Hummingbirds are some of the smallest and most remarkable birds in the world. Known for their ability to hover in midair and fly backwards, hummingbirds have captured the fascination of people for centuries. Of the many hummingbird species, Anna’s hummingbird (Calypte anna) is one of the most common in North America.
About Anna’s Hummingbirds
Anna’s hummingbird is named after Anna Masséna, Duchess of Rivoli. A medium-sized hummingbird species found along the Pacific Coast from British Columbia to Baja California, Anna’s hummingbirds are dark green and grey in color with iridescent rose-pink throats and crowns. The males have a distinctive magenta crown and throat feathers that appear black unless struck by direct sunlight. Females lack iridescent throat feathers and have grey crowns and throats.
Preferred habitats for Anna’s hummingbirds include gardens, parks, and backyards, especially those that provide nectar-bearing flowers and trees. They are adapted to urban settings and do well around human development. Anna’s hummingbirds feed on nectar, sap, and small insects. To conserve energy, they go into torpor (temporary hibernation) at night and on cool days.
One unique aspect of Anna’s hummingbirds is their ability to thrive in cold temperatures. They are the only hummingbird species found regularly in Canada and some northern U.S. states. Their feathers help insulate them in freezing temperatures. Anna’s hummingbirds also begin breeding earlier than any other North American hummingbird. They can produce two broods in a season starting as early as December.
Population and Conservation Status
Determining exact population numbers for Anna’s hummingbirds is challenging. As with most bird species, conducting comprehensive surveys across their entire range is logistically difficult and requires substantial time and resources. However, some estimates can be made based on available data:
- The global breeding population is estimated at over 4 million birds.
- In British Columbia, population estimates range from 50,000 to 100,000 breeding pairs.
- California hosts the largest population with an estimated 1.5 million Anna’s hummingbirds statewide.
- There are approximately 25,000 to 100,000 Anna’s hummingbirds in Baja California.
Despite being one of the most common backyard hummingbirds, Anna’s hummingbird populations saw concerning declines in the 1960s through the 1980s due to habitat loss and widespread use of pesticides. However, thanks to conservation efforts and bans on harmful chemicals like DDT, their numbers rebounded in the 1990s. Currently, their global population trend is listed as stable by the International Union for Conservation of Nature (IUCN). Their abundance and adaptability to human environments make them a species of Least Concern.
Breeding and Reproduction
The breeding habits of Anna’s hummingbirds lend insights into their total population numbers. Key facts about their reproduction include:
- Females typically lay 2 eggs per clutch, with 1 to 3 clutches per season.
- Only the female incubates the eggs, for about 16 days.
- Chicks fledge about 3 weeks after hatching.
- Females raise the chicks alone without the male’s assistance.
- Pairs may re-nest up to 4 or 5 times from December to June.
Based on a reproductive capacity of 2 eggs per clutch and 3 clutches per season, each breeding female Anna’s hummingbird can produce about 4 to 6 offspring annually. Only about 50% survive their first year. Adult hummingbirds have fairly high survival rates at around 60%. By combining these reproductive and mortality rates, we can estimate the population growth potential for the species. With adequate food supplies and limited predation, Anna’s hummingbirds appear capable of maintaining stable or even increasing populations through their breeding output.
Population Distribution
Anna’s hummingbirds are found along the full length of the Pacific Coast, from southern British Columbia in Canada to Baja California in Mexico. Their range extends inland to the west slopes of the Rocky Mountains from southern Alberta to southern Arizona and New Mexico. Within this broad region, they are permanent residents in some areas while temporary summer residents in other parts of their range.
Here is an overview of their population distribution across different states and provinces:
State/Province | Breeding Population Estimate | Seasonal Presence |
---|---|---|
British Columbia | 50,000 – 100,000 pairs | Summer breeding resident |
Alberta | 10,000 – 50,000 pairs | Summer breeding resident |
California | 1 million to 1.5 million | Year-round resident |
Arizona | 50,000 – 100,000 | Summer breeding resident |
Baja California | 25,000 – 100,000 | Year-round resident |
As the table shows, California contains the bulk of the global Anna’s hummingbird population. The combination of an extended breeding season and abundant natural food sources allows their numbers to flourish in the state. British Columbia and Baja California also support significant populations during summer nesting and year-round, respectively.
Tracking and Monitoring
Conservation groups use different methods to track Anna’s hummingbird populations. Some key initiatives include:
- Breeding Bird Surveys: Since 1966, annual surveys have been conducted along roadside survey routes to monitor breeding bird population trends, including for Anna’s hummingbirds.
- Christmas Bird Counts: Volunteer birdwatchers perform annual winter bird counts which provide winter population data on Anna’s hummingbirds across their range.
- Migration Monitoring: Networks of bird banding stations along the Pacific Flyway gather migration timing data on banded Anna’s hummingbirds.
- Feeder Surveys: Projects like the Cornell Lab of Ornithology’s Project FeederWatch enlist citizen scientists to count birds at backyard feeders.
- eBird: This real-time, online checklist program compiles millions of bird sightings submitted by birdwatchers, creating a vast data source for population modeling.
Researchers combine the results of these different surveys and citizen science initiatives to estimate Anna’s hummingbird populations and track their distribution and migration patterns. The advent of technologies like online reporting tools and data visualization has enhanced experts’ ability to monitor hummingbird numbers across their range.
Range Shifts
Tracking data has revealed some noteworthy shifts in Anna’s hummingbirds’ range in recent decades. These include:
- Northward expansions along the Pacific Coast into Alaska starting in the 1970s.
- Increases inland into Nevada, Utah, and Colorado as breeding season residents.
- More overwintering farther north along the Pacific Coast into Oregon and Washington instead of migrating south.
Researchers believe warmer temperatures in these northern areas may allow Anna’s hummingbirds to expand their range by providing adequate food supplies and reducing risk of freezing. This illustrates how monitoring data continues to provide new insights into hummingbird distribution and adaptations.
Threats and Conservation Challenges
The majority of Anna’s hummingbirds thrive among human development in suburban neighborhoods, parks, and gardens. However, some key threats to their populations remain:
- Habitat loss: Agricultural and urban expansion eliminates native flowering plants needed for nectar and nest sites.
- Pesticides: Chemicals can accumulate in the insects and nectar hummingbirds consume.
- Climate change: Shifting precipitation patterns and plant blooming times may limit food availability.
- Window collisions: Hummingbirds are prone to colliding with windows on buildings.
Conservation measures for Anna’s hummingbirds include planting native flowers and shrubs, reducing pesticide usage, installing decals to prevent window strikes, and educating the public. Climate change remains the most challenging long-term threat to address. Maintaining habitat connectivity so hummingbirds can track suitable conditions will grow increasingly vital.
Conclusion
With an estimated global population in the millions, Anna’s hummingbird remains one of the most prolific and recognizable hummingbird species in the U.S. and Canada. Thanks to dedicated monitoring programs and citizen scientists, researchers can track Anna’s hummingbird population trends and distribution across the full extent of their range along the Pacific Coast. Although still dependent on habitat availability and vulnerable to climate disruptions, Anna’s hummingbirds demonstrate resilience in the face of urban expansion and human activity across much of their range. Maintaining healthy native plant communities and reducing pesticide usage will be key to ensuring these tiny, glittering birds continue brightening yards and gardens for years to come.