flying in U-shaped or J-shaped dives to attract a female. Once paired, the female builds a small, compact nest out of plant down, spider webs, and lichens on the branch of a tree or shrub. She lays a clutch of just two tiny white eggs, which she incubates for 16-17 days while the male continues to feed her. The chicks hatch out almost naked, with their eyes sealed shut, and are fed by the female for 23-26 days until they fledge from the nest. Anna’s hummingbirds are solitary nesters, with each female caring for her own nest without help from the male.
How Many Broods Per Year?
So during this breeding season from November to June, how many times does the female Anna’s hummingbird lay eggs? The answer is that she can produce up to 3-4 broods per year. Each brood involves building a nest, laying 2 eggs in that nest, incubating them, and raising the young. Here is a breakdown of the Anna’s hummingbird’s potential breeding cycle throughout the year:
- First brood: November to January
- Second brood: February to March
- Third brood: April to May
- Fourth brood: May to June
As you can see, there are four potential brood periods within their breeding season. However, successfully raising three or four broods from start to finish is challenging for the female. Let’s take a closer look at how many broods Anna’s hummingbirds typically complete each season.
Typical Number of Broods
While female Anna’s hummingbirds may initiate up to four nests per year, most evidence indicates they are only able to successfully complete 2-3 broods on average. Here are some reasons why their success rate is lower than their potential maximum brood number:
- Building a nest, incubating eggs, and raising hatchlings to fledging is an enormous energy expenditure for the small hummingbird.
- Nests are often predated by jays, squirrels, and other animals, forcing the parents to abandon the eggs and start over.
- As the breeding season progresses, fewer flowers are in bloom, making it harder for the parents to get enough food.
- Late season broods may fledge too late for young birds to mature and prepare for winter migration.
These challenges mean that while Anna’s hummingbird females lay 2 eggs 4 times per breeding season hypothetically, in practice most will only be able to raise 2-3 broods to independence each year.
Geographic Differences in Brood Number
Studies of banded Anna’s hummingbirds have shown some geographical differences in average annual brood numbers:
Location | Average Broods Per Year |
---|---|
British Columbia | 2 |
Pacific Northwest | 2-3 |
California | 3-4 |
Baja California | 3-4 |
The more northern parts of their range, such as British Columbia, have a shorter breeding season and fewer blooming flowers available to fuel reproduction. The warmer southern areas like California and Mexico can sustain a longer breeding season and more successful broods per pair. However, even in ideal habitats, raising the maximum of four broods is rare due to the aforementioned challenges.
Individual Variation in Egg Laying Frequency
While the average number of broods provides helpful insight into Anna’s hummingbird breeding patterns, there can also be significant individual variation among different females. Here are some factors that can influence an individual bird’s egg laying frequency in a single season:
- Age – Younger females in their first year of breeding often raise only 1-2 broods, while older more experienced females can manage 3-4.
- Health – A healthy, robust female with a territory rich in flowers will lay more broods than a weaker or less fit bird.
- Weather – Unusually cold or wet weather can suppress insect food sources and flowering, reducing brood success.
- Predators – High predator densities may force more re-nesting attempts.
- Luck – Chance calamities like nest destruction can truncate a female’s season.
So while the average gives us a good baseline, each female Anna’s hummingbird may end up laying anywhere from 1-4 clutches based on a wide range of biological and environmental factors. Tracking banded birds over several seasons can provide better data on each bird’s typical reproductive success.
Lifetime Reproduction
In addition to looking at reproduction within a single breeding season, we can consider Anna’s hummingbird’s lifetime egg laying habits. The maximum recorded lifespan of an Anna’s hummingbird in the wild is 12 years. Over that time, roughly how many eggs might an individual female lay in total?
To arrive at a very rough estimate, let’s assume an average of 3 broods per year, 2 eggs per brood. Over 12 years, that would mean:
- 12 breeding seasons
- 3 broods per season = 36 broods
- 2 eggs per brood = 72 eggs
That provides an estimate of approximately 72 eggs laid over an Anna’s hummingbird’s lifetime. Of course many would produce far fewer eggs over shorter lifespans of just 2-6 years. But those longer-lived individuals may lay eggs into the hundreds over more than a decade of breeding.
Why Egg Laying Frequency Matters
Understanding the reproductive strategy of Anna’s hummingbirds provides insight into their biology, habitat needs, and potential responses to environmental changes. Specifically:
- Their high egg laying frequency requires abundant nectar and insect food sources all season long.
- Their reliance on multiple broods means they need protected nesting sites and minimal predation.
- Their energy expenditure for breeding makes them vulnerable if climate change disrupts flower/insect cycles.
- Conservation plans must account for the resources needed to sustain their reproductive output.
In sum, the potential for up to 4 clutches per year, 2 eggs per clutch, demonstrates how Anna’s hummingbirds are set up to reproduce often and abundantly under ideal conditions. Providing the habitats and ecological resources to enable this high rate of reproduction should be a priority for anyone interested in sustaining healthy populations of these special birds into the future.
Conclusion
To conclude, female Anna’s hummingbirds have the capacity to lay up to 4 clutches of 2 eggs per year from November through June. However, successfully fledging 3-4 broods is rare due to the immense energy demands of breeding. On average, a female Anna’s hummingbird will complete 2-3 broods per season, with a range of 1-4 under variable individual circumstances. Understanding the drivers behind their high annual egg laying rates provides critical insight into their habitat requirements and guides appropriate conservation actions. With the right resources available, Anna’s hummingbirds will continue gracing the Pacific coast with their beauty and incredible hovering flight through persistence of their delicate yet resilient life cycle.