Anna’s hummingbirds are a small yet vibrant species of hummingbird found along the west coast of North America. Their brilliant iridescent coloring makes them stand out, even among other hummingbirds. But just how many Anna’s hummingbirds are there? Let’s take a look at what we know about this bird’s population.
How many Anna’s hummingbirds live in the United States?
According to the North American Breeding Bird Survey, there are an estimated 4 million Anna’s hummingbirds living in the United States. The species is most abundant in California, where over 75% of the U.S. population resides. Smaller populations can be found in Arizona, Oregon, Washington, and Nevada.
Anna’s Hummingbird Population in California
California is home to the majority of the Anna’s hummingbird population in the U.S. The California Partners in Flight Landbird Conservation Plan estimates the state population at over 3 million. Along the Pacific Coast, Anna’s hummingbirds can be found year-round. Inland populations tend to be migratory, arriving in early spring and departing in late summer or early fall.
Population Estimates for Other Western States
| State | Estimated Population |
|---|---|
| Arizona | 100,000 – 500,000 |
| Oregon | 50,000 – 100,000 |
| Washington | 50,000 – 100,000 |
| Nevada | 10,000 – 50,000 |
Smaller populations of a few thousand or less also occur in Idaho, Montana, New Mexico, Texas, and Utah.
What is the global population of Anna’s hummingbirds?
The global range of Anna’s hummingbirds is limited to the west coast of North America. They are found nowhere else in the world. So the population estimates for the United States likely represent the entire global population of the species.
Why is an accurate population count for Anna’s hummingbirds difficult?
There are a few factors that make it challenging to precisely determine the population size of Anna’s hummingbirds:
- They are small, fast-moving birds that are hard to accurately survey.
- Populations fluctuate throughout the year due to seasonal migration.
- Their habitat range is patchy, making extrapolation difficult.
- Population estimates typically rely on indirect calculation methods.
Because of these difficulties, most population figures represent educated guesses rather than precise counts. The estimates provide a good general sense of abundance, but the true population could be somewhat lower or higher.
How has the Anna’s hummingbird population trended over time?
By most accounts, Anna’s hummingbirds have experienced a moderate population increase over the past few decades. The North American Breeding Bird Survey detected a survey-wide population increase of 1.7% per year from 1966 to 2015. This upward trend was observed in California, Arizona, Oregon, and Washington.
Several factors may contribute to the increase in Anna’s hummingbirds:
- Expansion of urban and suburban areas providing bird feeders, ornamental flowers, and gardens
- Increasing temperatures due to climate change allowing northward expansion
- Adaptability to disturbed habitats
As long as adequate habitat, food sources, and nesting sites remain, Anna’s hummingbird populations are likely to remain stable or continue increasing slightly in the future.
How does Anna’s hummingbird reproduction impact population levels?
The reproductive habits of Anna’s hummingbirds allow populations to rapidly bounce back from dips or declines. Here’s how their breeding behaviors help maintain robust populations:
- Females produce multiple broods per year, with 1 to 3 eggs per clutch
- Nesting season lasts up to 7 months in California
- Females continuously nest and lay eggs until late summer
- High nest success rates around 65%
- Short 18-20 day nesting period
With this high reproductive output, Anna’s hummingbird populations can quickly rebound even after events like severe storms, cold snaps, or drought that may temporarily suppress numbers. Their high reproduction rate helps keep populations stable.
Clutch Size and Nesting Cycles
On average, female Anna’s hummingbirds lay 1-3 eggs per clutch. The table below shows some observed clutch size frequencies in California:
| Clutch Size | Frequency |
|---|---|
| 1 egg | 1.7% |
| 2 eggs | 84.2% |
| 3 eggs | 14.1% |
Females may go through 3-5 nesting cycles per season, allowing for high productivity even with modest clutch sizes.
Nesting Success Rates
Reported nest success rates for Anna’s hummingbirds are fairly high at around 65%. This table shows success rates from a California study:
| Nest Outcome | Percentage |
|---|---|
| Successful fledging | 65.3% |
| Predated | 12.2% |
| Abandoned | 9.2% |
| Nonviable eggs | 7.6% |
| Other failures | 5.7% |
This high nest success rate contributes to positive population growth.
What threats face Anna’s hummingbird populations?
Though still relatively abundant, Anna’s hummingbirds do face a few threats to their continued population health:
- Habitat loss from development
- Climate change impacts
- Drought reducing food availability
- Nest parasites and predators
- Collisions with buildings and towers
- Competition with invasive bird species
Fortunately, Anna’s hummingbirds remain common over much of their core range. But habitat conservation efforts, reduction of climate threats, and public education can help maintain populations into the future.
Habitat Loss
Development reduces the open scrublands and forest edges preferred by Anna’s hummingbirds for nesting and feeding. As human settlement expands along the west coast, maintaining adequate habitat will require conscientious conservation planning.
Climate Change
Climate change may increase the risk of heat stress, drought, severe weather, and fires that can impact hummingbird populations. Providing artificial food and water sources can help counter these effects. Reducing greenhouse gas emissions remains critical.
Invasive Species
Introduced bird species like European starlings compete with native cavity nesters like Anna’s hummingbirds for limited nesting sites. Monitoring and managing invasive populations helps protect habitat for native birds.
Conclusion
Current population estimates put the total number of Anna’s hummingbirds living along the west coast of North America at around 4 million, with over 3 million in California alone. Through adaptations like high reproduction and the ability to thrive in urban settings, Anna’s hummingbird numbers remain healthy compared to historical levels. Maintaining ample natural habitat and food sources will ensure these iconic and beloved birds continue brightening the landscape with their vibrant beauty.
